Hello everyone, today I just picked up a 1930s vintage battery operated Coronado Radio of which I don't know the model number and I'm trying to locate the service literature for it.

It is in really decent shape yet, but someone at some point in time wired a power cord up to the antenna hookup and I'm hoping no one actually attemped to plug it in that way otherwise this radio may be a shelf queen, it looks really clean underneath as well and looks like there was no servicing done to the radio (except to the battery cables and the addition of the power cord onto the antenna hookups.)

what kind of batteries were used to power this radio and does anyone have any idea which model this might be?

pictures below.

I used to have one. It wasn't a stellar performer and the cabinet was beat up so I got rid of it. I think it took 90V for the B+ supply and 1.5V for the A supply...the A supply voltage is easy to confirm by googling for the data sheet for 2-3 of the tubes and using the lowest filament voltage. (The audio outputs of battery radios often used a tube of double the A battery voltage with a center tap...the ends of the center taped filament would be jumppered together to halve the opperating voltage and double the current)

I used to have one. It wasn't a stellar performer and the cabinet was beat up so I got rid of it. I think it took 90V for the B+ supply and 1.5V for the A supply...the A supply voltage is easy to confirm by googling for the data sheet for 2-3 of the tubes and using the lowest filament voltage. (The audio outputs of battery radios often used a tube of double the A battery voltage with a center tap...the ends of the center taped filament would be jumppered together to halve the opperating voltage and double the current)

I got it mostly as a curiosity piece as I've never owned a battery powered tube radio set before, and thought it would be an interesting piece to try and fix up.

That power cord hookup to the radio's antenna terminals almost certainly would destroy the radio (not to mention possibly starting a fire) in the blink of an eye, if the plug were to be inserted into an AC outlet. Why on earth would anyone do anything like that?

Hello everyone, today I just picked up a 1930s vintage battery operated Coronado Radio of which I don't know the model number and I'm trying to locate the service literature for it.

It is in really decent shape yet, but someone at some point in time wired a power cord up to the antenna hookup and I'm hoping no one actually attemped to plug it in that way otherwise this radio may be a shelf queen, it looks really clean underneath as well and looks like there was no servicing done to the radio (except to the battery cables and the addition of the power cord onto the antenna hookups.)

what kind of batteries were used to power this radio and does anyone have any idea which model this might be?

pictures below.
It's a model 650A-B-C in Riders vol 8.
Those are 2 volt filament tubes using 90 volts B+. Chances are, the antenna coil might not be damaged, if 120 ac was applied. :scratch2:
It's easy to build a power supply because it uses only a A+ & B+ source.
Doesn't use a grid bias supply.

It's a model 650A-B-C in Riders vol 8.
Those are 2 volt filament tubes using 90 volts B+. Chances are, the antenna coil might not be damaged, if 120 ac was applied. :scratch2:
It's easy to build a power supply because it uses only a A+ & B+ source.
Doesn't use a grid bias supply.

Yeah, I checked the antenna coil and it still had continuity so I think it's fine yet. It does have AVC which is good.

That power cord hookup to the radio's antenna terminals almost certainly would destroy the radio (not to mention possibly starting a fire) in the blink of an eye, if the plug were to be inserted into an AC outlet. Why on earth would anyone do anything like that?

Yeah, I checked the antenna coil and it still had continuity so I think it's fine yet. It does have AVC which is good.

Despite Jeff's dour predictions , capacitor C1 would save the antenna coil if AC was improperly applied to the antenna terminals .

Despite Jeff's dour predictions , capacitor C1 would save the antenna coil if AC was improperly applied to the antenna terminals .

Indeed you are correct, when I tested C1 between the antenna terminal strip, and the antenna coil, C1 measured open.

I did some research and I figured out that this radio is a Coronado Model 650B which was a rebadged Arvin "Phantom" Series Farm Radio Model 628B.

I thought that was kind of interesting.

I like the cabinet!

Go to your local dollar store and get 10 9V tranaisistor radio batteries to use in series for B+, and some D cells for the filaments. The 9V batteries can be clipped together in series using their own terminals, and then the first and last ones can have wire leads with alligator clips soldered to them, which you can connect to the radio's power connector. For the A battery I'd use 2 D cells in parallel.

Before you apply power you may want to do a basic replacement of capacitors, especially any electrolytic capacitors, the AVC filter, and the audio grid coupling capacitors.

The reason these radios sound worse than normal radios, is the audio output stage is necessarily very low powered, so the speaker is designed for efficiency rather than sound quality. They can be okay though. I like yours because of the fancy grill design and late 30s deco cabinet.

I like the cabinet!

Go to your local dollar store and get 10 9V tranaisistor radio batteries to use in series for B+, and some D cells for the filaments. The 9V batteries can be clipped together in series using their own terminals, and then the first and last ones can have wire leads with alligator clips soldered to them, which you can connect to the radio's power connector. For the A battery I'd use 2 D cells in parallel.

Before you apply power you may want to do a basic replacement of capacitors, especially any electrolytic capacitors, the AVC filter, and the audio grid coupling capacitors.

The reason these radios sound worse than normal radios, is the audio output stage is necessarily very low powered, so the speaker is designed for efficiency rather than sound quality. They can be okay though. I like yours because of the fancy grill design and late 30s deco cabinet.
The radio might not work because the filament voltage should be 2 or 2.2 volts. Those tubes are probably a little tired and need the proper voltage.
I have a Coronado model 550 tombstone made by the same company, but using a single 33 tube in the audio output. It originally had a magnetic speaker that sounded lousy. I installed a PM speaker and output transformer.
Not much audio output, but doesn't sound bad. :thmbsp:

I like the cabinet!

Go to your local dollar store and get 10 9V tranaisistor radio batteries to use in series for B+, and some D cells for the filaments. The 9V batteries can be clipped together in series using their own terminals, and then the first and last ones can have wire leads with alligator clips soldered to them, which you can connect to the radio's power connector. For the A battery I'd use 2 D cells in parallel.

Before you apply power you may want to do a basic replacement of capacitors, especially any electrolytic capacitors, the AVC filter, and the audio grid coupling capacitors.

The reason these radios sound worse than normal radios, is the audio output stage is necessarily very low powered, so the speaker is designed for efficiency rather than sound quality. They can be okay though. I like yours because of the fancy grill design and late 30s deco cabinet.

How do you parallel "D" batteries? is it positive to positive or negative to negative?

How do you parallel "D" batteries? is it positive to positive or negative to negative?

Both at once...

Both at once...

OK, so I take it that a battery clip like the one in the link below won't work in my case?

https://www.radioshack.com/products/radioshack-d-battery-holder

Despite Jeff's dour predictions , capacitor C1 would save the antenna coil if AC was improperly applied to the antenna terminals .


I didn't realize there was a capacitor in the antenna circuit to protect the coil in case the latter were inadvertently connected to 110v AC power. This will teach me not to say anything like what I said in my post without being sure of the facts.

I didn't realize there was a capacitor in the antenna circuit to protect the coil in case the latter were inadvertently connected to 110v AC power. This will teach me not to say anything like what I said in my post without being sure of the facts.

It's easy enough, unless you have the schematic in front of you!
A lot of sets don't have that capacitor, so it could've been detrimental.
They probably included it because of lightning strike is more common in rural areas.

Both at once...

Are you sure the two batteries should be connected in parallel? Because I'm only getting 1.5 volts connecting them that way...:scratch2:

I've also tried connecting 2 sets of D batteries in parallel and I'm only getting 1.4 volts, so not even close to the correct amount of volts needed to power the radio's filiments...

Well I was able to rig up a temporary battery rig for my radio and it works...Sort of.

I hooked up my signal generator up to the radio and it picks up the 456 kHz IF Signal fine (all though it picks it up all across the whole dial and not just around the 550 area of the dial), and I tweaked the IF cans and surprisingly enough they are peaked where they are supposed to be, I tried adjusting the Oscillator and Antenna adjustments on the tuning capacitor and they didn't seem to make any difference and the 600 kHz oscillator adjustment is under the chassis so I couldn't adjust that.

But I can't get it to pick up any radio stations I can't even get it to pick anything up from my signal generator tuned to various stations on the AM Band, hooked through the antenna, and the antenna coil tested fine when I tested it.

Any ideas as to what may be going on?

Are you sure the two batteries should be connected in parallel? Because I'm only getting 1.5 volts connecting them that way...:scratch2:

I've also tried connecting 2 sets of D batteries in parallel and I'm only getting 1.4 volts, so not even close to the correct amount of volts needed to power the radio's filiments...
Note I didn't advise you to put the batteries in parallel....I only advised you HOW to connect them in parallel.
The trouble with using standard alkaline D cells to supply the 2.2V filaments is that new alkaline cells are 1.5V so parallel will not give you enough voltage and series will give you too much (unless you use used batteries that are down to ~1V ). The only advantage of parallel connection is that the batteries will last longer.
One thing you could do for the filaments is connect the batteries in series and build a LM317 circuit to regulate 3V down to 2V...A filament rheostat is another solution.

Got an oscilloscope to check if the converter or oscillator tube is oscillating? And do you have a decent length of antenna wire 15-40' hooked up? If you have an antenna and the IF works then either the local osc is dead or the RF path between the antenna and the Mixer/Converter is bad....If you passed IF down the antenna and it didn't seem attenuated in comparison to injecting it at the 1st IF then that favors the Osc being dead.

Note I didn't advise you to put the batteries in parallel....I only advised you HOW to connect them in parallel.
The trouble with using standard alkaline D cells to supply the 2.2V filaments is that new alkaline cells are 1.5V so parallel will not give you enough voltage and series will give you too much (unless you use used batteries that are down to ~1V ). The only advantage of parallel connection is that the batteries will last longer.
One thing you could do for the filaments is connect the batteries in series and build a LM317 circuit to regulate 3V down to 2V...A filament rheostat is another solution.

Got an oscilloscope to check if the converter or oscillator tube is oscillating? And do you have a decent length of antenna wire 15-40' hooked up? If you have an antenna and the IF works then either the local osc is dead or the RF path between the antenna and the Mixer/Converter is bad....If you passed IF down the antenna and it didn't seem attenuated in comparison to injecting it at the 1st IF then that favors the Osc being dead.

No but someone else on here said to connect 2 D cells in parallel to get the voltage I needed for my filaments, you just happened to reply when I asked about how to connect batteries in parallel.
Anyways Rechargeable NiMH batteries are 1.2 Volts which if I connected 2 of those together I would get 2.4V which would be the correct voltage I need for the tube filaments, and they make NiMH Rechargeable D cells that are as high as 12,000 mAh, which would be more than enough juice to power the filaments.

I'm guessing the oscillator isn't running because the tubes aren't getting enough filament juice.

No but someone else on here said to connect 2 D cells in parallel to get the voltage I needed for my filaments, you just happened to reply when I asked about how to connect batteries in parallel.
Anyways Rechargeable NiMH batteries are 1.2 Volts which if I connected 2 of those together I would get 2.4V which would be the correct voltage I need for the tube filaments, and they make NiMH Rechargeable D cells that are as high as 12,000 mAh, which would be more than enough juice to power the filaments.

I'm guessing the oscillator isn't running because the tubes aren't getting enough filament juice.
Those tubes aren't that easy to source. They only used them for few years.
The 1C6 can be replaced with a 1A6.
I checked over my 2 volt battery set. At the time, I built the power supply using a transformer from a scrap VTVM. I didn't have a regulator chip at the time, so I just used discrete components.

Battery radios are the most underated old radios around. When I first started collecting I too didn't give them a second look with all those ragged wires and clips hanging out of the back. The truth is they're unique looking sets and perform very well once restored. You also don't get AC line interference, so the audio is clean. The only drawback with the wooden models is that there's usually no dial lamp, or, at best, a dim one.
Unfortunately, very often, either a surge or an attempt at hooking an AC line to them was not uncommon. Usually what happens is an instant blow-out of all the tubes. In my experience of dealing with portable battery radios, it's a 50/50 chance that the tubes are good. I've replaced the tubes on these many times.

Battery radios are the most underated old radios around. When I first started collecting I too didn't give them a second look with all those ragged wires and clips hanging out of the back. The truth is they're unique looking sets and perform very well once restored. You also don't get AC line interference, so the audio is clean. The only drawback with the wooden models is that there's usually no dial lamp, or, at best, a dim one.
Unfortunately, very often, either a surge or an attempt at hooking an AC line to them was not uncommon. Usually what happens is an instant blow-out of all the tubes. In my experience of dealing with portable battery radios, it's a 50/50 chance that the tubes are good. I've replaced the tubes on these many times.

I agree this is a very nice looking set and is also supposed to be based on one of the best designed sets Arvin made at the time, the Phantom Series.

And I think once I recap this set, and get some proper Rechargeable D cells and a good battery clip for this set I think I should be able to get this thing going. :thmbsp:

Those tubes aren't that easy to source. They only used them for few years.
The 1C6 can be replaced with a 1A6.
I checked over my 2 volt battery set. At the time, I built the power supply using a transformer from a scrap VTVM. I didn't have a regulator chip at the time, so I just used discrete components.

I'm curious, if I were to use some 1.2V NiMH rechargeable D batteries to power the filaments in this radio (2 1.2V batteries in series would give me 2.4V roughly) what kind of diode or what size of dropping resistor would I need to drop the extra .3V to get the voltage down to the 2.1V I need for the tube filaments?

Or would it not matter in this case?

Thanks for your help.

I'm curious, if I were to use some 1.2V NiMH rechargeable D batteries to power the filaments in this radio (2 1.2V batteries in series would give me 2.4V roughly) what kind of diode or what size of dropping resistor would I need to drop the extra .3V to get the voltage down to the 2.1V I need for the tube filaments?

Or would it not matter in this case?

Thanks for your help.

Any silicon diode such as the 1N400 series will drop around .6V which in my book will be close enough. I'd go so far as to suggest that two Alkaline batteries in series with the same diode will be close enough too. If you're worried about a few tenths of a volt, then put two diodes in series and when the batteries run down you can short across one and get any remaining life out.

Any silicon diode such as the 1N400 series will drop around .6V which in my book will be close enough. I'd go so far as to suggest that two Alkaline batteries in series with the same diode will be close enough too. If you're worried about a few tenths of a volt, then put two diodes in series and when the batteries run down you can short across one and get any remaining life out.

I've got several 1N4007 diodes would those work?
Would I tie the diode across the negative or positive lead of the battery clip?

Ive done a few of these 90V but the filament was 1.5v. Anyway I use 60 AA batteries for 90V power. I have soldered in connections for 45V too for other radios. I doubt the AA's cost much more than the 9V ones but you have to solder holders together and yes more time involved. About every 3 years +/- 1 they need replacing if they are a good brand.

I like the sound of the battery radios. They dont have much static type sounds as they arent hooked to your homes power supply. If your fortunate enough to have a long wire antenna that will increase the sound too. My outdoor antenna is about 90 feet long.

Ive done a few of these 90V but the filament was 1.5v. Anyway I use 60 AA batteries for 90V power. I have soldered in connections for 45V too for other radios. I doubt the AA's cost much more than the 9V ones but you have to solder holders together and yes more time involved. About every 3 years +/- 1 they need replacing if they are a good brand.

I like the sound of the battery radios. They dont have much static type sounds as they arent hooked to your homes power supply. If your fortunate enough to have a long wire antenna that will increase the sound too. My outdoor antenna is about 90 feet long.

Reminds me of what I did in the mid-50's. I would dig through the trash bin behind the TV shop for battery packs for a Zenith TO or similar. The "A" side was usually dead, but the "B" side was good for about 75 or so volts.
That side was usually sealed in tar and lasted quite a while. :thmbsp:

American ingenuity! :thmbsp:

I did forget to add that the smaller voltage battery will often just last hours as they have draw. The 90 volt pack will last for the life of the batteries. I did buy a cheap brand of AA's and I got what I paid for, they lasted about a year.

American ingenuity! :thmbsp:

I did forget to add that the smaller voltage battery will often just last hours as they have draw. The 90 volt pack will last for the life of the batteries. I did buy a cheap brand of AA's and I got what I paid for, they lasted about a year.

On a side note and slightly OOT, it always amazed me that anyone would buy a battery only tube radio. "B" batteries were never cheap!
I'm referring to the time when most homes had electricity. Portable, battery only radios were made until about 1956.
Three way portables were only about $5 to $8 dollars more and you can use them all year.:scratch2:

On a side note and slightly OOT, it always amazed me that anyone would buy a battery only tube radio. "B" batteries were never cheap!
I'm referring to the time when most homes had electricity. Portable, battery only radios were made until about 1956.
Three way portables were only about $5 to $8 dollars more and you can use them all year.:scratch2:

In my case, it was for safety... as a kid, I was always taking my radio into the bathroom, a battery only set with no cord was much safer. “B” batteries were great xmas and birthday gifts :thmbsp:

jr

My step mom has a Coronado set that has three way power. it had a compartment and a plug for a 90V/1.5v A/B battery (i think). I think it was late 40s or early 50s. I'll find more info next time I visit.

I also have an Emerson 508 (battery only) and a Motorola 5A7A (three way) that use a 67 volt B and a D size A.

EDIT: nabbed photos off epay. empty box lol.

two 45 volt "B"s and two 4.5 volt "A"s. hmmmm.......

My step mom has a Coronado set that has three way power. it had a compartment and a plug for a 90V/1.5v A/B battery (i think). I think it was late 40s or early 50s. I'll find more info next time I visit.

I also have an Emerson 508 (battery only) and a Motorola 5A7A (three way) that use a 67 volt B and a D size A.

EDIT: nabbed photos off epay. empty box lol.

two 45 volt "B"s and two 4.5 volt "A"s. hmmmm.......
The radio was made by Warwick. I wonder what battery life was like? Using a 9 volts "A" source makes the switching circuitry simpler between line and battery.
My luggable Emerson 523 uses the same battery compliment.

On a side note and slightly OOT, it always amazed me that anyone would buy a battery only tube radio. "B" batteries were never cheap!
I'm referring to the time when most homes had electricity. Portable, battery only radios were made until about 1956.
Three way portables were only about $5 to $8 dollars more and you can use them all year.:scratch2:

The 1st one I fixed was my Dad's farm set before they had electric. Its a 1949 I think. Airline model. My Dad told me even back then the batteries were expensive. They used it until quite a while after they got electric then gave it to an Uncle who had electric but no radio and he used it until around 1960 I think.

It needed and needs a decent antenna run to pick up much, maybe 10 foot minimum so isnt much of a portable. It only has a screw to attach an antenna wire to it. A built in antenna would have been better. My Dad ran an antenna around the outside of the house and stapled it on so they could listen to the Grand Ole Opry on the weekends, plus local stations during the week.

All that said, I agree, anyone with electric was better off with a plug in electric option.

The 1st one I fixed was my Dad's farm set before they had electric. Its a 1949 I think. Airline model. My Dad told me even back then the batteries were expensive. They used it until quite a while after they got electric then gave it to an Uncle who had electric but no radio and he used it until around 1960 I think.

It needed and needs a decent antenna run to pick up much, maybe 10 foot minimum so isnt much of a portable. It only has a screw to attach an antenna wire to it. A built in antenna would have been better. My Dad ran an antenna around the outside of the house and stapled it on so they could listen to the Grand Ole Opry on the weekends, plus local stations during the week.

All that said, I agree, anyone with electric was better off with a plug in electric option.
I have a post-war Zenith four tube farm set.
I got lucky and picked up two battery eliminators intended for farm sets at a swap meet a while back. I have one in the Zenith.

OK so I had ordered some capacitors for this radio over at AES (Antique Electronic Supply) and I had put the order in on Friday (November 27) and I had gotten the order confirmation email from them on Sunday (November 29) and I checked the tracking on my package and it says that a shipping label was made for my order on November 29 (Sunday) and that the postal service was waiting to receive the package, and that's the last update on my parts order from AES.

Here it is December 2, and its still not left AES's headquarters, (according to the tracking number as of today) and I paid the extra money for priority mail.

Does anyone know what's going on?

Dunno. AES is usually pretty quick, but they're in Arizona and I'm in New Mexico. It's probably holiday related delays.

Dunno. AES is usually pretty quick, but they're in Arizona and I'm in New Mexico. It's probably holiday related delays.

I messaged them and they said it was because of all of the online black friday sales that more or less overwhelmed the postal service there, which is understandable because I did hear about that on the news on the radio.

A little update, I got my 2 D-Cell Battery Clip today that I ordered from Radio Shack last Week, and I wired it up just like you guys suggested with a couple of 1N4007 Diodes wired in series with the Positive wire for the Battery clip and that then in turn was wired to the radio's "A" Battery hookups.

I was able to get the radio to work for a little bit (with my signal generator hooked up for a signal source) and I was able to get the test tone to go through the Antenna hookups properly (it was actually coming in where it was supposed to on the dial and not all across the dial like it did before).

Then going through the grid cap of the 1C6 tube I was also able to get the signal through there as well (but it was coming in all across the dial and not at just one spot like it was supposed to).

But then when I went to try and adjust the IF Cans to make sure they were peaked correctly the signal would cut in and out and then it finally completely cut out to the point that I can't get anything out of the radio audio wise anymore, and I did check the batteries to make sure there was enough juice and there was plenty of juice in the batteries, and they were putting out 2.3 Volts.

I'm still waiting on my capacitors (checked the tracking and they are supposedly arriving on Friday (which is kind of rediculous because I shouldn't of had to wait almost 3 weeks for my parts to come like this).

Anyone have any ideas as to what may have happened to my radio?

Thanks.

Would any of the batteries listed in the link below work for the "A" battery on this radio?

https://www.batteriesplus.com/battery/sla-sealed-lead-acid/2

Would any of the batteries listed in the link below work for the "A" battery on this radio?

https://www.batteriesplus.com/battery/sla-sealed-lead-acid/2
I didn't know 2 volt lead-acid rechargable batteries were still available.
Now, you'll have to build a charger!

Anyone have any ideas as to what may have happened to my radio?

Thanks.

Looks like nobody's chiming in. If you were turning the IF adjustments with the oscillator dead, there will be no IF signal for the adjustments to 'peak' to. So they're probably 'waay outa whack. To get them back on peak, inject a 456 khz signal. Keep attenuating the level as needed as they approach the peak. Once on peak, attenuate a little more and get it as sharp as possible.

Then start looking for why the osc. isn't running. For a start, check for continuity of the osc coil's primary and secondary windings.

Looks like nobody's chiming in. If you were turning the IF adjustments with the oscillator dead, there will be no IF signal for the adjustments to 'peak' to. So they're probably 'waay outa whack. To get them back on peak, inject a 456 khz signal. Keep attenuating the level as needed as they approach the peak. Once on peak, attenuate a little more and get it as sharp as possible.

Then start looking for why the osc. isn't running. For a start, check for continuity of the osc coil's primary and secondary windings.


Well that's the thing it was "working" (I was able to inject a 456 kHz signal into the radio and it was picking it up but it was intermittent) and now when I try to inject a 456 kHz signal into the radio it won't pick it up at all period.

Although I think I figured out part of my problem, my temporary "A" battery rig is only putting out about 150 mA of current and the radio's filaments require over 500 mA of current. So I think I need either brand new D-Cell batteries or some high output current rechargeable D-Cell batteries (like some 10,000 mAh NiMH rechargeable batteries.)

As for the oscillator coil measurements goes, I tried measuring it with my multimeter and all I get is an O. L. Reading on my multimeter when trying to measure it, it's the same way with the antenna coil and the IF coils as well and I'm pretty sure there's no way that both IF coils and the Antenna Coil and the Oscillator coil could of died all at once especially seeing as when I first got it and took it apart and measured everything they all tested fine then...:scratch2:

i'd wait for the caps and replace them before worrying about anything else.

OK so a little update on this radio, I got the radio recapped yesterday and I also got a set of 2500 mAH NiMH rechargeable D batteries from Harbor Freight and then a Charger for them at Menard's (they were the only place near me that had a universal battery charger in stock without having to travel to Mishawaka or South Bend which is over a half hour away from me.)

And I charged the batteries over night and installed them into my battery clip and turned on my radio with my signal generator hooked up to the antenna wire and sure enough I was signal through (albeit at the wrong frequency, it was coming in at 453 kHz rather than 456 kHz) and so I realigned the IF cans so that they were coming in at 456 kHz instead.

But then shortly after that the radio faded out and I checked my D batteries for my "A" supply and they were still putting out a charge so then I turned the radio back on again and the radio started working again but then it faded out again.

Also something I've noticed with my radio is that one of the IF cans on this radio is a replacement and when I would power on this radio and once it warms up, the radio makes a short burst of white noise and then it goes away like the radio is trying to pick some stations or trying to function but it can't quite function properly.

Also another weird thing I've noticed about this radio is that this radio will only operate at between 2.2 volts and 2.4 V on the filaments, if I try to use the recommended 2.1 Volts, the radio won't operate.

Any ideas as to what might be going on with the radio?

OK so a little update on this radio, I got the radio recapped yesterday and I also got a set of 2500 mAH NiMH rechargeable D batteries from Harbor Freight and then a Charger for them at Menard's (they were the only place near me that had a universal battery charger in stock without having to travel to Mishawaka or South Bend which is over a half hour away from me.)

And I charged the batteries over night and installed them into my battery clip and turned on my radio with my signal generator hooked up to the antenna wire and sure enough I was signal through (albeit at the wrong frequency, it was coming in at 453 kHz rather than 456 kHz) and so I realigned the IF cans so that they were coming in at 456 kHz instead.

But then shortly after that the radio faded out and I checked my D batteries for my "A" supply and they were still putting out a charge so then I turned the radio back on again and the radio started working again but then it faded out again.

Also something I've noticed with my radio is that one of the IF cans on this radio is a replacement and when I would power on this radio and once it warms up, the radio makes a short burst of white noise and then it goes away like the radio is trying to pick some stations or trying to function but it can't quite function properly.

Also another weird thing I've noticed about this radio is that this radio will only operate at between 2.2 volts and 2.4 V on the filaments, if I try to use the recommended 2.1 Volts, the radio won't operate.

Any ideas as to what might be going on with the radio?

First of all, a fully charged 2 volt lead-acid puts out 2.2volts. This voltage is what the radio was designed to use.
Did you check the tubes on a good tube checker. You probably have a weak osc-mixer tube. Increasing the filament voltage, will increase the emission.

First of all, a fully charged 2 volt lead-acid puts out 2.2volts. This voltage is what the radio was designed to use.
Did you check the tubes on a good tube checker. You probably have a weak osc-mixer tube. Increasing the filament voltage, will increase the emission.

I was using a set of 1.2 V NiMH rechargeable D Cells, not the 2V Lead-Acid battery I had previously linked here and asked about.

Secondly I don't have a tube tester capable of testing the old style 4, 5, 6 and 7 pin tubes, so I can't check the tubes unfortunately.

I've tried to acquire one but everytime I find one they usually want over $100 for it, which I can't afford anything like that right now.

Since your set has AVC why not monitor that voltage to get a handle on what's going on? You'll want to use a VTVM, a scope, or a digital volt meter connected to the bottom side of R3(2meg). When the set is working does your AVC voltage seem to work normally with and without a signal tuned in? AVC voltage normally will be negative with a strong signal and become more positive as you de-tune the station. If the local oscillator isn't running you loose AVC action. If AVC voltage continues to respond to tuning then when the audio fades, then most likely you have an issue in the audio sections. When the radio is working correctly you can also align the IF's to the most negative voltage on the AVC line. There's really no need to rely on listening to an audio tone through the speaker.

Edit R3 not R4

I meant AVC voltage at bottom side of R3, not R4 as I fist posted.
Edited above post.

I was using a set of 1.2 V NiMH rechargeable D Cells.....


;) Looking at the tube compliment posted in your first post , I can not believe a pair if D cells in series is anywhere close to powerful enough to light all those filaments .

Looks like nobody's chiming in. If you were turning the IF adjustments with the oscillator dead, there will be no IF signal for the adjustments to 'peak' to. So they're probably 'waay outa whack. To get them back on peak, inject a 456 khz signal. Keep attenuating the level as needed as they approach the peak. Once on peak, attenuate a little more and get it as sharp as possible.

Then start looking for why the osc. isn't running. For a start, check for continuity of the osc coil's primary and secondary windings.

We didn't chime in because the OP was waiting for the parts.

;) Looking at the tube compliment posted in your first post , I can not believe a pair if D cells in series is anywhere close to powerful enough to light all those filaments .

They are 2500 mAh batteries, so more than enough juice to power the filaments (the filaments require around 540 mA).

We didn't chime in because the OP was waiting for the parts.

Well I got the parts in and installed, and its looking like I might have a bad 1C6 tube which can be subbed out for a 1A6, 1C7 or a 1D7, whichever is more readily available.

Does anyone on here have either a 1C6, 1A6, 1C7 or a 1D7 tube that is known to be good that they could send me, or know if there are any for sale on fleabay for sale for relatively inexpensive?

Thanks!

UPDATE: I found a set of NOS Ken-Rad 1C6 tubes on feebay for $16 plus shipping.

UPDATE: I figured out what my problem is, its the IF Cans, apparently at some point in time in this radio's history both IF Cans were replaced, and whomever did the replacement installed two IF Cans of with two Different IF Frequencies that were completely different from the original IF Frequency of the radio! :nono: :no:

The 1st IF Can was replaced with an IF Can with an IF Frequency of 455 kHz and the 2nd IF Can was replaced with an IF Can with an IF Frequency of 475 kHz, and the radio's original IF Frequency according to the Riders was 465 kHz which might explain why this radio isn't working right.

When I feed a signal through my antenna hookup on the radio using my signal generator I can hear the signal coming through albeit very faintly (I have to have the volume turned clear up to hear it) and with the signal Generator's High Output signal being used the signal comes through at a somewhat normal volume level, which means that what my radio's problem is isn't the tubes or a dead oscillator coil or too weak of batteries, what the problem is, is the radio is trying to operate with two IF Cans of different frequencies.

So I'm not quite sure how I would fix this issue...:sigh::scratch2:

It should be possible to align the IF cans 10KHz off designed frequency. Nothing to loose trying it. If they don't peak in range of adjustments you could try tacking pF caps across windings to see if you can get more range.

It should be possible to align the IF cans 10KHz off designed frequency. Nothing to loose trying it. If they don't peak in range of adjustments you could try tacking pF caps across windings to see if you can get more range.

Well what's interesting is that the 1st IF can's IF Frequency is 10 KC lower than the original IF Frequency, and the 2nd IF can's IF Frequency is 10 KC higher than the original IF Frequency of 465 kHz, which I'm not sure what the point of that would of been but its kind of bizarre.

And I guess I can see what happens as far as trying to align the IF cans to the original 465 kHz IF Frequency.

UPDATE: I found a set of NOS Ken-Rad 1C6 tubes on feebay for $16 plus shipping.
It's unfortunate that the owner of ESRC passed away.
They had those odd-ball tubes reasonable. :thmbsp:

It's unfortunate that the owner of ESRC passed away.
They had those odd-ball tubes reasonable. :thmbsp:

Yes it is unfortunate. :sigh:

Since your set has AVC why not monitor that voltage to get a handle on what's going on? You'll want to use a VTVM, a scope, or a digital volt meter connected to the bottom side of R3(2meg). When the set is working does your AVC voltage seem to work normally with and without a signal tuned in? AVC voltage normally will be negative with a strong signal and become more positive as you de-tune the station. If the local oscillator isn't running you loose AVC action. If AVC voltage continues to respond to tuning then when the audio fades, then most likely you have an issue in the audio sections. When the radio is working correctly you can also align the IF's to the most negative voltage on the AVC line. There's really no need to rely on listening to an audio tone through the speaker.

Edit R3 not R4

I did check the voltage at the AVC line resistor (R3) and it does respond like its supposed to but the audio is not very loud unless I use my signal generator's "HI" output connection, and then it comes out at a more "normal" volume level.

I have attributed that fact to what I believe is a faulty 1C6 Tube, because the oscillator seems to be "running" but not very well, and both 1A4 tubes respond with a hum when I touch their grid caps but nothing when I touch the grid cap on the 1C6, I get no hum out of it.

So I'm thinking I'm on the right track and just about have this thing going.

Did you peak both if transformers to 465 khz?

jr

Did you peak both if transformers to 465 khz?

jr

Yes I did, and when I would try to inject the 1400 kHz signal in through the antenna leads so I could work on the dial tracking/alignment I can barely hear the signal generator coming through at full volume using the attenuated output signal at 50% output (the highest amount of output that my signal generator can do), but then the unattenuated output allows the signal generator to be heard at a somewhat normal volume level.

OK so a little update, I got my NOS 1C6 tubes in today and my radio is now mostly working, it is now definitely oscillating (I did the holding another radio up next to it trick and that second radio was picking up this radio's oscillator signal).

But its still not picking up any stations unfortunately.

I've got the IF cans Aligned to 465 kC the Best I can (seeing as neither of the IF cans in this radio are original to this radio and are not 465 kC cans).

So I'm kind of not sure where to go from here now.

Here's a video showing what the radio is currently doing:

https://youtu.be/e702udS6aiM

OK, so another Update, it seems I had a bit of a dislexic moment because this radio's IF Frequency is 456 not 465 like I had been saying the entire time...:stupid: :eek:

Anyways So I realigned the radio to 456 KC and the tuner seems to be working better with the signal generator, but its still not picking up any stations on its own with a long wire antenna hooked up to it... :headscrat

So I'm wondering if my 30 Tube is bad as well because that tube controls the Second Detector and the AVC circuit which the AVC is working as it should be but I'm wondering if maybe the detector portion of the 30 tube is bad or at least not in very good shape.

Anyone here have a known good 30 tube they could spare me? If not I guess I could get one from ebay.

The 30 tube is a single triode configured as a grid leak detector. Notice the plate tied to ground. Since you say you have AVC voltage changes you can be sure the 30 is working. Can you see AVC voltage change when tuning on and off a known local radio station? Make sure C8 is .0005uf. If it's too large it will start filtering the audio.

The 30 tube is a single triode configured as a grid leak detector. Notice the plate tied to ground. Since you say you have AVC voltage changes you can be sure the 30 is working. Can you see AVC voltage change when tuning on and off a known local radio station? Make sure C8 is .0005uf. If it's too large it will start filtering the audio.

No there is no change in the AVC voltage when trying to tune in a known local station. In fact trying to tune anywhere on the dial the AVC voltage stays pretty constant at around positive 15 mV and doesn't go negative at any point when tuning across the dial with just a long wire antenna attached.

It does however work when using the signal generator but like I said previously I have to use my signal generator's unattenuated high volume output signal output in order for the radio to be able to pick up the signal from the signal generator and be able to affect the AVC voltage.

So I'm not sure what's going on here.

Did you see the video I posted of my radio and what it's doing with just an antenna hooked up?

No there is no change in the AVC voltage when trying to tune in a known local station. In fact trying to tune anywhere on the dial the AVC voltage stays pretty constant at around positive 15 mV and doesn't go negative at any point when tuning across the dial with just a long wire antenna attached.

It does however work when using the signal generator but like I said previously I have to use my signal generator's unattenuated high volume output signal output in order for the radio to be able to pick up the signal from the signal generator and be able to affect the AVC voltage.

So I'm not sure what's going on here.

Did you see the video I posted of my radio and what it's doing with just an antenna hooked up?

What you say indicates is that your local oscillator is either not running, or it's running at an incorrect frequency.

When you inject an IF frequency from you signal generator you are forcing the correct signal through the IF transformes, which in turn gets detected by the 30 tube and produces AVC voltage. The key here is you're not relying on the local oscillator to mix with the incoming rf signal to produce that outcome.

In normal operation the rf signal mixes with the local oscillator to create beat frequencies equal to the sum and difference of the two. One of those beat frequencies is the IF signal. You should double check that you didn't replace a cap around the 1C6 tuned circuit with a incorrect value and also verify the two winding's in the oscillator coil(#17484) have continuity.

...it is now definitely oscillating (I did the holding another radio up next to it trick and that second radio was picking up this radio's oscillator signal).

What is the other radio's dial setting when it picks up the Coronado's oscillator? And what is the Coronado's dial setting? The diff between the settings is the Coronado's IF frequency (assuming both radios' dial calibrations are reasonably correct).

For example, if the Coronado's dial is at 550, its oscillator should be heard around 1010 on the other radio. Or if Coronado's at 1140, you should hear the osc at about 1600.

What you say indicates is that your local oscillator is either not running, or it's running at an incorrect frequency.

When you inject an IF frequency from you signal generator you are forcing the correct signal through the IF transformes, which in turn gets detected by the 30 tube and produces AVC voltage. The key here is you're not relying on the local oscillator to mix with the incoming rf signal to produce that outcome.

In normal operation the rf signal mixes with the local oscillator to create beat frequencies equal to the sum and difference of the two. One of those beat frequencies is the IF signal. You should double check that you didn't replace a cap around the 1C6 tuned circuit with a incorrect value and also verify the two winding's in the oscillator coil(#17484) have continuity.

Well I checked all of the original "dogbone" resistors in the radio (which are all 1/4 watt resistors according to the service manual) and they are all within spec.

When I recapped this radio, I used orange drops for all but 2 of the capacitors, (the 2 capacitors that I didn't use orange drops on were the .0005 MFD 600 V caps that I had to use Silver Mica caps for because they didn't have any orange drops that went down that low in value), and I made sure that I put the caps in the right spot, so I don't think its the caps or the resistors.

When I first got this radio (and after I realized that someone had attempted to wire a power cord to the antenna wire terminal strip) I had tested the antenna coil and the oscillator coil to make sure they weren't damaged, and they both tested fine.

But then when I was checking voltages around the power switch (where the battery wires wired into the switch), I had accidentally let out some magic smoke but I couldn't tell where it came from, but all I know is that ever since then the antenna coil and the oscillator coil have been reading O. L. on my multimeter, and I'm not sure why because the coils don't look burnt and they don't look damaged either.

Do you need some pictures of the underside of the radio so you can see what the radio looks like underneath and see if you can see anything out of place?

But then when I was checking voltages around the power switch (where the battery wires wired into the switch), I had accidentally let out some magic smoke but I couldn't tell where it came from, but all I know is that ever since then the antenna coil and the oscillator coil have been reading O. L. on my multimeter, and I'm not sure why because the coils don't look burnt and they don't look damaged either.


Well if by O.L. you mean they are reading infinite ohms then I think you've found a problem. Those coils should show a fairly low resistance.

What is the other radio's dial setting when it picks up the Coronado's oscillator? And what is the Coronado's dial setting? The diff between the settings is the Coronado's IF frequency (assuming both radios' dial calibrations are reasonably correct).

For example, if the Coronado's dial is at 550, its oscillator should be heard around 1010 on the other radio. Or if Coronado's at 1140, you should hear the osc at about 1600.

Well the strange thing is that the Coronado's tuner is set to around 640 AM and the tuner on my Panasonic RF-511 AM/FM transistor radio is set to about the same spot and that's where I hear the Coronado's Oscillator on the Transistor radio is at 640 AM on the dial or very close to that spot anyways and when I go up the dial the oscillator noise kind of dies off the higher up the dial the tuner goes (on both radios).

So I'm guessing my oscillator is working but not correctly...:scratch2:

But then when I was checking voltages around the power switch (where the battery wires wired into the switch), I had accidentally let out some magic smoke but I couldn't tell where it came from, but all I know is that ever since then the antenna coil and the oscillator coil have been reading O. L. on my multimeter, and I'm not sure why because the coils don't look burnt and they don't look damaged either.


Well if by O.L. you mean they are reading infinite ohms then I think you've found a problem. Those coils should show a fairly low resistance. Try putting your meter on diode check and see if you get a beep across each winding. If no you have an open winding, that is providing your meter beeps when you touch the two probes together.

Well if by O.L. you mean they are reading infinite ohms then I think you've found a problem. Those coils should show a fairly low resistance.

Well I'm guessing this radio is going to have to be a shelf queen I'm guessing, because those coils are probably going to be darn near impossible to find, and I doubt they could be repaired.

Well I'm guessing this radio is going to have to be a shelf queen I'm guessing, because those coils are probably going to be darn near impossible to find, and I doubt they could be repaired.

Post us a couple pictures of what they look like. I doubt they're anything too unique. What you have there is a very basic broadcast band only radio.

Post us a couple pictures of what they look like. I doubt they're anything too unique. What you have there is a very basic broadcast band only radio.

Ok, here's the Oscillator and antenna coils.

Ok, here's the Oscillator and antenna coils.

Looking at the schematic I'm in disbelief that you opened a winding in both by simply taking voltage measurements. :no:
Are you 100 percent positive that both transformers have at least one winding open? Maybe you should post us a couple pictures of the entire bottom side the chassis, just in case you're overlooking something obvious.

These Meissner numbers will replace them. They use to be common as dirt.
14-1010 standard broadcast band antenna coil
14-4034 456kc oscillator coil

I'm sure there's other manufactures numbers that would work, as well as pulling them out of junked radios. The oscillator coil should ideally be for 456kc, but as mentioned you can usually walk the IF's off frequency a small amount.

Looking at the schematic I'm in disbelief that you opened a winding in both by simply taking voltage measurements. :no:
Are you 100 percent positive that both transformers have at least one winding open? Maybe you should post us a couple pictures of the entire bottom side the chassis, just in case you're overlooking something obvious.

These Meissner numbers will replace them. They use to be common as dirt.
14-1010 standard broadcast band antenna coil
14-4034 456kc oscillator coil

I'm sure there's other manufactures numbers that would work, as well as pulling them out of junked radios. The oscillator coil should ideally be for 456kc, but as mentioned you can usually walk the IF's off frequency a small amount.

Well as I had stated previously, both IF cans are replacements, the 2nd IF Can is a Meisner replacement rated to cover the frequencies of 450 KC to 475 KC, and the 1st IF can is a generic 455 KC replacement.

As for the Oscillator and Antenna Coils, I had already removd the Oscillator coil from the chassis and I double checked it and it definitely doesn't give me any sort of resistance measurements all it gives me is an O. L. reading on my DMM, as for my antenna coil it also doesn't give me any sort of resistance readings as well, I've tried every single terminal combination (because I wasn't sure which terminals were the primary and secondary terminals), and I get the same O. L. readings on the antenna and oscillator terminals.

I can get you a picture of the underside but like I said the Oscillator coil isn't going to be there because I removed it.

...I hear the Coronado's Oscillator on the Transistor radio is at 640 AM on the dial or very close to that spot anyways and when I go up the dial the oscillator noise kind of dies off the higher up the dial the tuner goes (on both radios).

So I'm guessing my oscillator is working but not correctly...:scratch2:

The osc is not running, period. Just a note on basic superhet practice (for convenience, say the IF is 460): When the radio is set up and aligned correctly, the osc will always track 460 on the high side of the received signal. So whatever station is tuned in, its signal will 'beat', or heterodyne, against the osc, generating the Intermediate Frequency of 460 khz, which is then sent downstream, amplified and detected.

Um.. what does O.L. stand for?

The osc is not running, period. Just a note on basic superhet practice (for convenience, say the IF is 460): When the radio is set up and aligned correctly, the osc will always track 460 on the high side of the received signal. So whatever station is tuned in, its signal will 'beat', or heterodyne, against the osc, generating the Intermediate Frequency of 460 khz, which is then sent downstream, amplified and detected.

Um.. what does O.L. stand for?

Ok, that's what I figured.

O. L. I believe means OverLoad(ed).
Anyways that's just a guess, because every single Digital Multimeter I've ever owned always showed some variation of the O. L. designation for the "infinite" or "open circuit" reading on the multimeter display.

Anyways I think I'm going to need new Osc. and Ant. Coils, or at least an oscillator coil.

Just for giggles does your meter show zero ohms when you touch both test probes together?

I guess you need to make the call of how badly you want to fix that radio. I looked on ebay and see a few 14-4034 Osc coils but sellers apparently think they're setting on the last ones on the planet.

Just for giggles does your meter show zero ohms when you touch both test probes together?


It measures 0.3 Ohms when I touch the probes together. Why?

I guess you need to make the call of how badly you want to fix that radio. I looked on ebay and see a few 14-4034 Osc coils but sellers apparently think they're setting on the last ones on the planet.

Well I've already sunk about $50 into this radio...:scratch2:

Just for giggles does your meter show zero ohms when you touch both test probes together?

I guess you need to make the call of how badly you want to fix that radio. I looked on ebay and see a few 14-4034 Osc coils but sellers apparently think they're setting on the last ones on the planet.

I just looked on feebay and those coils are only $15 or so, which isn't too bad.

Just picked up one of these Oscillator Coils for $13 with free shipping.

It measures 0.3 Ohms when I touch the probes together. Why?


There's always a little contact resistance at the connectors and prob tips.

There's always a little contact resistance at the connectors and prob tips.

Yes, which I was aware of, but what does that have to do with your "just for giggles" experiment about my oscillator and antenna coils being bad or not?

OK here's a shot of the undercarriage of this radio.

Is there anything that looks out of place to you guys (besides the previously removed oscillator coil)?

Yes, which I was aware of, but what does that have to do with your "just for giggles" experiment about my oscillator and antenna coils being bad or not?

I didn't understand how you'd expect the radio to pick up stations all the while knowing those coils were open. But in the end the important things is you're making good headway. ;)

I didn't understand how you'd expect the radio to pick up stations all the while knowing those coils were open. But in the end the important things is you're making good headway. ;)

Ok, sorry when it comes to stuff like that I'm slower than molasses in the winter on the uptake.

OK, so I was looking at the original Oscillator Coil for this radio and I noticed that all of the wires coming from the coil are there and going to their respective terminal except for one, one of the wires is missing coming from the coil to the terminal and the coil has one spot that looks like it was chewed on by a mouse or some other kind of rodent, and I suspect that this may be why this oscillator coil is bad...:smoke:

Actually scratch that 3 of the 4 wires were broken from the places where they came out of the coil.

UPDATE: Antenna Coil is still good, its just the oscillator coil that was bad, and I think it was chewed up by a mouse or some other rodent.

UPDATE: Still waiting for the Oscillator coil to come in the mail (It had free shipping, which means USPS 1st Class Mail, which means it will probably take its dear sweet time getting here).

But at least its going to be an inexpensive fix and its not going to be a shelf queen like I thought it was going to be originally. :thmbsp:

While we're waiting on parts.. back in post 64 I mentioned that the 30 tube is a single triode configured as a grid leak detector, which it is not. I intended to say configured as a diode, notice the plate tied to the cathode(both grounded). When I came back and reread that just now it jumped right out at me. :o Anyhow I just wanted to make that clarification so as to not confuse anyone else reading along. And you guys should have called me on that one. :D

While we're waiting on parts.. back in post 64 I mentioned that the 30 tube is a single triode configured as a grid leak detector, which it is not. I intended to say configured as a diode, notice the plate tied to the cathode(both grounded). When I came back and reread that just now it jumped right out at me. :o Anyhow I just wanted to make that clarification so as to not confuse anyone else reading along. And you guys should have called me on that one. :D

Thanks for the clarification. :D

UPDATE: My Oscillator Coil Came in the mail today and I got it installed and powered on the radio and it works! :thmbsp: :music:

I'll need to touch up the alignment a little bit as it is a little distorted sounding when its tuned into a station, but other than that its receiving a ton of stations and it gets really loud too!

See video link below to see a video I made of the radio in action.

https://youtu.be/8CO-H8qR_NU

:thmbsp:Nice!

Bravo! Very, very nice.

Bravo! Very, very nice.

Thanks! This was my first repair where I actually had to replace more than just the caps or resistors in one of these radios, and it was my first farm radio that I've ever worked on.

And to be honest, with just my 2 1.2v NiMH rechargeable D batteries installed in a regular old Radio Shack Battery Clip wired up to a 1N4007 Diode for voltage drop the radio actually played for about 3 1/2 hours with plenty of juice to spare and the batteries weren't even fully charged! :yes::music:

Like a Boss! Coool, dude! :rockon::guitar::banana:

Like a Boss! Coool, dude! :rockon::guitar::banana:

Thanks! I think this will be my new Go To radio for Night Time DX'ing since it's a battery set and I could drag it out into a park out in the middle of nowhere and string up an antenna and just cruise the dial and see how many distant stations I can get in. :thmbsp::banana::D

Glad you have it fixed! Enjoy

Hey you did good. :thmbsp: Seems to be working really well, and it's quite sensitive. That will be very interesting once you get outdoors away from all the modern rf noise sources. If you have a scope with a DC coupling you can monitor the AVC voltage line and watch the trace move up and down as you change the tuning.

Hey you did good. :thmbsp: Seems to be working really well, and it's quite sensitive. That will be very interesting once you get outdoors away from all the modern rf noise sources. If you have a scope with a DC coupling you can monitor the AVC voltage line and watch the trace move up and down as you change the tuning.

Yes I do have an oscilloscope, and I think it does have DC Coupling but I'm not sure, the 'scope I have is a Tektronix Model 453 that is a Hybrid (part solid state part Nuvistor Tube powered).

How do I know if the 'scope I have has DC Coupling?

Yes I do have an oscilloscope, and I think it does have DC Coupling but I'm not sure, the 'scope I have is a Tektronix Model 453 that is a Hybrid (part solid state part Nuvistor Tube powered).

How do I know if the 'scope I have has DC Coupling?

You don't need a scope for this - a DC voltmeter will work.

Tis true but it's more fun watching the scope trace in a dimly lite room. Plus it's a great way to get comfortable working all those intimidating controls. :no: Most modern scopes have a AC-DC coupling switch near each channel input.

...since it's a battery set and I could drag it out into a park out in the middle of nowhere and string up an antenna and just cruise the dial and see how many distant stations I can get in. :thmbsp::banana::D
After a radio's been fixed and working good, often you can squeeze just a bit more gain out of the IFs; tune to a weak station that's almost "down in the grass" and then re-tweak each of the IF trimmers for absolute max gain. Often just the tiniest fraction of a turn makes a difference.

BTW, does the tuning spread match the dial markings pretty well?

Tis true but it's more fun watching the scope trace in a dimly lite room. Plus it's a great way to get comfortable working all those intimidating controls. :no: Most modern scopes have a AC-DC coupling switch near each channel input.

Yes, I just looked at the front panel on mine and it does have a switch for selecting different coupling options including DC.

My Oscilloscope has 3 different probes 2 of them say 10x 100MHz 13pF 10MΩ 2 meter, and the 3rd one says 10x 10pF 10MΩ 2 meter, does anyone know what that's referring to?

See picture below.

My Oscilloscope has 3 different probes 2 of them say 10x 100MHz 13pF 10MΩ 2 meter, and the 3rd one says 10x 10pF 10MΩ 2 meter, does anyone know what that's referring to?

10x means it's a divide by 10 probe. So if you're measuring 10v it will look like 1v per division on the screen. Some scopes have both 1x and 10x positions marked on the volts per division selector. 10X also loads the measured signal less than 1X. The 13 and 10pf are the probes internal capacitance. Those aren't too critical until you're looking at square wave shapes. There's generally a capacitance matching trimmer for each channel input. You may have a calibration square wave terminal on the front panel you can connect the probe to and then you adjust the capacitance trimmer for that channel so the waveshape has square edges. 10M is the probes impedance.

[edit] Actually it's more likely the input capacitance trimmer is in the probe housing. You do have a 1kh calibration signal on the front panel left side.

10x means it's a divide by 10 probe. So if you're measuring 10v it will look like 1v per division on the screen. Some scopes have both 1x and 10x positions marked on the volts per division selector. 10X also loads the measured signal less than 1X. The 13 and 10pf are the probes internal capacitance. Those aren't too critical until you're looking at square wave shapes. There's generally a capacitance matching trimmer for each channel input. You may have a calibration square wave terminal on the front panel you can connect the probe to and then you adjust the capacitance trimmer for that channel so the waveshape has square edges. 10M is the probes impedance.

[edit] Actually it's more likely the input capacitance trimmer is in the probe housing. You do have a 1kh calibration signal on the front panel left side.

Can this 'scope be used to calibrate a signal generator, or a frequency counter?

A frequency counter is much more precise at measuring frequency than a scope, so the counter could be used to calibrate the frequency of the signal generator, and then the signal generator could be used to calibrate the scope sweep time. Doing the opposite order would result in much larger errors.

Note that later and more expensive scopes may have built in measurement cursors to get a more precise measurement of time/frequency than just eye-balling the display, but eventually these have to be calibrated against a standard frequency source.

Really modern scopes are all digital sampling types, and the sampling rate is crystal controlled, so the scope really contains a calibrated reference.

Note that later and more expensive scopes may have built in measurement cursors to get a more precise measurement of time/frequency than just eye-balling the display, but eventually these have to be calibrated against a standard frequency source.

Really modern scopes are all digital sampling types, and the sampling rate is crystal controlled, so the scope really contains a calibrated reference.

Ok, that makes sense. Thanks for explaining that to me. :yes:

OK, so a little update: This radio had been working like a champ for the past week and a half and then today I was listening to it and the stations were bleeding over onto each other on the upper end of the dial and so I turned it off and went to turn it back on to see if it had cleared up the issue and for some reason or another I can't get it to turn on anymore, and I noticed that the power switch was a little finicky sometimes and would require me to turn the power knob a couple of times before it would finally turn on, but now its not turning on at all period except for a little crackling noises when I would turn the power switch on and off several times and then turn it on and wait for it to warm up, but I'm not getting any audio.

I'm thinking its the power switch, because I have a Philco 116B that's done the same thing with its power knob, except instead of sticking in the off position like this one seems to be doing it sticks in the on position.

and the switch that this farm radio uses has 2 sets of contacts in it rather than one set like your traditional AC power switches, one set of contacts is for powering on the B+ power and one is for turning on the A+ (Filiment) power and I'm not sure where I would get a new switch like that or if I could take the switch apart and clean the contacts and lubricate them and see if I could get the switch freed up and working again.

And no its not the batteries because I just installed a set of freshly recharged "D" batteries in the "A" Battery pack and the "B" batteries are still putting out a solid 89.5 Volts DC.

Any help would be appreciated.

Thanks!

:thmbsp: Your next step should be to disconnect the A and B wires from the switch (with the batteries disconnected) and connect the A and B supply's wires together in the proper way that the switch connects them when it's on . Then reconnect the batteries . If the radio plays , your switch is bad . If not , your gonna be looking for other problems .

:thmbsp: Your next step should be to disconnect the A and B wires from the switch (with the batteries disconnected) and connect the A and B supply's wires together in the proper way that the switch connects them when it's on . Then reconnect the batteries . If the radio plays , your switch is bad . If not , your gonna be looking for other problems .

So how do I do that?

So how do I do that?

He explained everything except how to figure out which wires to bridge together. That you do either by looking at the schematic and tracing the wiring (which I recommend) or by checking switch terminal resistance with the switch on and off. (These methods should be fairly obvious to anyone who has been working on electronics for a while and knows how to read a schematic)

Personally I wouldn't bother disconnecting leads from the switch(though you could go through the extra effort if you want) unless the 2 poles of the switch that aren't supposed to have continuity are shorting.... what I'd do is either jumpper the contacts at the terminals with clip leads or tack solder jumper wires across the correct terminals.

He explained everything except how to figure out which wires to bridge together. That you do either by looking at the schematic and tracing the wiring (which I recommend) or by checking switch terminal resistance with the switch on and off. (These methods should be fairly obvious to anyone who has been working on electronics for a while and knows how to read a schematic)

Personally I wouldn't bother disconnecting leads from the switch(though you could go through the extra effort if you want) unless the 2 poles of the switch that aren't supposed to have continuity are shorting.... what I'd do is either jumpper the contacts at the terminals with clip leads or tack solder jumper wires across the correct terminals.

What I meant was do I connect wires together to bypass the switch altogether or do I connect the wires together and use the switch as well?

I guess I should of been clearer, but I was in a hurry last night.

What I meant was do I connect wires together to bypass the switch altogether or do I connect the wires together and use the switch as well?

I guess I should of been clearer, but I was in a hurry last night.

If you have shorted the wires into the on mode such that the set will be on regardless of the switch position as he suggested, then whether or not you use the effectively bypassed switch is irrelevant.

The idea is that the switch acting up and the reception issues could be unrelated or the former could be causing the latter...ie the switch could have resistance sufficient to reduce filament or B+ voltage that could potentially cause reception issues.

If you bypass the contacts with a short and run the set you will learn if it reception problems were caused by switch contacts developing resistance.

If you have shorted the wires into the on mode such that the set will be on regardless of the switch position as he suggested whether or not you use the effectively bypassed switch is irrelevant.

OK well I didn't understand that that was what he was saying.

But anyways I was just kind of monkeying around with the radio a little bit and I just turned the knob on just now and it came on just fine today on the first try which is weird because last night I couldn't get it to do anything.

I'll still try out what you said as far as trying to bridge the A and B wires together and see what that does.

but as far as which wires to bridge as I said if you look at the schematic and the switch wiring, it has four terminals on the switch, one is wired to the "A" Battery supply (Red Wire from the "A" Battery supply Pack) and the other one is wired to the "B" battery supply (the blue wire from the 10 9V batteries wired in series), and then the other two terminals are wired across the filiment string and the the B+ rail respectively, So I take it I would have to just put a jumper between the two "A" Supply switch terminals and the two "B" supply Terminals on the switch in order to bypass the switch?

See the schematic posted below.

...So I take it I would have to just put a jumper between the two "A" Supply switch terminals and the two "B" supply Terminals on the switch in order to bypass the switch?
Yuppers.:yes:

Yuppers.:yes:

Ok, that's what I was thinking but I wasn't sure, that's why I was asking.

OK so, an update: Its NOT the switch, its something else causing this thing to act up, because I took the switch apart on this radio and sprayed some WD40 into the switch and worked it around and checked the switch and it definitely opens and closes the circuit like its supposed to when the switch is in the on and off position.

So I put the switch back together and put the radio back together, and then let it sit for a little bit and then put the batteries back into the set and then turned it on and the radio came on like it was supposed to.

I listened to the radio for about 15 or 20 minutes and then suddenly the radio just died, it didn't fade out or slowly die it just immediately cut out with a slight "pop", almost like someone had turned the radio off with the power switch, but I hadn't touched it.

Any ideas as to what the problem could be?

Disregard previous post, I figured out what the problem was, it was a faulty 9V Battery in my "B" Battery setup.

Disregard previous post, I figured out what the problem was, it was a faulty 9V Battery in my "B" Battery setup.
I've been following this thread from the very beginning. I would knock together a simple B+ supply using a silicon rectifier or bridge rectifier, two 20mfd electrolytics , 2200ohm, 1 watt resistor and 180 ohm, 1 watt before the rectifier.
Once you get all the problems straightened out, you can go back to using battery power.
I built one 65 years ago because of the high cost of "B" batteries.
Flashlite cells were only 15 to 25 cents at the time. :scratch2:

I've been following this thread from the very beginning. I would knock together a simple B+ supply using a silicon rectifier or bridge rectifier, two 20mfd electrolytics , 2200ohm, 1 watt resistor and 180 ohm, 1 watt before the rectifier.
Once you get all the problems straightened out, you can go back to using battery power.
I built one 65 years ago because of the high cost of "B" batteries.
Flashlite cells were only 15 to 25 cents at the time. :scratch2:

I think what caused the faulty 9V battery in my "B" Supply was that I had taken this Radio over to my parents house last week to demonstrate the radio to them, and when I went to load the radio back into my car the "B" supply battery pack fell out of the back of my radio and landed on the ground which was covered in snow and I think that caused the battery to "short out".

Just goes to show that snow makes it more difficult to do most anything, with the possible exception of skiing down a hill. :D

Just goes to show that snow makes it more difficult to do most anything, with the possible exception of skiing down a hill. :D

Yep, I'd say so, because since I replaced that faulty 9V battery the radio has been working flawlessly since. :scratch2:

OK, so I have a question and a little update on this radio.

I was finally able to acquire a tube tester that can test the tubes that these old 1930s radios used, and I tested all of the tubes in this radio (except for two of them) and they all tested like brand new, and they are the original Coronado Branded tubes! :banana: :yes: :thmbsp:

Now for my question and the two tubes I was unable to test.

My Tube tester I have is a Knight Model 600 Tube Tester from the 1950s, and it had listed in its tube chart a 1A4P tube, but this radio uses a 1A4 tube, which from what I can see looking through the tube data sheets online they are basically the same tube, but then there are some tube data sheets that state that they are completely different tubes.

My tube tester results seem to confirm the latter idea, because when I used the setup data from my tube tester that is for a 1A4P to try and test my 1A4 tubes they get a mediocre reading and I know that can't be the case, because the rest of my tubes in my radio test like brand new (100+) and those 1A4 tubes couldn't both be the the same amount of deadness (40) and the rest be like brand new, and then have the radio working as well it does.

Anybody have any ideas as to why Knight would only list one 1A4 tube in their tester setup chart (the 1A4P) and whether or not there really is a difference between the 1A4 and the 1A4P tube?

Thanks for your help.

The 1A4-P is a pentode version of the 1A4, which is a tetrode (sometimes designated 1A4-T). This means that the P version has an additional grid, (suppressor grid), close to the plate to prevent secondary electron emission from the plate from landing on the screen grid. This improves the stability of the tube.

Since the secondary elections are repelled by the suppressor grid, and returned to the plate, plate current could be higher in the P version of the tube, which may account for differences in tube checker readings.

The additional grid in the P version is internally connected to the heater/cathode, so the tube base connections are the same.

jr

The 1A4-P is a pentode version of the 1A4, which is a tetrode (sometimes designated 1A4-T). This means that the P version has an additional grid, (suppressor grid), close to the plate to prevent secondary electron emission from the plate from landing on the screen grid. This improves the stability of the tube.

Since the secondary elections are repelled by the suppressor grid, and returned to the plate, plate current could be higher in the P version of the tube, which may account for differences in tube checker readings.

The additional grid in the P version is internally connected to the heater/cathode, so the tube base connections are the same.

jr

Ok, thanks for the explanation, so the 1A4s in my radio is probably fine then, especially since my radio is receiving quite well.

Ok, thanks for the explanation, so the 1A4s in my radio is probably fine then, especially since my radio is receiving quite well.

Back when I was first starting out in the hobby I had the same mentality; "The tube tester says it's bad so it's gotta be bad" even though it still worked fine in the radio. I eventually learned that it's how the tube performs in the radio, and not on the tube tester, that determines whether a tube is good or not. Tube testers sometimes lie, whereas a properly performing radio does not :thmbsp:

Back when I was first starting out in the hobby I had the same mentality; "The tube tester says it's bad so it's gotta be bad" even though it still worked fine in the radio. I eventually learned that it's how the tube performs in the radio, and not on the tube tester, that determines whether a tube is good or not. Tube testers sometimes lie, whereas a properly performing radio does not :thmbsp:

You are correct. Tube testers, even mutual-conductance testers, do not test vacuum tubes in so-called "real world" conditions, so they cannot be relied upon to provide reliable results. Replacement of a weak or outright defective tube with one known to be good has always been the best way to deal with tube problems. Tube testers are good, but they are not infallible. It is for this reason, again, that the best way to deal with a tube which a tube tester tells you is defective is to replace that tube with one you know is good.

OK, So I have a question about this radio:

Is it normal for a tube powered battery radio like this to drain the "B" Battery supply so that it goes from supplying 90VDC to the radio's B+ Circuit to a little over 50VDC to the B+ Circuit in the radio (which makes the radio barely operable) in less than 2 months?

I thought the "B" Battery supply was supposed to last almost two years with barely any use, and I'm using store brand 9V batteries like what was suggested by Radiotvphononut on one of his Youtube videos where repaired a similar radio to this and created a rigged up battery supply using modern 9V and "D" Cell Batteries.

Any Ideas as to what might cause this weird aforementioned issue?

OK, So I have a question about this radio:

Is it normal for a tube powered battery radio like this to drain the "B" Battery supply so that it goes from supplying 90VDC to the radio's B+ Circuit to a little over 50VDC to the B+ Circuit in the radio (which makes the radio barely operable) in less than 2 months?

I thought the "B" Battery supply was supposed to last almost two years with barely any use, and I'm using store brand 9V batteries like what was suggested by Radiotvphononut on one of his Youtube videos where repaired a similar radio to this and created a rigged up battery supply using modern 9V and "D" Cell Batteries.

Any Ideas as to what might cause this weird aforementioned issue?

Check your B+ current drain with the set on and off. If it draws current off something is wrong, if the on current is more than 20% higher than the sum of the max plate currents of the tubes data sheets then something is wrong....if the heaters are parallel wired you should be able to troubleshoot by pulling tubes one at a time and observing change in B+ current. The drop in current when a tube is pulled is what it's drawing, and if that exceeds what the data sheet says it should be then the circuit it's in is suspect. If all the tubes are out and its drawing substantial B+ current look for B+ shorts and resistive dividers off the B+.

Check your B+ current drain with the set on and off. If it draws current off something is wrong, if the on current is more than 20% higher than the sum of the max plate currents of the tubes data sheets then something is wrong....if the heaters are parallel wired you should be able to troubleshoot by pulling tubes one at a time and observing change in B+ current. The drop in current when a tube is pulled is what it's drawing, and if that exceeds what the data sheet says it should be then the circuit it's in is suspect. If all the tubes are out and its drawing substantial B+ current look for B+ shorts and resistive dividers off the B+.

Ok, well I know that this radio uses a 2 section power switch and I wonder if the switch section that switches the "B" supply could be stuck on and is causing B+ current draw when the radio power switch is switched off?

The radio was completely recapped so I know leaky caps aren't the cause.

I'll check the power switch and see if that's working correctly, although come to think of it this radio is almost always "instant-on" when I turn it on, which makes me wonder if the B+ isn't actually being switched off by the power switch like it's supposed to be.

Instant on in battery sets is typically a function of the extremely short warmup time of filament type battery tubes.

Instant on in battery sets is typically a function of the extremely short warmup time of filament type battery tubes.

Ok, so I'll just check a few other things then.

Ok, so I'll just check a few other things then.

Just disconnect the battery when not using it!
Batteries are expensive and when though showing it and how well it works, It isn't that difficult and it will give you piece of mind.

Just disconnect the battery when not using it!
Batteries are expensive and when though showing it and how well it works, It isn't that difficult and it will give you piece of mind.

Ok, well I didn't realize that the radio was still drawing current from the batteries even when its turned off, because I know modern transistor radios don't usually draw current from a battery when its turned off.

Is it normal for a tube powered battery radio like this to drain the "B" Battery supply so that it goes from supplying 90VDC to the radio's B+ Circuit to a little over 50VDC to the B+ Circuit in the radio (which makes the radio barely operable) in less than 2 months?

Two questions:

1. Approximately how many hours was the radio turned on during the two month time period ?

2. How much current does the radio draw when on and off ?

jr

Two questions:

1. Approximately how many hours was the radio turned on during the two month time period ?

2. How much current does the radio draw when on and off ?

jr

To answer question one, I've only used the radio maybe 3 times at the most in the two months that I've had it, and I usually only run it for a couple of hours to listen to some of my favorite talk shows in the evening and listen to a couple of oldies stations near me that play period correct music on it.

As for question number two the Riders says the radio is rated for 500 mA current draw (including tube filiments) and the current draw I measured was pretty close to that (around 495 mA).

So I guess I just need to follow Dave's Advice (Diesel Jeep) and just disconnect the batteries when not in use.

I should have been more specific... since we are concerned about the life of the “B” battery, how much current is drawn from the “B” battery when the radio is on and when it is off ? (MEASURE) An alkaline 9 volt battery is rated at about 550 mA hours.

For example, doing the math, if the radio draws 25 mA from the “B” battery at moderate volume, the battery would be worn out in about 20 hours of playing.

Is this the same “B” pack that fell into the snow last winter?

jr

I should have been more specific... since we are concerned about the life of the “B” battery, how much current is drawn from the “B” battery when the radio is on and when it is off ? (MEASURE) An alkaline 9 volt battery is rated at about 550 mA hours.

For example, doing the math, if the radio draws 25 mA from the “B” battery at moderate volume, the battery would be worn out in about 20 hours of playing.

Is this the same “B” pack that fell into the snow last winter?

jr

Yes it is, but I've since then installed all new batteries, that I had bought from Ace Hardware, because they had their house brand batteries on sale, that was about 3 months ago.

But I'm hoping that when I dropped those previous batteries in the snow that I didn't short something out, which is entirely possible. :scratch2::smoke: