Greetings!

I just opened this up today and it's certainly new ground for me. The oldest thing I have redone is a '72 Sansui stereo amp receiver. This is really amazing. It's Oooold! Any input would be greatly appreciated. Some things that come to mind are what not to use for chemicals if any. I'm not sure if it's OK to use Deoxit or denatured alcohol even. Some of these parts look more like Halloween candy. (BTW, notice my snack in the upper right hand corner of the first pic.) Should I replace the caps with modern electrolytes or go to polyprope or???? Other parts I have never seen before; I have no idea what they are. But I'll go a step at a time.

Any help? 'Looks like fun to me.

I don't see any of your pictures :headscrat

Oooops

Ah, much better :D

Cool radio - early 30s I believe. Looks to be in rally good condition.
Just about all of the cylindrical parts you see below are capacitors. A few are resistors like the big yellow bugger with an orange spot on the right - AKA a "dogbone".
I'd use polys for all the caps below including the two metal box caps.
Modern electros for the two big caps on top.

Thanks much for the information. Underneath, what is that brown square object with the multi colored dots on it?

Thanks much for the information. Underneath, what is that brown square object with the multi colored dots on it?

Glad to help. That's a molded mica capacitor. They rarely go bad so I'd leave it alone. Check out these links for the color code:
http://www.vcomp.co.uk/components/cap_codes/cap_codes.htm
http://www.radioremembered.org/capcode.htm

Fantastic!

.. a couple very general but necessary questions before I start this project...

Are there any abnormally toxic materials that could be found in parts of this period?

Are there any bad combinations of chemicals that I should avoid either that could be hazardous or could cause damage to these wonderful ancient artifacts?

and.. is there anything that is delicate that I should just leave completely alone?

Thanks again...

The yellow colour of the chassis comes from cadmium plating. It is quite poisonous, so wash your hands after handling the chassis. Other than that, the solder is partly lead. This accounts for most of the toxic materials.

Whew, good to know. I noticed that part of this chassis has a greening look to it. Mold? Copper? Arsenic???

Whew, good to know. I noticed that part of this chassis has a greening look to it. Mold? Copper? Arsenic???

That's probably cadmium oxide too. I've been running into it a lot lately. I posted a thread about how to remove that oxide and polish it up. As amptramp said, it's toxic so beware!

If you're wondering why they used it - it's prevents rust, is easy to solder to and looks nice. At least at first.

http://www.videokarma.org/showthread.php?t=246991&page=2

There is one of those languishing in a warehouse here in Lancaster. It's a big junk shop and they have about a half dozen old consoles rotting away there. While they are way overpriced, I did buy my first tube powered radio there (an RCA) the GE was my second choice, as I liked the drum-shaped tuner. For a first restoration, this should be an easy one-not a lot to replace, and a very open, easy to work with chassis design.

That's great news. It looks like a really interesting fix-up.

I am making a parts list for replacement and there are 2 silver paper board boxes on the underside that have familiar markings but unfamiliar presentation:

One says - 4mF 450V GEP-5, 3mF 150V DGP-2
The other says - 450-25V 4-10mF, SGP-2 CCCW

They sound like caps but what does it mean when boxed like this? I can't see what's inside and one is riveted to the chassis.. and the GEP, DGP, SGP are unfamiliar. My guess is the CCCW is 300 watts??

help?

One says - 4mF 450V GEP-5, 3mF 150V DGP-2
The other says - 450-25V 4-10mF, SGP-2 CCCW



Each of these boxes contain two capacitors. The first one has a 4uF at 450V and a 3uF at 150V. The second box has a 4uF at 450V and a 10uF at 25V. I am not familiar with the GEP-5, DGP-2, SGP-2, or CCCW. I would guess they are manufacturer part numbers.

If you haven't found a schematic for this set you might try this one:
http://www.nostalgiaair.org/PagesByModel/754/M0007754.pdf
Nostalgia Air does not have a listing for the A-66 (other than 1 page in the Changes section of Riders). I am assuming the 6-14 on one of the silver boxes was put there by someone who had worked on this set previously. It corresponds to a Riders manual page for the A-64 and A-67 models.

Those mid 1930s GE sets are very good performers and are very well built. They are under appreciated by collectors.

Thanks for the map! I had no idea things like that were still around.

I promise to stop bothering you guys as soon as I can get my chicks in order but I was wondering, where does one find some of these caps? E.G. 16uF and 8uF @ 500V and some of those other high voltage things? I can only find 450 to 475 in those 8 and 16uF caps. The others I can basically find but it's a mishmash polyprope, polystr, metal film and small electrolytic. Some have to have much higher voltage ratings to fit the uFs. I looked at Mouser and DigiKey.

The other thing are those dogbones. I have a pretty good idea how they read but not in any really solid way, just an old chart that's from the 40's. Is there a solid chart or explanation that can be relied upon with no discrepancies with the Philco versions?

I've never fished these waters before...

Thanks

I believe all the old dog-bone resistors use the "BED" body,end,dot code...
More charts here:

http://www.vintageradio.me.uk/info/Componentinfo1.htm

Have fun!
jr

Why, son, that set ain't old. :D It even uses octal tubes, so it's from about 1936 or so. Many consider that era of '36 to '38 the peak of radio perfection.

Age of radio perfection.... If that's so, what can I use instead of a screwdriver?:D:D

Perfection may be hard to reach but pretty darn good is attainable. Dig right in!

I have this flexible resistor that I can't read on the schematic and I'm not sure how to read the code on it. My meter shows fluctuating readings sometimes 1.2Kohms sometimes 3.4K. It's one of those that looks like a cable with wire winding on the ends. It's brown with 2 painted stripes, green and gray. The gray one is a guess. It could be brown or silver but I have to bet on gray. No color on either end. The schematic is illegible on that particular item and the parts list shows 3 flexibles. I can only find this one on the radio. In the process of elimination, the radical meter readings just don't come close.

If someone could give me an idea how to read this thing, it would be greatly appreciated!

Thanks

... I promise to stop bothering you guys as soon as I can get my chicks in order but I was wondering, where does one find some of these caps? E.G. 16uF and 8uF @ 500V and some of those other high voltage things? I can only find 450 to 475 in those 8 and 16uF caps. The others I can basically find but it's a mishmash polyprope, polystr, metal film and small electrolytic. Some have to have much higher voltage ratings to fit the uFs. I looked at Mouser and DigiKey...
I've never fished these waters before...

Thanks

You can get 500v caps at justradios (http://www.justradios.com/cart.html) A 10uF should do fine for the 8uF cap.

I would assume that flexible resistors use the same color code as carbon resistors. The only one in the parts list that could match based upon the green stripe is R19 which is 450 ohms. I would think it would have yellow-green-brown stripes. Looking at where it is connected in the circuit would be a better way to determine which one it is. R19 is the cathode resistor for the 6F6 so would connect between pin 8 of the 6F6 and ground. R2 is the cathode resistor for the 6A8 and connects between pin 8 and pin 1 (ground) of the 6A8. R5 is the cathode resistor for the 6K7 and connects between pin 5 (5 is tied to 8) and ground.

Thanks Sean. That helps a lot.

I have another question. I'm a little dumbfounded about these dry cap packs with multiple ratings and voltage. How do you replace those? I've never seen this kind of thing before nor do I know what to use in their place. Is there a way to wire in 2 separate caps for each one? Honestly, I don't even know how they work like that.

I would really like to learn about this and take a stab at it.

Thanks!!

Thanks Sean. That helps a lot.

I have another question. I'm a little dumbfounded about these dry cap packs with multiple ratings and voltage. How do you replace those? I've never seen this kind of thing before nor do I know what to use in their place. Is there a way to wire in 2 separate caps for each one? Honestly, I don't even know how they work like that.

I would really like to learn about this and take a stab at it.

Thanks!!

I'm working on a few of those right now too. Check out my thread - I put up a bunch of pictures: http://www.videokarma.org/showthread.php?t=246672&page=5

You could just clip the wires going the old ones and solder new ones in.

If you want to try restuffing them, the first step is to unsolder the pack and remove it from the chassis. Then, you need to figure out how to get the old guts out.

The last few I've done had metal tabs I could bend back. A little heat loosen up the tar inside and the old caps slid out. Next, I used some lacquer thinner to clean out any remaining gunk. I soldered new polypropylene caps in place.

Finally, for a couple of them, I refilled them with commercial grade wax. A little foam stuffing or hot glue would work too. Just so the new ones don't flop around inside the box. Bend the tabs back over to reseal the box. Remount it and solder the wires to it.

The worst part is definitely all the tar :yuck:

Good luck
Bob

Thanks Bandersen. The ones I am talking about are in rectagonal silver cardboard boxes one of which is rivited to the chasis. One of them says, for instance, 4mF 450V GEP-5, 3mF 150V DGP-2 on the box which are 2 different caps. Upon opening, there is one large cylindrical clump of wax and tar that is wired green and red on one end and black connected to foil on the other.

Hmm

Thanks Bandersen. The ones I am talking about are in rectagonal silver cardboard boxes one of which is rivited to the chasis. One of them says, for instance, 4mF 450V GEP-5, 3mF 150V DGP-2 on the box which are 2 different caps. Upon opening, there is one large cylindrical clump of wax and tar that is wired green and red on one end and black connected to foil on the other.

Hmm

That makes sense. The black should be a common ground connection. The red and green will be the other end of the 4mF and 3mF capacitors. You'll need to consult the schematic and trace the wiring to determine which is which.

You can clip out that old lump of wax and tar and solder your new caps in there.

If you want to use poly caps, Mouser has some.

3mF @ 200v (http://www.mouser.com/ProductDetail/Cornell-Dubilier/935C2W3K-F/?qs=sGAEpiMZZMvCt%252bwg%252braTuv9D6Mg0ahlvQZIsQ9 AikuM%3d)

4.7mF @ 600v (http://www.mouser.com/ProductDetail/Cornell-Dubilier/940C6W4P7K-F/?qs=sGAEpiMZZMvCt%252bwg%252braTun41hzsAiBuHC6Dqcb v0Aas%3d)


Alternately, you could use a couple electrolytics.

Thank you so much... You know, I think I have it all figured out now (hope) and when the parts arrive it will be a go! I'll start working on the chassis with the Naval Jelly and get'er all cleaned up for the re-cap.

I'll be back with progress!

Hey guys... I'm back.

I have a problem. I've been pretty lucky in the past with computers and stereo rebuilding considering I am highly inexperienced in electronics. I've recapped many a mother board with success etc, but this!... this advanced tube technology... it's over my head I'm afraid. I am very willing and ready to learn though.

The A-66 is completely recapped. I replaced most of the resistors. I replaced all the wiring that was necessary which was 95% of it. I have stayed away from the coils except to replace absolutely necessary main wires so as to do as little disturbance to them as possible; I only replaced those wires by continuing from the old wiring about an inch off the coil's solder points. I have done the best I can to replicate the capacitors and resistors according to the specifications of the removed part.

With all tubes removed, I plugged into my PMV w/ a 60W bulb. It shows a short; there's no drop in the bulb brightness. Both power plug leads show no continuity with the chassis. With power on, I get 3.4V AC on the chassis.

Like I said before, I've been pretty lucky in the past but I guess here's my chance to learn some troubleshooting electronics. If anyone is willing to help, I would surely appreciate it.

Thanks! :ntwrthy:

I would suggest checking resistances of the windings in the power transformer with the power removed. Make sure they are close to what is shown on the schematic. Also measure resistance from the lead of one winding to one lead of each of the other windings to make sure there are no shorts between windings.

I'm not familiar with the term "PMV" but I would assume that this is what is commonly referred to as a "dim bulb tester"?

PMV = Poor Man's Variac

Yes

Thanks for the tip Sean. I made 2 preliminary readings but I also need to ask if I'm checking it correctly. I followed 2 of the wires that the schematic says are on a particular coil and did the same with another. Both lead to the power rectifier plug. That is where I took the readings. I don't know if that is the correct way to get that or not. On the schematic, one is supposed to be 200 Ohms and reads 380. The other is supposed to be .2 Ohms and reads .6 . I haven't dug around for the other 2 before I find out if I am doing this right.

If this is correct, then the transformer is shot I guess.

Any input? Thanks!

one other thing... there doesn't seem to be any short between those 2 coils using the same system I just explained.

and yet another update... Measuring from one end of the 200 Ohm coil to the chassis, I get 198 Ohms and on the other side of that coil wire I get 187. On the wire going to the .2 Ohm coil to the chassis I got .2 to .3 Ohms then I double checked it a minute later and I get no reading at all and haven't since. Hmmm :scratch2:

Have you disconnected the transformer secondary leads from the radio ? If they are still wired into the set when you take your measurements, you could be getting bad readings due to wiring or component problems down the line.

Nope! I had better do that. Thanks. 'taking one step at a time...

If you turn on the power switch and measure between the pins of the power plug you should get around 6.4 ohms. You should get an open circuit between either pin of the power plug and the chassis.

Between pin 4 of the 5Z4 socket and the chassis you should get about 200 ohms. Between pin 6 of the 5Z4 socket and chassis you should also get about 200 ohms. This seems to jive with what you mention in your last post.

Between pins 2 and 8 of the 5Z4 socket you should get 0.2 ohms. You should get an open circuit between either pin and the chassis.

Between pins 2 and 7 of the 6F6 you should get 0.2 ohms. Between one of these pins and the chassis you should have a dead short. Be sure to remove the dial light before taking measurements for this winding.

If you disconnect the center tap of the B+ secondary (winding connecting to pins 4 and 6 of the 5Z4) that should isolate all the windings from one another and you should not get any continuity between any of the windings.

On your PMV you do have the light bulb wired in series with the radio and not in parallel, right?

That's detail. I'll get to it.

Yup, the PMV is in series. I have used it many times for other projects. 'Works great.

Thanks

OK...

Your first and second paragraph tests out OK.

If I am counting the pins correctly on the 5Z4 (the schematic is illegible and marked with letters P1 P2 H S can't read the others) then I am getting between .5 and .6 ohms between pins 2 and 8.

On the 6F6, I get between .3 and .4 ohms between 2 and 7 (again if I am getting the pins right). Both pins are grounded to chassis as a matter of fact only pin #5 and #6 are not grounding to the chassis.

The dial light is clipped and pin #6 is disconnected on 5Z4

On the matter of the 6f6, here is a tube diagram of that little feller:

http://www.nostalgiaair.org/tubes/6f6.htm

pins 2 and 7 being the filament, you will pretty much have your multimeter reading as a short to ground for both of those pins while the tube is installed, as the filament is of very low resistance. If both pins 2 and 7 still read as a short to ground when the 6f6 tube is pulled, then you could have a problem.

On the issue of all of the other pins, save for 5 and 6 being grounded; pin 6 isn't used on this tube, though there may still be things soldered to it, being used as a tie point for other parts in the circuit. Pin 5 is the signal input grid, so that makes sense that it wouldn't be grounded. Looking at the schematic, it appears that pins 3,4, and 8 should not be grounded. But we'll mess around with that issue a bit more once your transformer issues are cleared up.

Guys.. Thanks for the help. I learned how to track down a circuit without a PC board. I was able to use the detail as well as the bits and pieces of info about tubes and the pin setup and I found 2 wiring mistakes, my mistakes of course, that put my PMV (dim bulb tester) to sleep!

The 60W dropped right back but it didn't start out very high as I am used to for getting those caps jump started. Then after about 2 seconds, I started to hear something very faint and my gut reaction was to flip the switch on the PMV which I did. It wasn't like a crackle or a fizz but more like a faint hiss. Anyway, there was no smell or smoke or heat that I could tell. I still have no tubs in, but that pin 2 and 7 on the 6F6 are still showing ground to chassis. After figuring out which pin is which... 3, 4, 6 and 8 are not grounded... 1, 2, 5 and 7 are. 6 isn't used.

Should I turn the thing back on? I'll wait for now.

I still have no tubs in, but that pin 2 and 7 on the 6F6 are still showing ground to chassis. After figuring out which pin is which... 3, 4, 6 and 8 are not grounded... 1, 2, 5 and 7 are. 6 isn't used.

Do you see a physical connection between pin 2 and the chassis and between pin 7 and the chassis on the 6F6 socket? If you are saying they are both grounded because of the resistance readings then you are measuring through the filament winding of the transformer (or a short circuit in the wiring). Disconnect the wires coming from the transformer from pins 2 and 7 on the 6F6 socket and measure between these two leads from the transformer. This measurement should be low (0.2 ohms according to the schematic). With these leads disconnected measure between pin 2 and pin 7 on the socket. This measurement should be open.

Pin 1 and either pin 2 or pin 7 should be grounded. Pin 5 should not be grounded. There should be about 500k ohms between pin 5 and ground due to the grid resistor.

With no tubes in it you aren't going to get any voltage on the electrolytics. The 5Z4 rectifier would need to be installed to get voltage to them. BTW, as a word of warning for when you get to this point don't ever run the radio with the 5Z4 installed without the speaker connected. Since the speaker has a field coil that is used as a filter in the power supply not having it in the circuit can cause the voltage to get too high on C13 and C14 and they can pop. Been there, done that.

The wires are disconnected and show .6 ohms. The measurement between 2 and 7 is open. The resistor between pin 5 and the chassis was a flexible one. I thought it was good but it wasn't. I replaced it with a 500K and now it shows no grounding. There is a physical connection to the chassis from pin 8 via a 500 Ohm resistor and is not grounded. There is a direct connection to ground from pin 1.

I guess what's at issue now is whether .6 ohms is close enough to the .2 ohms that is called for on that transformer coil; I wouldn't know. The other coil that is supposed to be .2 shows .4 and it connects to the panel lights if I remember correctly. (disconnected at the moment)

Oh.. and thanks for the 5Z4/speaker tip!!

I think those resistance measurements are fine. What is shown on the schematic is not going to take into account the resistance of your meter leads. What you might do now is to plug the chassis in without tubes and measure the AC voltage coming from the B+ winding. You would measure between pin 4 and the chassis and pin 6 and the chassis. Be careful with this measurement. The schematic shows about 370V AC from each pin to ground but it will probably be a little higher since the transformer isn't being loaded down. Also check the voltages on the filament windings. Between pin 2 and pin 8 of the 5Z4 you should get about 5V AC. Between pin 2 and pin 7 of the 6F6 you should get about 6.3V AC. If you start getting the hissing sound you mentioned earlier, try to see where it is coming from.

I powered up with the 60W bulb and I found the hiss and shut down. There is a small arch underneath the 5Z4 plug. But it doesn't look like it's between it and the chassis necessarily but the arc is coming from a small moon shaped hole that seems to be where the solder point for pin 5 would be if there was a pin 5; there is not a pin 5. I have no idea what it is or why it would happen but there is definitely a hot, smoking arc flashing from within that hole.

I'm curious-does the 60W bulb light up as a short during the hiss?

You'll need to order a new socket now-once that carbon starts to build up where it arced, it will continue to do so. Do not run that radio until you get that socket out of there.

I had a radio with a similar problem-a little bit of moisture was retained from when I had cleaned the chassis, it caused a small arc, and I had to pick up a new tube socket. Once I did that, the radio played perfectly.

Yes, the bulb lights up like a lamp. Thanks for the socket info. I suppose these are available at some of the antique radio sites. I'll look around. Maybe I should see if I can clean or dry out the others somehow. Blow drier?

The base of the 5z4 tube is the same as all of the other tubes in that set, right? If it is, then you'll need to find what is called an octal socket. Luckily, this has to be the most common socket type out there. There are plenty on ebay right now that could be had for less than a dollar.

You can still do a little more while you wait for your socket in the mail. Disconnect your transformer leads that run to the 5z4 socket. That should stop the arcing. The only thing that should be hooked up now is the filament string. You could try to light up the other tubes with the 5z4 unhooked to see if at least that part of the radio is functional.

As for drying out the chassis, it should probably be fine after sitting around for the couple of days that it would take for the new socket to arrive. Some folks may suggest putting it into an oven to dry it out, but that could cause other issues. Actually, some people claim to wash their radio chassis in the dishwasher! After that bad socket incident, I just go over the chassis with a damp cloth, I never spray the chassis with anything unless it is in really bad shape.

The only thing it could have been was a left over spot of Naval Jelly. Of course, I did have to wash that off but I tried to be careful.... Oh well. What about denatured alcohol? That would clean and dry things up really fast. It would remove any Naval Jelly, oils, moisture, whatever.

This socket only has 5 holes in it not like the others with 8. I suppose it doesn't matter. I can just make sure I wire the correct ones. I'll check out Ebay or what ever. Thanks for that tip.

It looks like a phenolic wafer socket. Measure the distance between the holes used to attach it to the chassis and send me your mailing address. I'll look in my box of sockets to see if I have a match and mail it to you tomorrow if I find one.

Wow... thank you... I'll send you a PM..

Hey... I was wondering, I've removed the 5z4 socket. If I were to test the filament part of the set as FUNAI suggested, should I put in all the tubes or certain ones or one at a time.. the solid black ones as well as the vacuum ones? (Of course, there would be no 5z4)

Now that I am looking over tubes, I noticed something. We have been talking about the 5z4 socket. The tube that was in that socket is a 5Y3 GT by Raytheon. It isn't one of the substitutions listed for 5Z4 on the Nostalgia Air website. Is this the correct tube?

On the matter of testing the filament string, you could just put in one tube at a time, as this set is wired in parallel. Some cheaper sets were wired in series, which meant that just like a cheap set of christmas lights, when one bulb, or in this case, tube, goes, then the whole set would die. But in this set that is not such an issue. Also, I would like to emphasize, if you are going to try this, you must not only pull the rectifier tube, but clip all of the wires coming from the transformer leading to the 5z4 socket. Even if the tube is pulled, the socket will continue to arc, as it is faulty.

Looking at the 5z4 vs. 5y3: They pin out the same, but the 5z4 has a cathode, while the 5y3 does not. I'm not sure if this would cause a problem or not, but if I was in your position I would get a proper 5z4.

Here are the pinouts;
5z4 The cathode is attached to pin 8, along with the filament string:

http://www.nostalgiaair.org/tubes/5z4.htm

5y3 Note that the filaments do the work that the cathode was doing in the 5z4:

http://www.nostalgiaair.org/tubes/5y3.htm

I have removed the socket all together waiting for a replacement. Question... pin 1 was ground, Pin 2, 3, 4 were transformer only. Pin 8 was the transformer as well but there was a bunch of other stuff connected from there starting with a 40K resistor, then 10uF 500V electo that replaced the large one on top and to a bus of other passives. Since those extras on pin 8 are no longer connected to anything, is there a problem or a reason not to continue this test of the tubes?

Ok, I just looked at you post a little closer... sorry... since pin 8 is the filament string, I guess there is no reason to test it yet... ?

the rectifier tube is on a different filament string-a 5 volt string instead of the 6.3v that the rest of the set runs on. So make sure that transformer lead on pin 8 is pulled too.

Just double checking... Since there is no socket for the power rectifier right now and all the leads that used to be connected to it aren't connected to anything, do you mean to make sure the other components that used to be on pin 8 are separated from the transformer lead? I know I'm being kind of redundant but I could have missed something that I didn't pick up on. Thanks

Now that was fun! I just powered it up without the 5z4 socket and tried out one tube at a time, then added back each one till all tubes were in. No kaboom, no shorts, no fizzles, no cracks, no fire, arcs or smell. I then, plugged strait into the house current, no bulb tester, and the tubes just warmed up nicely with an intimate glow reminiscent of winter radio listening and a warm fireplace. I let it run for about 5 minutes and then shut it down.

So far, so good. Now if I can just get the guts to do some readings on the circuits.

I am very happy!

Thanks for standing by, guys!

Now that is great news! Keep us posted on how it goes when you get that new socket in there.

You shouldn't have any problem using a 5Y3 in place of the 5Z4. The NJ7P database (http://www.nj7p.org/Tube4.php?tube=5z4) references the characteristics of the 5Y3 for the 5Z4. I was wondering about the rectifier tube in your set. I have never seen a glass 5Z4 but I figured that I had just never come across one before.

Hey everyone. I would like to thank Sean for the wafer socket. It arrived today and of course I slapped that thing in. On that socket, the 5z4, I have 390V AC from pin 4 the chassis and 390V AC from pin 6 to chassis. I am getting 7.9V AC from 2 to 8 and 7.9V AC from 2 to 7... no tubes, no fizz, no smoke.

How's that sound?

If that's OK, should I just plug it all together with the speaker and see what happens or are there other checks to do?

I'm excited!

You might plug it into your light bulb tester just for a quick check but otherwise you should be good to plug the tubes in and fire it up. The voltages will be a little higher than shown on the schematic since those windings are not being loaded down by the tubes.

Ok, here's my story...

I plugged everything in including the 5y3 (aka 5z4) and the speaker. I powered up and heard some speaker static and a hum. My bulb tester went up, and I turned it all off. I pulled the 5z4 and the speaker because I knew everything else had seemed to be OK before. I turned my bulb tester back on and it looked like the radio switch was on. When I turned the radio switch off, it was off. Whether the switch was on or off the radio was still on. I pulled everything and I removed the on/off/tone switch which was one of the things I didn't fool with during the cleaning. When I opened it up, it was full of all kinds of old oils, dirt and whatnot; it was a mess. Some of the wires were loose or broken, but anyway, I took it all apart, dumped it all in denatured alcohol for a while, cleaned it and put on some nice new wires. I put it all back together again including the speaker and the short was gone; the switch worked very well. But now, no sound. I don't see any radiation coming from the 5z4 though there is a little heat at touch but not much. I took out the 5z4 and removed the speaker and everything is the way it was yesterday with nice glows from the tubes and no shorts showing on the bulb.

Can any of you make anything out of this or give me a little direction? I'm kind of stumped again.

Thanks!!!

The 5Y3 should have 5 volts across it's filament (pins 2 & 8). Have you tried measuring that ?

Yep.. back at post 60 I wrote down the 4 points. It is sowing 7.9V.

So you did. Is that with the 5Y3 installed? If so, that's pretty high and you should check your tube for filament continuity.

The rectifier filaments may read high until you have a current draw going. The power supply for my GE 802 was the same-I was getting 8 volts at idle on the filament string, and then back to 5v when it was running the set.

Tell us the plate voltage of say, pin 3 on the 6f6. It should be at least a couple hundred volts. Tell us if you have any voltage on c14 (your 10 mfd electrolytic capacitor) on the positive end of the cap versus the chassis. If you are getting voltage at that lytic but not at the 6f6, then you may have a problem with the field coil in your speaker.

Well, things are way off then. With the tube in I am getting 20mV on pin 3 and 7.4V on pin 2 . I am getting a couple of mV on the + side of the 10uF 25V cap.

oops

I just checked continuity of the pins on the 6F6 tube. The only continuity I get is between 2 and 7. Nothing else. I don't know if that's good or bad.

Well, things are way off then. With the tube in I am getting 20mV on pin 3 and 7.4V on pin 2 . I am getting a couple of mV on the + side of the 10uF 25V cap.

oops

Those are the filament pins on the 6F6 so that's OK. I hope you meant to say 10uF 400V cap not 25V. That's what the schematic specifies for C-14.

There's a 10uF 25V at C-31 which was in a dry electro pack together with a 4uf 450V. I guess you meant one of the big caps on the top. On this model (A66) it was an 8uf 500V. I replaced that with a 10uF 500V electro. That voltage reads non existent.

You know, I'm going to take a step back and do some checking. The learning curve has been a big one in the last couple of days. I'm just wondering if I should make sure there aren't mistakes that I wouldn't have noticed last week that I would notice now. You never know.

When you measured the voltage on C14 were you trying to measure it as AC or DC? The filament voltages and the voltages on the plates (pins 4 & 6) of the 5Z5 (5Y3) will all be AC. Everything else is DC.

I hope I don't sound condescending when I ask you questions like this because that is not my intention. I don't know what your experience is with working on electronics so that is why I am asking about how you are taking your measurements. I used to work in field service for my employer and did a lot of troubleshooting over the phone with people who did not know how to use a multimeter. I used to have to tell people to put the switch on their meter to the horseshoe for taking resistance measurements.

Ha... yeah, It's OK. I have no problem being reminded about the most menial things. I have many time had the wrong meter setting just out of forgetfulness. My computer electronics is very good. My PCB work is fair. My radio and general electronics knowhow is well into the learning process but a long way to go. The old stuff is so different than anything I have had to troubleshoot. Just say what is direct and I can put it to use. No worry. It is actually appreciated.

Martin

I used to work in field service for my employer and did a lot of troubleshooting over the phone with people who did not know how to use a multimeter. I used to have to tell people to put the switch on their meter to the horseshoe for taking resistance measurements.

Reminds me of my days working in internet tech support telling people to click their mouse twice really really fast on the big blue E. LOL btw, I like your avitar - brings back memories!

Well, in stating the obvious, something is killing your B+. I would next suggest that you disconnect everything from the rectifier socket that does not come from the transformer, power the radio up, and see what you have. If your voltage is back up, then you have issues further down the line. If your voltage is still flatlined, then there is something wrong with that 5y3, or the way you wired in the new socket. Whatever it is, we're getting to it.

Hey, I'm back.

I clipped the only thing that is not transformer from the 5y3 socket and the 5y3 is removed. I did leave the ground on pin 1 though???? I have full power (370V AC) from pins 4 and 6 to chassis and 5.5V between pins 2 and 8. I'm guessing the reason the voltage went down from 7.9 to 5.5 is that I have the other tubes and the lights connected now. Last time none of them were in. There is 0V on 2 and 8 to chassis.

I have a confusion question... How do I check the polarity of the circuit where the 10uF 500V electro is? When I put the cap in, I was just following what I thought was the correct position based on the old cap. The old wiring was too discolored to make out. I don't want this thing exploding in my face when we do figure out what the power problem is with the 5y3.

Thanks!

Do you mean C14? The negative will go to the chassis. The positive connects to pin 8 of the 5Z4 (5Y3) according to the wiring layout. The negative leads of all of the electrolytic capacitors in this set are connected to the chassis (C13, C14, C31, C32, C33, C36, C37).

You will have to fill me in here. The original wiring (and what I can decipher on this rather illegible schematic) goes from 5y3 pin 8 to the 10uF 500V to the speaker. Now, all the caps on the other side of the radio are connected directly to ground. The multi dry cap packs (replaced with ECs) go to ground. The 16uF goes all over the place with a lot of smaller caps a VR... I usually get replacement right, but I'll have to say I could have been asleep or something.

Comment away!

OMG... Are those 2 caps, 10uF and 16uF, grounded by their old mounting? If so... There is a problem! They are not on their mounting anymore. They are just clipped off and the new caps are underneath... wired incorrectly!

OMG... Are those 2 caps, 10uF and 16uF, grounded by their old mounting? If so... There is a problem! They are not on their mounting anymore. They are just clipped off and the new caps are underneath... wired incorrectly!

Yes, most likely they were. How did you wire the new caps ? Like sean said, the negative goes to the chassis.

Got it! I just rewired. It seems a lot more logical that's for sure. I looked closer at the old cap mounting and saw a rubber insulator separating the center of the cap from the screw in mounting and got the message. A little late but at least I know how those things work now... and don't work as well. I don't see all that well and thought the 2 solder points on the base were separate pins, so I just tried to figure which was was + and which was -. That was stupid. Everything was split and going nowhere!

I am going to take a break before I look things over and fire it up again.

Well, that was interesting but no cupie doll. I have 4V on pin 2 to ground now on the 5y3 w/o tube and 6f6 with tube. With both those tubes in and the speaker plugged in, I still show a short on the bulb tester but not as sharp as before; it's still too high though. Without tubes, all the main voltages have reasonable readings as before. I still show no voltage on the + side of the 10uF 500V cap (which in now neg. to chassis).

Heeelllp! I'm not sure what to check next.

If my schematic was clearer, I think it would help. Are there other sources for those manuals? This is just such low res that even panning in, the words and numbers are a complete blur. Since I don't know enough about electronics, it's all guessing for me trying to figure it out.

You guys have been great and very patient. Thanks.

I scanned the Rider information that should be better than what is on Nostalgia Air. Shoot me an email and I'll email it to you. seanbart at fidnet dot com.

You probably didn't do it but you want to make sure that the old electrolytic can capacitors are not connected to the circuit. Don't use the original positive connection on the can as a tie point to connect the positive of the new capacitor. Leaving the negative side of the old cap connected is fine just as long as the positive is not connected also.

Yup. The old caps are fully dysfunctional! They still look nice on top though. And thanks for the offer!

Without the 5y3 tube in place, measuring from either pins 2 or 8 to ground will give you a skewed result. Put the meter lead on BOTH pins 2 and 8 to measure ac voltage across them. It should be 5v-8v. Now, with the 5y3 pulled, also measure from pin 4 to ground and pin 6 to ground. You should be getting some pretty high ac voltages (250v, 350v) there as well.

Yup... I wasn't thinking. I get 370VAC 4 and 6 to chassis tubes in except 5y3, and 395VAC all tubes out. I get 5.5VAC between pins 2 and 8 when all but the 5y3 are in and 7.4VAC when all tubes are missing.

How does one check the speaker transformer? I get an arbitrary 1.281 ohms on 2 of the speaker connections... probably a 1 ohm speaker. I'd better not put it on my stereo lest I blow out my output transistors.

For speaker transformer, do you mean the field coil, or the audio output transformer? The speaker itself should have 3 or four connections (it depends on if the field and voice coils share a ground connection). The field coil should have about 1330 ohms across it, according to the schematic, while the voice coil of the speaker should be something like 5-6 ohms (it has a hum-reducing coil in series with it).

These old speakers use the field coil as an electromagnet, as well as a filter in the power supply for the whole radio. Hence, if the speaker is disconnected, it will kill the power to the whole radio.

If a field coil speaker is dead, fret not, modern speakers can be used. Simply hooking up a modern 8 ohm speaker to the radio's old voice coil connections will get you started, and to make up for the missing field coil, put a fat 10w resistor of 1300 ohms value or so across those old field coil leads to replace it. This isn't to say that your speaker is necessarily bad; but I figured I would cover the wonderful world of electrodynamic speakers while we were on the subject.

....Although now looking at your readings, it looks like your rectifier tube may be working, and the next thing down the line that would kill your radio's B+ would be your speaker-isn't this fun?

For me... it's as fun as it gets. Many call me boring though.

I'm going to come back to your speaker discussion in a moment but I have been doing some snooping. I have tried to follow as many circuit connections as possible and following the schematic as much as I can decipher it. I started backward from the speaker connection (3 of them to the radio) following the path through the caps, power, switch eventually terminating my adventure at the 6f6 and the 5y3. everything was connected correctly, polarity on caps correct, I even checked all the solder joints and did a continuity check on all the connections therewith. I can't see anything wrong. So, I plugged it all back together and raised my light bulb to 75W. As it should, the bulb went up while things charged and then backed down again though not as much as I would expect. The tubes started to glow and after about 30 or so seconds, I heard a little noise in the speaker. Not much. Well, WTH... I put in a 150W bulb and the same thing but the tubes were brighter. The bulb started up slow and stayed there then went up to about 20% at which point I heard more noise in the speaker. Not a loud hum or a lot of static or Inagodadavida or anything, just that radio noise when there is no station and your between bands of something. So, I said... let's burn the house down! I plugged into the house current.... and the house didn't burn down.. neither did the radio. It just warmed up for a few seconds, the tubes were nice and bright and the speaker was the same as before. 'no noticeable electrical odor, no exploding caps. Upon adjusting the tuner, I got nothing, but then I don't have an antenna wire hooked up either. I figure, when it's time to think about tuning I'll think about an antenna.

OK... what have I got guys?

Speakers... There are 3 wires from the radio to 3 of 5 pins at the plug. The plug on the speaker side interestingly is connected directly to the voice coil! Hmm, never saw that before. There is a transformer of sorts that is screwed right to the back side of the speaker frame. That's the one I was talking about. The main speaker coil is not in question.. yet. BTW, I just built a set of 8 Ohm speakers for my stereo amp with homemade 2 way crossovers made on a PCB that I drew then etched with peroxide and toilet bowl cleaner. They are working really well.

But, I still don't know much about antique radio, that's for sure!

Does it look something like this ? This one has two wires going to the field coil and two to the audio output transformer bolted to the back.

Looks like yours has a common connection between one end of the field coil and the audio output transformer so only 3 wires are needed.

It looks similar but comparing the plug size to the overall size, it looks as if mine is much larger. Mine is about 10" across. Mine also has an actual transformer bolted to it on the side like where those sets of 2 holes are in your picture and completely separate from the magnet coil in the middle. The male plug has 5 pins and an extra space. The female side has 5 holes but only 3 have actual contacts in them that are wired back to the radio.

OK, how about this then ? They all work the same way regardless of the physical position of the transformer. Any chance you could takes some pics so we can see what's going on ?

Anyhoo - if you can determine which of those 3 wires is common to the field coil and transformer, you should have about 1330 ohms between that and one wire (field coil) and 712 ohms on the other (audio transformer). Make sure the set is off and the caps are discharged before you check that. Now that you've got it powering up, there could be 100s of volts across those caps.

Speaking of that, have you tried measuring the voltage going to that speaker's field coil or across the 10MFD cap ?

Hmmm...if you're getting some white noise static across that speaker, then maybe your B+ is fine. Just power up the radio, and put your finger on the antenna terminal (to be safe, don't grab the chassis at the same time). With your finger on the terminal, the static should get louder, and instantly much more quieter when you remove your finger.

Do a little am radio research for your area. If you don't know what your local stations are, then grab the cheapest radio you have and see what you pick up strongly. You should be able to easily pick them up on your GE with your "finger antenna". If you should tire of making yourself the antenna, just use several feet of any old hookup wire you have laying around.

Oh, that it would be so easy....

not a thing... :tears:

Ya know, it's not really white noise either. it's just a faint hum an a cracking or 2 when I move the knobs. The background noise does rise when I turn up the tone control or the volume. I don't hear any sound changes when I change from one band to another either.

Wishful thinking before... now back to the grind stone.

Touch your soldering iron to the center terminal on the volume control while the radio is power up...does it produce a hum?

Alternately, you could put your finger on the cap of the 6j7 tube and do the same thing.

Thank you very much Sean for the much improved version of the schematic!

First thing I see on it that's different than I could make out is R-17 that is not listed on the parts list but on the schematic is says 300K ohms. I thought it said 500K ohms on the old schematic therefore I put in 500K ohms.

It's across a couple of pins on the angular connecting bar (I have no idea what you call it) near the C-33 cap. Does this make a big difference? If it does, I had better replace it.

Funai, we cross posted... I'll try it.

Wow... more excitement. Yes there is a slight increase in hum when I put my finger on the cap of the 6j7.

And... there is a very small intermittent arc on pin 2 and/or 3 under the 6f6 socket when I increase the tone control knob (on/off switch as well)

So many things to do. Life is good.

Tell us more about this arc on the 6f6-this concerns me a bit.

Moving on, your finger test on the 6j7 cap tells us that your amp is working just fine. You should be able to adjust the tone control and volume control and alter the sound of the hum your finger is producing. If you can do that, then all is basically well with the amp section.

This is a similar arc that I had with the 5y3 socket recently. It's seems to be coming from between the 2 layers of the wafer. It is not arcing from the pin of the tube itself. It is between the pin holder on the socket and the wafer. It passes sporadically sometimes at pin 2 and sometimes pin 3 and sometimes not at all. If I adjust the tone control upward it increases he incidence. It's probably more of that oily stuff that has made its way between the wafers. I think I will just try replacing it like the other. But if you have any ideas what it may be that is different, please let me know. I can always check that before or while I'm replacing the wafer.

The arcing might be because of naval jelly getting in there, or some other chemical. Wafer sockets are prone to breaking down nastily in there where you can't see anything going on. Once it starts it makes a carbon track so it self perpetuates. Only cure is cleaning and grinding it out or replacement.

Thanks Reece! How do you grind it out? The arc is between the wafer layers. 'just take the rivets out, clean/grind the 2 parts and replace the rivets?

Here's my nightly update...

The new wafer is in. I found one at a junk store and works great. No arc. The speaker works. The volume control is working. The tone control is working. The finger on the on the 6k7 gives a sharp rise in the speaker volume. All the parts look great and no smoke/smell etc.

There are also no incoming signals detected. There are a great many AM stations around here that should come in strong.

I am now on to the next thing... hearing something radio like.

On this, I will really need some help. I hope you guys aren't too tired of me yet. I'm almost there... I hope.

Awesome :thmbsp:
I don't think anyone is tired of this thread - over 1,000 views :yes:
A great way to troubleshoot a radio once you're at this point is to work your way backwards from the speaker. You've already determined that it's OK and the audio amp is OK so keep working back towards the antenna. Check your work, the tubes, the voltages, etc. You're in the homestretch now!

That's very good! Now we'll be messing more with the radio's front end-the 6A8 and 6K7 in particular. Measure the pin voltages on all of those tubes and tell us what you get (set your meter for AC voltages for the filament tests, DC for all of the rest). We'll assume for now that it is an issue with a dead or a singular circuit error for now.

Rodger captain!

OK... I did a round of readings. To tell the truth, I'm not sure what the difference is between "filament" and "the rest". But this is what I have so far:

6A8:
pin 1 - nothing
pin 2 - nothing
pin 3 - .2 - .5 VDC
pin 4 - .01 - .02 VAC
pin 5 - 1 VAC
pin 6 - 3 VDC
pin 7 - 7.13 VAC
pin 8 - .9 VAC

6K7:
pin 1 - 0
pin 2 - 7.12 VAC
pin 3 - ?
pin 4 - 88.6 VDC
pin 5 - 3 VDC
pin 6 - n/a
pin 7 - 0
pin 8 - 3 VDC

This is with the tubes in. Should I do it without? I'd better wait till it cools down...

You should be getting something like:

6A8

Pin 1:nothing
Pin2: 6.3v AC
Pin3: about 200v DC
Pin4: at least 100v DC
Pin5: not much of anything
Pin6: probably nothing here, either
Pin7: 6.3v AC
Pin8: 4.3v DC

6k7
Pin 1: nothing
Pin2: 6.3v AC
Pin3: 250v DC
Pin4: 102v DC
Pin5: 3.4v DC
Pin6: nothing
Pin7: 6.3v AC
Pin8: 3.4v DC

These are just kinda what I threw together looking at the tube datasheets and a similar schematic. I'm probably pretty wrong with the 6A8, but there should at least be high voltage on pin 3. Basically, those high voltages are the ones you will need. To properly measure the filaments, set your meter to AC volts, and put your meter leads on pins 2 and 7 of those tubes.

Next time you make measurements, pull the 6A8 and 6K7 tubes and see if the B+ voltages come up. I've had radios with bad tubes that would drag B+ down. I see that the 6k7 tube is getting some voltage on pin 4, with 88v. Since that 88v comes off the line from the power to the 6k7's plate, you should be getting something on pin 3 as well.

I have 7.2 VAC between pin 2 and 7 on both tube sockets (no tubes)

6K7 has 284 VDC on pin 3 with the tube.
6A8 has 280 VDC on pin 3 with the tube.

I didn't have my meter set high enough before.

I forgot to mention pin 8:

6K7 - 3 VDC
6A8 - 4.7 VDC

From the schematic here is what you should have on the 6A8 and 6K7:

6A8
Pin 1 0V
Pin 2 to Pin 7 6.3VAC
Pin 3 262VDC
Pin 4 102VDC
Pin 5 Not shown but should be negative DC
Pin 6 190VDC
Pin 8 4.3VDC

6K7
Pin 1 0V
Pin 2 to Pin 7 6.3VAC
Pin 3 251VDC
Pin 4 102VDC
Pin 5 3.4VDC
Pin 6 not used
Pin 8 3.4VDC

Pretty close to what Leadlike came up with. The voltages you got on pin 3 of the 6K7 and 6A8 are somewhat in line with what you should get. The voltages on pin 8 of both tubes are good. What you show on pin 6 of the 6A8 in post #107 is way low. Measure the voltage you have on capacitor C13 (junction of C13 and 40,000ohm R3). If this voltage is really low then either there is a short around there or R3 is open. If this voltage is high (around 390V) then you probably have an open winding on the oscillator coil L5 and/or L7.

That pin leads to the switch that changes bands. I don't see any visible short... But... the wires leading to the OSC Conv. are the only wires that I did not replace on the radio. I didn't want to disturb those coils and they looked fair. Maybe they are bad. Most of the wires in this radio had the insulation crumbling off, some bare. I think the simple thing to do first is to replace those wires and check the connections on the switch while I do it.

Bingo... Sean. The 40K was soldered one spot off on the way to C13. Now it shows 111V at pin 6 and at C13. No magic voices though.

I just let it warm up for about 5 minutes and turned the tone all the way up. I was able to hear 1 station distantly on AM. But I have to turn up the volume about half way and the hum on the speaker is pretty loud. I can tell, this radio could get quite loud when turned up.

It's starting to happen.....

Have you tried adding an antenna yet?

Thanks for putting up the proper voltages, Sean, I'm pretty happy I only made one major mistake...

Yup.. 1 original 8 foot long stranded copper wire with that cloth insulation it came with.

Pin 4 on the 6K7 is low. It is tied directly to pin 5 of the 6A8 and they should both have 102VDC. These points get fed from the B+ through the 8800 ohm resistor R9. R7 and R8 along with R9 create a voltage divider to supply screen voltages for the 6A8, 6K7, and 6J7.

When you get the voltages within reason maybe you can tweak the I.F. transformer adjustments to see if that helps. It is best to have a signal generator for this but you can get close enough by tuning in a station and then slowly adjusting the screws that appear to be on the bottoms of the transformers. I would suggest going in the order of C27, C24, C19, C17 as shown on the underside view in the service info. You would adjust each for maximum signal.

Are you sure it's pin 4 on the 6K7 to pin 5 on the 6A8? I can change it but it's pin 4 to pin 4 now and maybe my eyes are playing tricks, but I think the schematic says 4 to 4 to R9. You are the boss though... just checking.

Just checked... there is 101 VDC on pin 4 of the 6K7 and pin 4 of the 6A8. Is that right... or wrong pin?

looks like pin 4 to pin 4 to me, too-I'm using the Nostalgia Air schematic of the A64, which NA claims is the same as your A66.

http://www.nostalgiaair.org/PagesByModel/754/M0007754.pdf

Either way, that 8800 ohm resistor is really the only offender that could be causing this low voltage.

Ah, you replied while I was typing. Those voltages are just fine. Your radio appears to be basically functional now. Have you hit the bandswitches and volume/tone controls with cleaner yet?

yes.. cleaned with denatured alcohol.

a question...

There's a dogbone resistor marked 50K that is across a couple of terminals inside the housing of the 1st IF. I have had to replace all but 1 of those underneath the radio as they were more than 20% over tolerance. Though measuring it without clipping it isn't the most accurate way to test it, it's showing 44K ohms which is under tolerance. If it's a 10% it's off the mark. If it's a 20% I guess it's OK. Should I replace it or leave it alone?

Thanks...

:tears:

Oh boy... I let the radio heat up for 15 minutes or so, I tuned into the only station that I could hear. Starting with C-27 on the 2nd IF I tweaked just slightly one way then another and got a little clearer reception. The went to C-24 on the same and got a slight edge there as well. Then I went to C-19 and it got quite a bit better. Then came C17 and the moment I touched the screw I heard "clap" and no more sound.. dead... empty. The tubes look OK physically, there seem to be the same voltages as before, though I didn't check them all yet. There doesn't seem to be any excessive heat and no smell. What to do???

Oh, and I was so looking forward to President Roosevelt's speech tonight.

Somehow, my radio is back and now I have 2 stations. Go figure. I noticed when I touch the top of the 6K7 the sound stops. When I touch the top of the 6J7 there is a high pitched squeal. That isn't why it stopped working before I don't think but it's an observation.

Sometimes the IF transformer adjustment screws can be "hot" and can short B+ to the can, so it's good to use a plastic alignment tool for that, RS used to sell them, still might? In lieu of that, you can wrap a piece of tape or use heat shrink tubing around a small screwdriver shaft just leaving the very tip exposed.

Did you clean the tuning capacitor? Be careful not to get this on the trimmer caps with their mica insulators on the side of the tuning capacitor, as the mica can be damaged. Blast in between the tuning plates with computer keyboard cleaning "air" or with CRC Electronic Cleaner, available at auto parts stores, leaves no residue. Inspect, be sure none of the rotor plates are touching the stator plates. Clean out the ball bearings with a solvent and regrease with a little light grease like white lithium. One drop of light oil from a toothpick on the other cap bearings.

Check to see if your local oscillator is working. Place another functioning AM radio tuned to an unused frequency about 1500 Khz right next to your GE. Turn the GE on and tune it around between 900 to 1200. At some point there should be a squeal or a "rush" from the other radio indicating your GE's local oscillator is working. This signal will come in at the GE dial setting plus the 465 Khz I.F. frequency, so 1000 on the GE should come in at 1465 on the other radio.

Great info... Thanks for the tips... back to radio land. Someone at the electronics store said he used denatured alcohol to clean the tuning cap then compressed air. I have stayed away from it so far just to be careful.

Martin

I get a squeal with the GE at 1060 khz and the other radio at about 1500.

That's great! It means your local oscillator is working so that it can mix with the received signal to produce the I.F. frequency. I wasn't sure before if you were just receiving an RF signal blasting through or if the superhetrodyne circuits were working.

What I like to do is make a copy of the schematic and then go over the chassis wire by wire and mark them off one by one on the schematic with a highlighter as I go. Concentrate now on the circuits around the 6A8 and the 6K7. Something keeping the signal from getting strongly through the IF section? You mention a 50K resistor inside an IF can: I don't see it; can you I.D. it on the schematic? Does it look factory? Sometimes resistors are used to lessen selectivity but ...?

Do the easy stuff first! Clean the cap!

It looks like all the other dogbone type that were underneath. I don't see it on the schematic. It's green w/ a black end and an orange dot... I guess 1/4 W. It looks factory. When I tap the top of the 6K7 once, there in a quick squeal then the reception gets way better for a minute or so. The volume increases by 2 x and the hum is less noticeable. Does that conjure up any possibilities?

Did you clean the tube pins and sockets? This sounds like intermittent connections. If you have some electronic cleaner, put some in a bottle cap and use a cotton swab to put some on the pins of one tube, then plug the tube in and out of its socket several times. If no cleaner, use WD-40. Do all the tubes, including the top caps. See if that helps.

The tube pins are clean. Cleaning the sockets is a conundrum. I lost 2 sockets so far probably because of naval jelly seepage causing an arc between the wafers. Personally, I think WD-40 could very possibly do the same thing. I have deoxit but the same applies. Denatured alcohol is the only thing I can think of that would have absolutely no residual effects. Even compressed air can leave a water residue if it gets in a closed space and doesn't dissipate fast enough. This is my experience with mother boards and computer components.

If I could just get something small enough that I could put a thin cotton cloth over like a handkerchief, dip it in the alcohol and put it through, It would seem to me safest. Hey, don't listen to me. I'm a rookie.

I did all the cleaning you suggested earlier. Thanks.

Plugging the wetted tube pins in and out of the sockets won't wet the sockets. The pins will get a little of the cleaner juice on the socket contacts and improve things. I've never had any problem this way. Any socket problem from before is probably from the naval jelly, which is corrosive stuff. If you're antsy about it, just wiggle the tubes and the ones that give a crackle, plug the dry tubes in and out several times. Look underneath and see if the pins make good contact with the socket terminals. Always a possibility on 74 year old stuff! Anything iffy you can always bend a little bit.

In the underchassis picture: the square brown cap with six dots on it: can't tell from the picture. What is the mfrs. name on the cap? When reading the mfr's name on the cap right side up, which dot is in the upper left hand corner? What two points in the circuit does the cap connect to? Have you identified it on the schematic as cap no. XX ?

It's a Cornell-Dubilier. The name reads twice in both directions so the name is always up. If you read the usa written to the left in the upright position, the upper left dot is blue. There are several of those type under there. I haven't replaced them.

Reese... (and everyone else for that matter) the radio sockets and tube pins are pretty clean and the connectors tight. The squeal I am talking about has to do with just coming in contact with the top of the 6K7. It's not the tap itself. I said tap to illustrate the amount of time I am in contact with it. If I put my finger on it and hold it there the squeal is painfully loud. It's a really high pitched squeak, squeal, electrical... yikes, it's loud. But everything is improved after I do that. When the machine gets really warm, it "seems" to hold more stable. It's hard to tell. I am actually beginning to hear transmissions on the SW bands. I can't make anything out but their are voices.

This is pretty fun.

Where are the two wires from this cap connected in the circuit?

It goes from ground to the OCS at what looks like L8. It's one of the terminals of the oscillator. Looks like C11.

I have been giving the wrong information about the squeal sound...

I have been repeating 6K7....

It's the 6J7 that makes the noise and increases the reception... the amp tube

Sorry...

Wonder if one of the tubes is oscillating, or if RF is getting into the 6K7. Then when you upset the apple cart by touching the top cap it stops for a while. Did you replace the IF cans to operate the radio? They're needed for shielding. That 50K resistor inside the IF can could be reading off due to being in circuit? Might lift one end and check. I might try bridging small micas in the detector/1st audio area with another small mica, see if there's an improvement.

Some other ideas out there? :saywhat:

Great... I'll give these a try! I just read yesterday that this fading out can be a bad cap or a weak tube. All caps except the micas have been replaced. What do you think? Yes, the cans are in place.

Here's another little tidbit. There is supposed to be a 1M ohm resistor from ground to the intersection of the wire to 6J7 and another to a cap that leads to the volume control. With the resistor in place there is no reaction from the 6J7 and no hum but the sound volume is almost nonexistent with the volume turned full blast. I have tried lower resistance 500K, 220K, 100K, 50K, 20K... the sound gets more distant till it totally disappears. If I remove resistance completely, the hum resumes but I have all the volume I can handle.

Can someone tell me what's happening here?

Thanks!!!

I followed the suggestion that Tubology so graciously offered about following the circuit and checking off as I go. Well, there ya go... I found one more stupid mistake. A .05 cap had been in the wrong place.. Voila, I have a lot more reception, less hum and less of that weird tap thing on the 6J7. It is still there but about 5 x less. Although, I still have to go without the 1M ohm resistor I mentioned last post or there is very little volume.

I'll keep going and see what I come up with. SW is a bit weak, but it's nice to have AM!

:banana::music::D

Tracking down that hum: is the resistance element in the volume control OK? With the set turned off: see the three terminals that are together: clip your ohmmeter to the two outer ones. Should get around 250K. Then clip to center and one outer, by turning the control shaft should be able to vary from 250K to practically zero. Center and other outer, should vary the same but in reverse.

Is the low side terminal of the volume control solidly grounded? This would be the outer terminal of the three terminals together, that is the lower one on the schematic shown going to ground.

As to the rogue 1 meg resistor: try higher values and see what happens. And keep tracing that schematic when you're rested! :yes:

Now that's the strangest thing... on the volume control, outside on either side to the middle, the resistance goes from 0 ohms to about 260K ohms... at half way! continuing, it starts down again and at full volume ends at 100K ohms. From side to side I only get 88K. :scratch2: But the volume does work...

Oh.......... scrap all that. This is an edit.

I just removed the volume control completely to get a better reading. It's 0 to 254K ohms on one side, then 0 to 355K ohms at 3/4 way then goes back down to 254K.

Side to side it's 254K.

I'm almost there, Guys. I just found an old antique collector in town with
some old tubes. One of them was a 6J7 G so I though why not. I gave him a dollar and took it to a place with a tester. It tested as high as it can get. I stuck it in and the hum is down to practically nil. The volume is not quite as high but at least there's no hum on stations and practically none in between. Most of the reception issues now are just antenna related.

I would like to send out a huge thank you to all those who have guided me through this adventurous procedure. I have a lot of computer and mother board experience... but in computers, all the real important stuff is already laid out and you just have to know your passives and hardware. Working on this antique radio has sure showed me how much I don't know about what is at work in electronics. I would bet that more than 75% of computer "experts" are just "package" experts, E.G. tear open the plastic bag, stick the part in the little holes in the traces and solder it in. Even when you are working with PCB, you lay it all out before hand and the traces are perfect (hopefully), then you don't think about that anymore and stick in the parts. Big deal. But with radio.... the wires, the connections, the modifications, the common sense, the rudimentary circuitry, 3 dimensional space instead of 2... It makes one think in a whole different way, a more thorough way.

I think the only thing left to do is to try adjusting the SW side. Is there a general procedure that can get me pretty close. I don't have a scope or anything but reading the manual there are tools mentioned that I'm not sure I understand how to use or make like the metal filing thing or the ring. It would be really interesting to try to tune this up the old way, the way it was done back in the 30's.

Guidance offered would be greatly appreciated! :yes:

Thanks again,

Martin

That sounds wonderful! I wouldn't mess too much with the shortwave (or really any of the other radio settings) until you find a signal generator. If you are receiving any SW stations, you'll find your radio can be extremely fussy about tuning them in-so if you find yourself just wiggling the tuner back and forth with just the smallest of movements, well, that's how it is for all of these sets (and that is why we have a fine tuning knob on nicer sets).

You should be able to pick up any old signal generator for next to nothing. Even the most basic ones will have the features you need. Maybe even a member here might have one they would give away. I only just threw away two working ones this past January.

EDIT: I was working on this post for a while and when I posted it I see Leadlike had posted: he's right about using a signal generator to get it right, but if you want, and are careful, you can get good results by ear.

****

Hooray! :banana: You basically tracked it down yourself. Your radio shouldn't need heavy alignment since it works pretty well now. I am going to bet that you won't need to turn any screw but just a few degrees in either direction: resist that, please. You can do it the way old timers did/do it, without any test equipment, and have it pretty close to perfection with a screwdriver....:) You should really use a plastic screwdriver alignment tool but will be OK if you insulate the tip of a small screwdriver.

Have your ten to twenty feet or so of antenna connected. Warm up set for 20 minutes or so. Be sure the dial pointer is correct in its travel per page 6 of the NostalgiaAir (N/A)instructions for the A-64.

Always use weak stations for alignment. This avoids having the automatic volume control (AVC) acting which can confuse hearing when the signal peaks. Set your volume for a normal listening level.

High end of broadcast band: Tune to a weak station around 1500 to 1600. You must know the actual frequency of that station. You may have to listen for it to be announced if you don't know it.

Look at N/A Fig. 4 to identify locations of adjustments. If the dial pointer is not on the exact stated frequency of the station you are hearing, carefully adjust the broadcast oscillator screw just a little left or right to shift the station on the dial, following it either up or down the dial as required with the main tuning knob. Then adjust the broadcast R.F. coil trimmer for max output.

Low end of broadcast band: Tune in a weak station around 550 to 650. "Rock" the tuning dial back and forth across this station while slightly adjusting the padding capacitor next to the oscillator coil for loudest signal. The dial pointer may not line up exactly with the stated frequency of the station at the low end of the dial but that's the nature of the beast.

Intermediate Frequency : Tune in a weak signal around 1500. Locate the I.F. transformer adjustments per Fig. 4. Peak for loudest signal in this order:
Second I.F. Secondary
Second I.F. Primary
First I.F. Secondary
First I.F. Primary
Then repeat in same order.

Short wave: The National Bureau of Standards has a time signal station that broadcasts exactly on 10 and 15 megacycles (or megahertz), among other frequencies. If you are not familiar with what this sounds like, listen to this demo: it's like a clock ticking over a continuous tone, interrupted by time announcements. Open and click on "Hear Signal."

http://tf.nist.gov/stations/wwv.html

Tune the radio around 15 Mc. to see if you can hear this signal. It will be stronger during the day. You might need to add a longer antenna. The station is also on 10 Mc. but is stronger there during evening hours. It would be better to align at the 15 Mc. signal if you can. Check to see if the pointer corresponds fairly closely to the dial number. You can "walk" the dial pointer up or down by adjusting the SW oscillator trimmer. SW fades in and out a lot so don't let that fool you when peaking the trimmer. Then adjust the SW R.F. coil trimmer for max output.

Oughta do it! :music:

EDIT: Looking at the N/A entry again, I see that G.E. calls what is usually called the "antenna coil" the "R.F. Coil" (Radio Frequency.) Accordingly, I changed the references above to R.F. Coil.

You guys are great. Thanks for the info!

a couple of tweak questions:

When turning the First I.F. Secondary,I think that's L-19, I noticed it is turned as far clockwise as it can go. I can't find the center point since counterclockwise is only to lessen the reception. All the other I.F. adjustments have a clear center point. Could there be a weak component that keeps it from setting farther clockwise?

To clarify, I'm not convinced it's the volume pot necessarily.

The other is, Could the not quite right volume potentiometer cause the sound to be gruff? It works OK but the sound is gravelly especially when turned higher than 1/3.

Thank you.

Sounds like something has drifted in the first I.F. Easiest would be to parallel a small mica cap, maybe 10 to 20 pf? across that trimmer C19. Just tack one in to test. This would increase the total capacity. Since the capacity would now be too much, it should allow you to back the screw off to lower the capacity to find the peak.

Rough sound: is the speaker voice coil rubbing on the pole piece? Sometimes this is only apparent with higher volume. With the set off, with fingers of both hands carefully move the cone back and forth to check for rubbing. Jump a PM (permanent magnet) speaker across the voice coil terminals of the original speaker to see if there's a difference in sound.

Do you still have excess hum? You could set the speaker over a hole cut in a cardboard box for a baffle to hear the hum better. If there is hum, does it follow the volume control setting? If the control works smoothly with no jumps, don't think the control is the problem.

Thanks for the tip on the I.F. I'll get on it.

The gruff sound I will also check. It's hard to tell but it may disappear at very very low volume, like less than 10% volume. It seems to clear up for a moment or so though when I do that tap thing on the 6J7. That is why I think it is in the radio somewhere. It also reduces a bit after the radio has been on for 30 or 40 minutes.

I just looked at the speaker and I don't feel anything rubbing or see any tearing. But I did notice that the hum is 2 fold; there is a hum that follows the volume control and another that does not. The hum that follows the volume sounds like the kind of sound you get when you drive too close to a power line except there aren't any motors, florescent lights or power cords or line in the way. The one at the speaker is always humming and at the same volume whether the pot is up or off.

Thanks Reece.

Sometimes hum is due to heater-to-cathode partial short in the output tube. Usually that gets worse when it heats up rather than better. Maybe try a new tube. There will usually be a little hum with your ear right at the speaker but should not be objectionable at normal listening levels.

Is any of the hum tunable, that is, more when you're on a station than when in between stations? That volume controllable hum may be from electrical interference. Light dimmers, dusk to dawn lights, garage door openers, computer power supplies, almost any plug-in wall charger, can produce nasty stuff. You can put a portable radio in between stations and probe around your house and yard to sniff out sources. Even your neighbors' devices can cause this. Sometimes a different location for the radio helps, or a "real" outdoor antenna.

Ok... snooping here... I found that if I touch the uninsulated wire that goes from the R.F. broadcast coil to a Bus switch to the braid of the trimmer to the top connection of the 6A8 tube... all problems cease. The reception is 100% improved, the volume comes up which means I can turn it down and all gravel is non existent. I can touch either side of that switch and it does the same. This only happens when I touch it. If I put a wire between... no change. If I put a resistor between... no change. If I am holding a wire and touch it it fixes the problem... point, it only happens when my person is in contact. not ground, not antenna... just me. I guess the 6A8 likes me.

Not sure I'm following because I don't see any braid specifically on the schematic, and don't think the wire to the top cap is shielded (which would be a type of braid), BUT: try connecting a ground wire to the G terminal. If you don't have a dedicated ground temporarily connect it to the center screw of an outlet cover.

Edit: found the braid etc. on the pictorial

Thanks!

Stupid question... what's a G terminal?

I think you mean a ground on the radio chassis. Anyway, the upper frequencies improve greatly. I completely loose the low ones when I do that grounding. :scratch2:

This radio is just being difficult, isn't it? With the ground, what happens with the hum or roughness?

Both disappear in the upper frequencies, but the lower frequencies also disappear. I have to turn down the volume on the higher frequencies but I have to turn it to maximum to even hear the lower ones in the distance. Without the grounding, both ends are even but the volume must be turned up. Then I have a rough sound which touching the 6J7 fixes for a moment. Touching the 6A8 or those mentioned places underneath fixes everything throughout the AM freq.

Make any sense?

On the thought of I.F and Oscillator adjustment, You know I cannot tune in the Bureau of Standards time signal on either of those frequencies or anywhere near them using my digital SW receiver on which I get a lot of things. I have never been able to pull that in. If I can't get it on my digital, I surely can't rely on it for the GE radio.

Also, If anyone has a schematic for making a test oscillator, I'm sure I can throw one together.

Thanks!

If you can find a suitable station near 15 Mhz on your digital, note the frequency displayed and just shoot for that to align the G.E.

As to the strange R.F. behavior of this set: I wonder if an RF/Antenna coil is open or shorted. The fact that the trimmer is all the way tight and won't peak could also point to this. An open antenna coil can cause a hum and poor tuning. They are often fine wire and over the years corrode or snap at the terminal. See L1 through L4 on the diagram. Their approximate resistances are shown, are they close to that?

Here's L-1 through L-4 respectively: 29.5, 8.2, 2.9 and .55

L-4 seems like the only one that is a bit off. It should be more like .015

The scheme says respectively: 29, 8, 2.5, and .015

Well... I think I figured it out, although I don't really know exactly why what I did worked.

It seems to have been an antenna issue. I added a wire between the antenna terminal on the inside to the center pin on the bus that controls where the antenna is connected. That center pin is the braided wire that leads to the tuning cap on top on the side that is NOT connected to the 6A8 tube. All the unevenness between the ends on the bands and the volume issue as well as the gravelly sound are no more. I have too many channels now. They are everywhere. On the SW side, everything is clearer but if I add a ground from the chassis to the radiator in our house, I can hear Voice of China if there is such a thing... It's amazing! I have to remove the ground though if I use the AM band or I loose my lower half of the radio channels.

Now, just because it works, doesn't mean it right. If this is a bad idea, please let me know. I'm just futzing around. It would be nice to know what I did here. It's not a wire that existed before.

Thanks everyone.

Now wait a minute... it's on the schematic. But the solder terminals have never been used; they were completely clean...:scratch2::scratch2::scratch2:

:headscrat Not following exactly: can you mark up a piece of the schematic on N/A to show what you added?

hare ya go...

So you're saying that wire from the antenna terminal to the center of S1 was not there, even though shown on both the pictorial and the schematic? So any antenna you connected to the "A" terminal did nothing, until now? That's bizarre. Somebody must have taken that out in the past. There's no way that could have got out of the factory like that.....is there??? :saywhat:

I have no idea. But the spot on the S1 is clean other than the oxidation and coating stuff. Nothing has been soldered there before. It even has kind of an ornate design on it. Maybe it were meant to have the choice of using the terminal or being clipped onto by an external antenna. Maybe the original owner or seller didn't know that. Just guessing. :scratch2:

Check an original picture from the un-refurbished radio. The antenna is connected to another spot. I left that one there.

a better shot....

This has been a trip, hasn't it? :yes:

OK, what's your next project? :)

So the terminal that I have circled is the one you are saying nothing was ever connected to? Is that braid that is soldered to that terminal? If so, does it go to the tuning capacitor?

Well, first I'm going to refinish the rather ornate box it's housed in. I think it will be a very nice piece of furniture. Then I thought I would build a tube controlled proton accelerator ;) This antique radio stuff really is an interesting hobby. It is sad sometimes when I come to the end of a project like this and I just stand there looking at it and wonder what else needs to be done. I just want to keep on tweaking but there isn't anything else to do. The same thing happened after spending 2 months rebuilding my 1973 Sansui QRX-7001 which was the first time working with audio equipment. I learned so much during that period. Then afterward I didn't want to close the box. Tube radio is such a different animal that it's like a whole new technological jump. The thing is I seem to be jumping backward and it gets more interesting as I go. What would be the next thing... smoke signals?

Thanks for all the help. I hope I can come across another old radio sometime. I'll be looking I'm sure.

I'll post a picture or 2 when I dig my camera out again.

Ooops, Sean just posted. Yes, it's hooked to the tuning cap on top. What I'm talking about is the terminal (ring) just below the braid (same thing). The antenna was/is connected to the other side of that bus. To my feeble logic, It doesn't seem that it would make any difference which side it was hooked to... but it sure does. Now the antenna is hooked to both sides and works better than I thought it could.

How about a picture of the cabinet that you are going to refinish? Oh, and did the radio come with its knobs? If not, I have some GE knobs from that period that may be helpful...

Thanks! It has it's knobs. I even polished them up a bit. Pictures are coming!

Here's a couple of pix....

That is a nice little set! The cabinet is especially lovely. Were you going to do a full refinish, stripping off the old and put a new coat of lacquer on; or touch up the original?

Ooops, Sean just posted. Yes, it's hooked to the tuning cap on top. What I'm talking about is the terminal (ring) just below the braid (same thing). The antenna was/is connected to the other side of that bus. To my feeble logic, It doesn't seem that it would make any difference which side it was hooked to... but it sure does. Now the antenna is hooked to both sides and works better than I thought it could.

It seems that you bypassed the primaries of the antenna transformers (L1 & L3) and are connecting the antenna directly to the secondaries (L2 & L4). I'm not sure why it works better with the way you are connecting it but if it works it works.

Unless your cabinet looks much worse than it does in the photo I would suggest trying to restore the finish rather than strip it and refinish it. I use a mixture of 1 part boiled linseed oil, 1 part turpentine, and 1 part white vinegar to refresh old finishes. I usually apply with #0000 steel wool in the direction of the grain and then wipe it off with a clean rag. If you apply it two or three times it looks much better than just once. It will also help remove paint splatter. There are other products on the market for restoring finishes but I have not tried them. If you still don't like the way it looks after using a restoration solution then you can always strip and refinish.

Stripping is always the last possible solution for me. I hate that. Thanks for the tips. What I was planning to do was experiment with the finish and find out what it is exactly then go from there. I usually just start with a thorough cleaning. That tells me a lot about the surface. I will probably do a little hand work in the crevasses where the oils and dirt have accumulated over the years. What looks like paint is much simpler than it looks. It's candle wax that has dripped on long ago. If anything, it has preserved it. It's an easy clean. Or I could do some '70s "antiquing" where you paint it with avocado green then beat it with a chain, paint it again with another shade then use the chain again. Whoever thought up that "antiquing" process should be shot. I have seen more ruined hardwood furniture than I want to think about. No.. I'll be careful with the surface restoration and try to make it as near original as possible.

As far as the antenna, since the original connection to the terminal is from the opposite side of that bus, maybe that side has something wrong with it. It should be the same antenna source no matter which side it's connected to. But it's not. BTW, did I say that all the other strange things such as tapping the tubes and the volume changes have also disappeared since this connection? Is bypassing the primary a bad thing or less desirable? Maybe I should be looking into why it has to be connected this way.

Thanks Sean.

The only things I can think of that would cause a problem with the signal passing from the antenna through the primary and into the secondary winding are a bad or dirty connection through the band switch or bad primary windings. However your resistance measurements seem correct for these coils. I don't think GE had an issue with the antenna transformers (or coils) like Philco did but I have found fried antenna coils that had a good resistance measurement. It probably isn't worth the trouble to take the cover off of the antenna transformer to inspect the coils. Bypassing the primary could cause some issues on shortwave with the radio drifting off of a station if the antenna is moved, touched, or you come into proximity of it. I don't think it is a big deal. I like to find out why a radio does not work properly when it is wired the way it is supposed to be wired. Just my own curiosity. Please don't delve into it further just for my sake.

I have inspected the all coils pretty closely. I see no over heating, breakage, or corrosion at sight with a magnifier. I'm sure there could be things I don't readily see.

Out of curiosity, what do you do if there is a problem with a coil? What kind of fixes if any are applied to various problems?

About the only way to fix a coil is to rewind it. Sometimes if there is a break it can be repaired. If you don't see any defects with the coils then they should be fine.

Im getting here late on this. I've read the entire thread, and you have really come a long way, and gotten a really nice floor model GE out of the deal! That cabinet is really nice, and I hope that you have years of trouble free performance from it.

Bruce

Thanks Bruce. I plan to enjoy it for a long time to come, but hopefully not too trouble free. I kind of like tweaking it around a little. ;)

I think this is it. It sure is a proud thing!

And about 74 years old. Wow.

I still need to do a little with the grill cloth but I thought I would rather turn it around had have original color since it was so bleached out before. I can put up with the unevenness. I should turn it bottom up though.

Gorgeous!!! That is a radio to be proud of. What did you end up using on the cabinet? If you aren't happy with the grille cloth you might see if grillecloth.com (http://www.grillecloth.com/) has a reproduction of the original.

I love it! Very classy looking cabinet. Good work pays off....:thmbsp::yes:

Thanks for the comments. The cabinet had 3 gashes and 1 bad cigarette burn that I was a little concerned about. I thought I would have to do some wood restoration. After I did some testing around, it was clear that it was covered with about 15(?) coats of shellac so I quickly did a rub down with denatured alcohol to disrupt the surface a little then I just went through a series of sand paper routines to remove about half the surface finish. The gashes and the burn disappeared completely. So, I put 2 new coats of shellac on it and voila! I was surprised how simple that ended up being and I hardly had to disturb the original surface.

That may be a lesson to me when making furniture... many, many coats of shellac are great for preservation and restoration.

Has anyone ever tried soaking a grill cloth in something to clean or rejuvenate it?

It might shrink. Some have tried a little quick hand washing. If you can find K2R dry cleaning spray, that would be less intrusive. I haven't seen any lately but then I haven't been looking for it, either. It's a dry cleaning fluid in a spray can with fine chalk suspended in it. Shake it up, spray on, let it dry completely over half an hour or so. The fluid dissolves the dirt and the chalk absorbs it. When dry you brush off the chalk with its dirt load.

Another way might be with the cloth removed, lay it on a clean towel. Sponge on lightly upholstery cleaner foam (spray can) and immediately blot with another towel, section by section. Avoiding soaking maybe it won't shrink. All this is experimental with the particular cloth and you may end up replacing to be happier with it.