1949? Motorola 10VT24R, TS-14B chassis - Page 4 - Videokarma.org TV - Video

ZackN920 · #46 01-31-2017, 12:03 AM

Flickr huh, i'll give it a try later.

Guy's,... Suggestions???

Well, I changed out some bad resistors and got no change in operation, that I noticed. Probably more to go.

Anybody got a better copy of the schematic? The Sams i'm using from ETF is very blurry in some spots. For example, Looking at my print out compared to it on my pc, I got a wirewound resistor (R90) i'm confused about. On paper it looks like it's 2.5ohm, but on my pc with it zoomed in, it could be 7.5??? Since the one in place was real high, I put a 4ohm wirewound in that I happened to have on hand.

I could also use more voltage diagrams on some of the lines. For example, on C1. The original part is a 140mfd/150v cap. I measured it and voltage fluctuates from 148-151. That seems a little high to me, as I would figure manufacturer's wouldn't want to push there components that close to there maximum's.

Question about that part too. If C1 was bad, would that contribute/cause my pictures' wave? The new cap is a 150MFD/450V unit, and it actually gets warm?! With a voltage rating so much higher than nessisary, I wouldn't think it'd get warm.

bandersen · #47 01-31-2017, 09:28 AM

I don't see a Sams at the ETF. Do you mean the Motorola service manual ?

Yes, if that cap was defective I think you would have low B+ but probably not ripple. Make sure you have it installed with the correct polarity.

That cap is part of the B+ voltage doubler and has a fair amount of power going through it. Ideally, you want to use a low ESR type rated for high ripple current. That's more important than a high voltage rating in this application.

irext · #48 01-31-2017, 11:52 PM

That keystone looking raster may indicate a faulty yoke. Shorted turns in one of the vertical windings.

irext · #49 01-31-2017, 11:57 PM

Oops. Sorry. Should have read the whole thread. I see you've replaced the yoke.

ZackN920 · #50 02-02-2017, 12:24 PM

Quote:

Originally Posted by bandersen

I don't see a Sams at the ETF. Do you mean the Motorola service manual ?

Yes, if that cap was defective I think you would have low B+ but probably not ripple. Make sure you have it installed with the correct polarity.

That cap is part of the B+ voltage doubler and has a fair amount of power going through it. Ideally, you want to use a low ESR type rated for high ripple current. That's more important than a high voltage rating in this application.

It's kind of hard to find, you have to look for this model of TV. If you look for the chassis "TS-14B" they only have the service manual with it, and that schematic was just as hard to read as well

http://www.earlytelevision.org/pdf/M...-Sams-92-4.pdf

That cap is installed correctly. You say up above, that if the cap was bad I shouldn't have ripple(is that the technical term for a moving (still) image?). Yet below you mention that the cap should have low ESR(I don't know the specs when it comes to that) for high ripple current.
If that has high ripple current going through it, how would it not get past the cap, if the cap were bad?

Hey guy's, I found that I still have a few caps that look like wax paper caps, but are real low value. Lower than what I have for the standard replacements. 2 are in the tuner circuits and 1 is elsewhere. I'll get a pic up in a bit, but should these be replaced like normal value caps?
Could they be causing any of my current issues?

bandersen · #51 02-02-2017, 12:43 PM

C1 and C2A form a voltage doubler for the B+. They are constantly charging and discharging. See how C1 is going directly to the AC line ? All the B+ power for the set is pumped through that cap. That's why having a low ESR is important.

If either cap is bad, they would not fully charge up and B+ would drop.

It's the speaker field coil and C3A that are more responsible for filtering out B+ ripple.

ZackN920 · #52 02-02-2017, 01:08 PM

ah. Huh, well then my B+ sounds like it should be ok. It'd be nice if the schematic stated what its supposed to be...

Got the pics of those caps. They are listed as A. I also marked 2 other kinds that I'm unsure of. I've seen them before, but never really put much thought towards them and don't know whether to trust them or not.

bandersen · #53 02-02-2017, 02:00 PM

Didn't say your B+ was OK, just explaining how the power supply works. That cap shouldn't be getting warm.

That is a 7.5 ohm fusible resistor. They were commonly used to protect the selenium rectifiers from a surge on power up as well as act as a fuse for the B+. The value isn;t critial but you may want to increase it a bit if you replaced the seleniums with silicon diodes. Silicon is more efficient and will raise the B+.

While the Sams doesn't state the B+ right at C2, they do list many other voltages. If they are close, I'd say your B+ is OK.

Those are ceramic caps and rarely go bad. Don't mess with them.

mrjukebox160 · #54 02-02-2017, 11:40 PM

I read that you had the diodes in backwards at first. If C1 and/or C2A are getting warm I would change out the diodes just in case one was damaged with the high current draw from being backwards. I would start over with fresh caps and diodes. I would also check the field coil on the speaker for any short to ground or low resistance. I don't think the sams had an ohm reading for it maybe the original one does. If it has a partial short to itself it won't filter the B+ correctly and cause "hum bars" in the picture. How is the sound? if you can't get much volume out of it that could be a sign of a bad field coil.

ZackN920 · #55 02-05-2017, 09:51 PM

Quote:

Originally Posted by bandersen

Didn't say your B+ was OK, just explaining how the power supply works. That cap shouldn't be getting warm.

That is a 7.5 ohm fusible resistor. They were commonly used to protect the selenium rectifiers from a surge on power up as well as act as a fuse for the B+. The value isn;t critial but you may want to increase it a bit if you replaced the seleniums with silicon diodes. Silicon is more efficient and will raise the B+.

While the Sams doesn't state the B+ right at C2, they do list many other voltages. If they are close, I'd say your B+ is OK.

Those are ceramic caps and rarely go bad. Don't mess with them.

I was just figuring B+ should be around where its supposed to be. With how the set operates. I think I will swap that cap...again. This will be the 3rd time.
After I check some values at the tubes, i'll decide on whether or not to change that resistor's value. I'll probably go up to a 10ohm on it. Would it be good to find another fuseable resistor?
I'll leave them caps alone for now.

Quote:

Originally Posted by mrjukebox160

I read that you had the diodes in backwards at first. If C1 and/or C2A are getting warm I would change out the diodes just in case one was damaged with the high current draw from being backwards. I would start over with fresh caps and diodes. I would also check the field coil on the speaker for any short to ground or low resistance. I don't think the sams had an ohm reading for it maybe the original one does. If it has a partial short to itself it won't filter the B+ correctly and cause "hum bars" in the picture. How is the sound? if you can't get much volume out of it that could be a sign of a bad field coil.

No big deal to swap diodes, but they did test out good when I switched them the way they should be. hmm, I may have even changed them back then though...don't remember the best since that was about a year and a half ago.
Back when I blew the one cap, I changed out that other one that got warm. Ive also since, swapped some of the caps and simplified things, from how those previous pictures look.
The field coil is fine, no shorts in the speaker. Sound is great as long as the finetuning is set with the picture looking it's worst....

Well, I couldn't find my tube condition chart that I previously made when I started this. I knew I replaced a few tubes in the set, but what one's, I can not remember.

So, I went over all of them again and found some issues. First off, V5(3rd-vid-IF) had the wrong tube.

huh, don't know how I missed that. Could that cause one of my issues, particularly the sound issue? It had a 6AG5WA, when it should have another 6AU6. I also found V4 is shorted out on pins 5 and 7. I've got a bunch of 6AU6's on the way. Seems everything I come across that uses them, those tubes are usually weak.
Also found V9(AF.amp) is weak, so I got a 6J5GT on the way too.

Well, that's where I'm at so far. Haven't done too much with it the last few days. Been working on a number of other things.

ZackN920 · #56 02-11-2017, 08:56 PM

Well....I've now changed out those diodes and the cap that was warming up. Also changed R90 to 10ohm. That did lower B+ voltage a bit. don't remember numbers at the moment. I'm thinkin it was at 257v(or was it 157?...) coming out of the one diode, that then leads to the speaker's field coil.
Also swapped that wrong tube out. NO CHANGES in operation, and the new E-Cap I just put in warms up just like the last one! You cant tell me all these 150mfd/450v caps are bad?
I did check other voltages, but for whatever reason I didn't write them down. What I do remember is that they were off from what the schematic claims. I'm starting to think more and more that this schematic isn't for my set.