1950s RCA B & W TV
 

Hello everyone today I've been tasked with repairing a 1950s vintage 14" B & W TV for a neighbor and it works perfectly except for the vertical stage, the bottom of the screen is not all the way to the bottom of the screen, and the top of the screen is stretched so that people's heads look like they're larger they they really are. Any ideas as to what would be causing that issue? it has seperate vertical amp and output tubes, which I'm thinking one of them might be bad possibly, but not sure. Its a cold chassis set, with VHF Only. I have some pictures I'll post of the set.

You might get lucky and the tubes might make it a little better, but problems like that in an RCA are generally a capacitor problem. They're on the side mounted PC board. :sigh:

I noticed that it has only 7 paper caps on the PC Board and the rest are mylar type capacitors, and then on the back on the chassis (the metal part) theres several paper capacitors.

Even on their best day these RCA's don't have the best vertical, bad capacitors, drifted resistors and probably a rotted yoke cover just make it all the worse.

Vertical recap including/especially the output cathode lytic seems necessary. When I fix an RCA of that era for someone I don't let it leave my bench without a full recap (cause I know I'll get a call back when a vintage cap soon lets go).

I had a similar looking, but series string version of the set, and it did not use a cap in the cathode circuit of the 6AQ5 vertical output tube (cath was grounded). The problem cap was a .022 uf cap connected to the grid of the vertical output... I went ahead and changed all of the caps in the vertical circuit anyway. Somewhat difficult to get the pc board out, IIRC, think I "j hooked" the caps.

jr

Alright I'll see what I can do. it doesn't help matters that some of the capacitors on the PC Board are of the "Bumblebee" Variety which means I'm gonna have to figure out what the stripe patterns mean on each of the capacitors. :sigh: The rest of the capacitors have the value written on the case so I'll have no problems there.

Ever see a modern replacement cap with a 3 digit value referenced to pF? For instance a 332k cap is 3300pF=.0033uF or a 104k cap is .1uF=10,000pF. Bumblebees use that same modern notation only the numbers are encoded in resistor color code (there are also usually extra bands for tolerance and voltage)....IMHO if you are using modern caps with that notation and know color code, bees are easier to change than other styles since you can read the number off the color code and then grab that number out of the replacement parts bin.

This might help:

https://imgv2-2-f.scribdassets.com/i...471/1455831005

jr

Now what's interesting about these Bumblebee caps is that they are of the radial leaded type that sit upright on the board as opposed to the axial leaded type that you normally see.

Thanks for the link, that was very helpful. :yes: :thmbsp:

I've seen and replaced both. They both have the same color coding scheme.

OK, well that's good to know because this is the first time I've ever come across a radial leaded Bumblebee capacitor, I've seen the axial leaded ones plenty of times before in old radios but never a radial leaded one.

You can still use the axial caps to replace them, just bend one lead over so they both stick out the same end and stick it on the board.

You have to remove the metal shield from the bottom of the board to do the soldering, it's not all that hard, five or six screws around the edge, possibly a trimmer cap soldered to the shield and the shield soldered to the board in three or four places, a lot of stuff but not hard to get to. It's actually a bit more difficult to figure out how to maneuver the shield out around the wires.

As I mentioned, the vertical on these is pretty fussy so check all the resistors in the vertical circuit and replace any that are more than 10% off. Use care with the soldering iron, the traces on the board are flimsy and will peel off easily if they get to hot (or even if they don't).

I just finished up a similar set but series string and 17" tube, I never did get the vertical perfect, just good enough that you don't notice any imperfections unless you have a test pattern on.

Yeah, I kind of figured as much about the circuit traces being easily lifted, as it was the same way with my 1957 GE 9" TV, when I went to replace the capacitors on the PC Board on that TV a couple of the Circuit traces lifted at the holes where the capacitors go through and attach to the board, thankfully they stayed attached to the board well enough to keep the circuit intact, I'm guessing that since this TV uses a seperate tube for the Vertical amplifer stage vs. the Vertical output stage, that means that the vertical circuit capacitors are going to be in two different areas of the board?

Amazed it still works at all given the age of those caps... Also amazed that anybody outside of a TV collector would be interested in it.

Oh trust me, my neighbor is into all kinds of vintage stuff, He has an old Setchell Carlson TV/Radio/Record player combo unit that he had restored by someone in Ohio (I think it was the same person as mentioned on here several times), he has several old radios and he restores antique cars, and he has LOTS of Mid-Century Modern Furnature, and he lives in a perfectly preserved mid-century modern house that was his parents place originally.

OK, So, a little update, I started compiling a list of capacitors I need to redo this set and while I was in the process of seperating the chassis from the picture tube I accidentally damaged the original speaker, which just so happens to be a permanant Magnet type speaker similar to what you would find in any modern clock radio, so it looks like I'm gonna have to cannibalize an old clock radio for a speaker for the TV, what's weird though about the original speaker in this TV is that it was being powered by only one wire, the side that would normally be the negative lead had the wire coming off of the voice coil and into the connection terminal block and grounded the negative voicecoil wire lead to the speaker chassis. Has anyone ever seen this done before? I haven't and I find it rather unusual and I don't think its going to be possible to replicate that in a modern speaker because usually the voicecoil wire is snipped off right at the soldering lug for the voicecoil wire on the terminal block for the speaker and so it wouldn't be possible to ground the voicecoil wire to the speaker chassis unless I were to take a wire and jumper it off of the voicecoil wire connection and to the speaker chassis (or in this case the rivet that holds the speaker connection terminal block to the speaker chassis.)
Anyways It seems that the high voltage section of the TV (the back side of the metal portion of the chassis that the High Voltage Rectifier tube, Damper Tube and the Rectifier tubes are attached at) has about 10 wax paper capacitors of which about half of them look a little toasty like they had gotten a little too hot somehow, and showed signs of the wax coating on the outside of the capacitors getting charred or burned somehow, and even some of the resistors near those toasty looking capacitors looked a little toasty as well (but they were only 1/2 watt resistors so the resistors couldn't of gotten too hot themselves unless they shorted.) Any ideas as to how or why these paper capacitors got toasty looking like they did?

Small to moderate tears in speaker cones can be fixed with glue.

This isn't speaker cone damage, its the actual terminal strip on the back of the speaker where the electrical connections for the speaker hook to on the back of the speaker that broke and broke the wire coming off of the voice coil with it.

See picture below.

Well if the wire from the voice coil is still intact you can glue the strip back on and reconnect it.
If it pulled off at the cone of the speaker you may still be able to reconnect it and glue it back in the cone. Otherwise you need a new speaker, shouldn't be too hard to find one.

Well I'm gonna just need a new speaker because while the voicecoil wire is still intact in the cone the wire broke off of the terminal strip to the point that I couldn't get it reconnected even if I tried because there's nothing for me to grab onto.

Now as for trying to get a new speaker that's wired for two wires to work in a circuit that only requires one wire for the speaker to work, that's going to be the tricky part.

UPDATE: I've got the capacitors for this TV on order and they should arrive by either Monday or Tuesday. Surprisingly enough most of the capacitors in this TV were fairly common values, except for 3 of them, a .39 MFD, a .039 MFD and a .056 MFD capacitor (of which the .056 MFD was one of the bumblebee caps) so I ordered the closest value I could get to those values the .39 MFD I ordered a .33 MFD and the .039 I ordered a .033 MFD and the .056 MFD I ordered a .047 MFD.

So hopefully this TV will work properly once I recap it, seeing as it was already 80% working when I first got it from my neighbor.

Also One thing I found interesting is that the yoke was still in really good shape yet on this TV it wasn't cracked or broken or anything.

It's a normal speaker, one side is just hooked to chassis ground.

The way they did the original speaker was that they took the wire that came off the voicecoil and soldered it to the rivet in the center of the connection terminal strip for the negative connection, and since most of the speakers that are similar to the original one that I'll find in a vintage alarm clock radio from the 1980s will have the wires from the voicecoil just connected to the terminal connector, would it work if I just used a small length of wire and jumper between the negative terminal voicecoil connection and to the terminal strip rivet in the middle of the terminal strip that's holding the terminal strip to the speaker chassis?

Yes, or any other convenient point on the metal speaker frame.

jr

OK, and seeing as I have a stash of about 6 1980s vintage clock radios that use a similar style speaker to what I need, I shouldn't have any issues sourcing a speaker, seeing as 2 of the 6 clock radios have a really bad tuner in them that can barely pick anything up, I may just use one of those.

UPDATE: I completely recapped this TV except for 2 capacitors on the PC Board which I couldn't get to because I couldn't figure out how to remove the PC Board completely without damaging anything plus my soldering iron wasn't hot enough to remove the solder off the edges of the PC board to remove it from the back. Anyways the TV still seems to have a vertical problem even with 98% of the capacitors replaced. Any other ideas as to what could be wrong with this TV besides capacitors or tubes? The funny thing is that this TV doesn't seem to have a Height adjustment which is what this TV is acting like its needing an adjustment with.

It should have a height adjustment, usually one of the controls on the back edge that doesn't have an extender on it.

You don't need (or want) to remove the PC board, just the metal shield that's covering the back of it, that is held on by several screws around the outside edge and several tabs that are soldered to the board.

If the Caps you couldn't replace are in the vertical circuit then they are probably causing the problem. Those sets are difficult to get good vertical adjustment on their best day, anything out of spec will only make it worse.

Some of those odd caps like the .0039 and the .056 are 10% tolerance so if you replaced them with .033 and .047 it could also be affecting it.

Check the resistors in the vertical circuits, they are pretty critical.

If this is the model that uses a 6AQ5 for the Vertical output try swapping it with the 6AQ5 in the Audio and see if it changes anything.

This chart shows where the vertical controls are, I don't think this is exactly the right schematic but those controls should be the same.

Also make sure you have the picture centered with the centering magnets on the yoke, trying to compensate for an off center picture with the height and linearity will complicate things terribly.

http://videokarma.org/attachment.php...1&d=1458779873

Thanks, The .39 and .039 MFD capacitors I did replace with .33 and .033 MFD capacitors and the .056 MFD Capacitor was replaced with a .047 MFD capacitor because I couldn't find anything that came close enough in value (seeing as those values are from the old value system) Also I did accidentally get the yoke put on wrong so that the picture was off kilter slightly (the picture looked like a diamond instead of a rectangle) so I fixed that. As I said before I did try to take the shield of the back of the circuit board but my soldering iron wasn't getting hot enough to melt the solder blobs holding the shield to the board, most of the capacitors on the board I was able to fudge with slightly because I just moved the top cover of the shielding back slightly just enough to get my soldering iron into the back and removed the majority of the capacitors out that way without having to completely remove the shielding, although in the process of removing some of the capacitors I did accidentally lift some traces but I was able to bridge them using some wire (like I've seen done on here before by others.)

UPDATE: Figured out the that the height adjustment was off so readjusted that and now I have a full screen again. Now I have another issue though and its with the tuner, it seems that anything with an RF Output that I hookup to the TV using Channel 3 or 4 the station using channel 3 shows up on channel 2 and three and when using channel 4 it shows up on channel 3 and channel 4 and for some reason or another I can't seem to get the channel to lock in properly when fine tuning it and it makes lots of buzzing noises in certain screen lighting conditions. I was thinking that maybe I need to replace the tubes in the tuner but I'm not sure, any ideas as to what could be causing my tuner issues?

Just FYI, 0.39 and 0.56 are still currently made values, I would suggest not substituting values of caps in TVs because some of them are quite critical.

RCA, always seemed to be into those odd-value caps.
When I first started repairing, the parts houses didn't seem to carry those values.
The RCA distributor was miles from my place. Half the time, they didn't even stock them! :thumbsdn:

Yeah when I needed a 0.056 I just paralleled a 0.047 with a 0.01... That's well within the +-10% spec

If that's the case then how's come none of the parts suppliers that I usually go to (like AES or Parts Express or some of those other places that carry capacitors) don't carry those values? I've even looked at places like Mouser and Digikey and they didn't even carry those values, anything beyond the standard values are considered a special order item with them which can take weeks or months to get in depending on the backlog.

Not just RCA but GE as well because I know that my GE 9T001 Television had 1 .0039 MFD capacitor in it and I had subbed it out for a .0047 MFD capacitor (which thinking upon it now probably a .0033 MFD probably would of been a little closer to the original value than the .0047 would of been.)
Anyways what is up with these oddball capacitor values in these vintage TVs? Why couldn't of they just used standard values for everything instead of using all standard values except for a couple?

Possibly the engineers of your TV were fussy and wanted the perfect size no matter the oddity???

When I recently recapped my RCA, I think Just Radios had many of the caps, Capacitor world some of the others, and 1 high volt cap I got off ebay. There was an odd 5% cap that cost a buck, but JR had it. Ive slowly been building up my inventory, and always buy an extra of each size I order as I'm sure I'll need another sometime. It does save special orders. Its the initial buying that costs money. Good luck!