RCA 32V432T Possibly Bad Fly-Back Transformer?

[Spork Schivago]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

I think I found another one!!! I went back through the ones in the vertical out circuitry. The ones that read real high for the capacitance and found a 10μF cap (C303) having an ESR of 28.8Ω. I know the lower caps have higher ESR values but isn't that too high?

[Mrx3750]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

Don't even bother testing in circuit as you will get unreliable results.

Pull out of circuit, test, replace if tests bad. I would think an ESR higher then a few ohms is bad.

[redwire]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

All IC301's pin DC voltages look good except pin 6 looks measured wrong; it should be around +14VDC, not -1.2VDC (unless D301 is faulty).... still, I would change C302... and other electrolytics around IC301.

[Spork Schivago]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

All IC301's pin DC voltages look good except pin 6 looks measured wrong; it should be around +14VDC, not -1.2VDC (unless D301 is faulty).... still, I would change C302... and other electrolytics around IC301.

Doesn't C251 (the first bad one) feed into pin 6? I bet now that I replaced C251 with a good cap, that pin will test good. Correct me if I'm wrong. I also found a 10μF cap in some old boards that tested okay. I'm going to replace C303 with it. I cannot find one at the local radio shack. In this area, Radio Shack is the only place I know of that sells stuff like this and they have a fairly small selection. I have to order most stuff off the net. I'll let you guys know if replacing C303 fixes it and if not, I'll pull the other ones by IC301 and check them out of circuit.

[Spork Schivago]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

All IC301's pin DC voltages look good except pin 6 looks measured wrong; it should be around +14VDC, not -1.2VDC (unless D301 is faulty).... still, I would change C302... and other electrolytics around IC301.

D301 tests infinite one way and the other it tests around 12 MegaOhms. Does that make it bad? I'm waiting on a 100μF from Radio Shack for C302. I got it removed. I will replace it.

[Mrx3750]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

D301 tests infinite one way and the other it tests around 12 MegaOhms. Does that make it bad? I'm waiting on a 100μF from Radio Shack for C302. I got it removed. I will replace it.

Are you testing it out of circuit?

[Ltank]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

Have you checked the frequency of the vertical oscillator circuit. Looks like a double fold over. Looks like its at lease 120 Hz not 60.

[Ltank]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

Horizontal output transformer supplies scan left to right 262 fields of even and odd. It also provides scan rectification for other power supply voltages. Vertical freg has to be 60 Hz for top to bottom scan
As the horizontal is 1750 Hz left to right. 30 years ago I worked on Crt type sets then did industrial electronics.

[Spork Schivago]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

Have you checked the frequency of the vertical oscillator circuit. Looks like a double fold over. Looks like its at lease 120 Hz not 60.

I have not. It seems to me like you're talking Japanese. My multimeter has a setting for Hz. If I set it to that and put it in one of the house outlets, it reads around 120. Would that be the setting I'd want to check the frequency of the vertical oscillator circuit? Also, how would I test it? Is there an IC or something?

[Spork Schivago]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

Are you testing it out of circuit?

No, I will do that now. I also replaced C302. Didn't fix the problem.

[Spork Schivago]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

Are you testing it out of circuit?

Hey! I pulled it out and tested D301 and it reads OL (infinite) either way I test it. If I put the COM probe on the cathode side, and the Ω probe on the anode side, it reads OL. If I switch them around, it still reads OL. That means it's open (bad), right? When the positive probe is on the anode and the negative on the cathode, I should get a reading, right?

It's a 1N4001. Would this one work? http://www.radioshack.com/product/in...ductId=2036268

Thanks everyone! I have a great feeling about this! I think this will probably fix it! I removed all the caps by the vert. out IC and tested them. I even replaced a few. This should do it, I hope! I'll wait on your guy's response to see if that one at radio shack will work as a replacement or not. Thanks again!

[Spork Schivago]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

Are these diodes supposed to test high? I have another one, never used, and I test it, one way reads around 4 Mohms and the other way, infinite.

[tom66]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

That's bad for a 1N4001, but it's very rare for them to fail open like that. They most often fail short.

[Spork Schivago]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

Attached are new pics of the screen, almost perfect! With the diode that I put in, the 4Mohm one, could it cause these problems now? The screen is a bit crooked and it doesn't fill the screen all the way. Almost all the way, but not quite.

[tom66]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

The engineer put the diode in for a reason, and it's a $0.01 part, I'd replace it anyway.

[Th3_uN1Qu3]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

You can replace 1N4001 with any 1N400x. The fault you are seeing now is due to a different part of the circuit IMO, but doesn't hurt to replace the diode again with one that tests good (on diode scale, should read open on ohms unless you're accidentally touching both leads with your fingers).

If the problem persists, check all voltages according to schematic, especially B+ and vertical amplifier. The power supply is low somewhere. Likely more bad caps.

[Mrx3750]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

Attached are new pics of the screen, almost perfect! With the diode that I put in, the 4Mohm one, could it cause these problems now? The screen is a bit crooked and it doesn't fill the screen all the way. Almost all the way, but not quite.

Oh yeah you're on the right track.

Are you sure the TV is getting a 4:3 signal? That looks like a 16:9 image, and I don't see squashing.

As for the crooked screen, that lies in the yoke position, and with it being an RCA, the yoke is likely bonded to the CRT.

[Spork Schivago]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

You can replace 1N4001 with any 1N400x. The fault you are seeing now is due to a different part of the circuit IMO, but doesn't hurt to replace the diode again with one that tests good (on diode scale, should read open on ohms unless you're accidentally touching both leads with your fingers).

If the problem persists, check all voltages according to schematic, especially B+ and vertical amplifier. The power supply is low somewhere. Likely more bad caps.

I bought a new 1N4001 and am about to put it in. I've only replaced caps and one diode and all the caps I replaced were rated at the same voltage / microfarads as the bad ones. The new diode reads about the same as the one I put in earlier. To my knowledge, this TV has never been worked on. I don't think there's any different parts in the circuit.

As for the B+ and the vertical amplifier, how do I tell what the B+ and the vertical amplifier is? I really appreciate everyone's help. I don't know much about this stuff and I am trying to learn as I go. There seems to be a little bit of a learning curve. I can test components and replace them but understanding why things work or how they work, that's where I have trouble.

[Spork Schivago]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

Disregard the first part of that post. I misunderstood what you were saying.

[Mrx3750]

Re: RCA 32V432T Possibly Bad Fly-Back Transformer?

I think your TV is basically fixed judging from the last images you posted. I think your issue with the image not filling the screen is because the signal you're feeding it a 16:9 letterboxed image.