westinghouse vr3215

[lookimback]

Re: westinghouse vr3215

Yes, I have the 24vdc. Here's the pics. I took close ups of the back of the board so there are 5 pics. 1 front, 1 back, and then top third, middle third and bottom third of the back. This TV is the first one that was a real challenge. I've learned more from this one than all the others combined.

[budm]

Re: westinghouse vr3215

Thanks, I also found good pictures at SJ.
http://www.shopjimmy.com/catalogsear...nghouse+vr3215

So far it looks like the lamps are not getting the full voltage to drive the lamps completely. I will have to study the board to see how it works.

[lookimback]

Re: westinghouse vr3215

OK. The help is certainly appreciated. This one really had me stumped. Thanks.

[budm]

Re: westinghouse vr3215

Not sure if you have ESR meter to test that green electrolytic cap laying side way, I would replace that cap.

[lookimback]

Re: westinghouse vr3215

I ordered a Fluke 115 multimeter from eBay yesterday. Right now I don't have a way to test it. I bought a $20 ESR meter from amazon but it doesn't work. The Fluke works with up to 9999 uf caps. That should be good for TV repair. I don't have a green cap but I think you are talking about the blue electrolytic that is right in the center of the top side of the board. Am I correct?

[tom66]

Re: westinghouse vr3215

You can't use a capacitance meter to check most capacitors, as capacitors usually maintain their capacitance when they fail. It's their ESR that goes up.

[lookimback]

Re: westinghouse vr3215

Oh, I wish I would have known that sooner. Well, I can still use the Fluke for most other testing purposes. Can you recommend a good mid priced ESR meter please? Thank you.

[budm]

Re: westinghouse vr3215

"I don't have a green cap but I think you are talking about the blue electrolytic that is right in the center of the top side of the board. Am I correct?" Yes (it looks green to me, but my eyes are not that good anymore).

[lookimback]

Re: westinghouse vr3215

OK. Its a 35v 470uf. I'll replace it with a Panasonic FC. I think I'll order about a dozen since that cap is beginning to look like a very common cap on inverter boards. Thank you for the help. I'll let you know how it turns out.

[budm]

Re: westinghouse vr3215

OK, it is just a simple full bridge drive circuit driving the Inverter xformers primary side in parallel, since all the lamps are not getting full drive voltage, it has to be a fault in the common circuit some where. Can you get the P/N of that SMD PWM IC?
This is the simplified diagram, you should take the resistance reading between the Source and Drain pins of the 4 MOSFETs. C209, 210 should be check for resistance leakage and value (I do not know what the value is).

[lookimback]

Re: westinghouse vr3215

I'll post them when I get home tonight.

[lookimback]

Re: westinghouse vr3215

OK, sorry I took so long. The numbers on the SMD PWM are line one B13022, line two 0B3328UQP. Resistance readings on the MOSFETs are 10.01k, 41.9k, 39.1k, 9.99k. No way to check the caps right now. I'm going to look for an ESR meter on eBay right now.

[lookimback]

Re: westinghouse vr3215

OK the part number is OB3328UQP, not 0(zero)B3328UQP.

[budm]

Re: westinghouse vr3215

You can solder in another cap that you have, larger value is OK just to see if it makes any different.

[lookimback]

Re: westinghouse vr3215

I do have these that I ordered by mistake. They are 35v 470uf. I wouldn't leave them in but would they be OK just to test it?

[tom66]

Re: westinghouse vr3215

They should work for testing, but I would expect only a year or so before they fail.

[lookimback]

Re: westinghouse vr3215

If it works I'll order some FCs and replace them right away.

[lookimback]

Re: westinghouse vr3215

It didn't work. At least we eliminated that as a possibility. I did order a really good ESR meter from eBay. I'm sure that will help with future projects. I've been trying to find a data sheet for the SMD PWM IC, so I can try to figure out how to test it, no luck though.

[lookimback]

Re: westinghouse vr3215

So I did some live testing on the inverter board and think I made some valuable observations. 1, there is no power to the common side of the HV transformers. I think we already knew that though. 2, I have either positive or negative voltage on every terminal of the PWM IC, I don't know what those voltages should be but figure, since there are no terminals which are just nothing, that its probably working. 3, I have neither positive or negative voltages on either side of caps C209 and C210. 4, the big resistor on the top side of the board gets hot enough to burn you. This I found by chance when I was done and went to pick up the board. I hope some of this makes sense to someone reading this.

[budm]

Re: westinghouse vr3215

What is the value of that big resistor? It is hooked as a bleeding resistor (it is connected to the 24V+ and Ground) per my drawing. There will no DC across the primary side of both transformer due to the DC blocking caps, but there will be high frequency AC on the primary side.