westinghouse vr3215

[budm]

Re: westinghouse vr3215

I am looking for very low capacitance if the caps are bad something like less than 1uF. Did you measure them out off the board because the value is way too high for the cap that size?

[lookimback]

Re: westinghouse vr3215

I measured them in the board. Should I take them out? Also, do they have polarity? Several other SMD caps do say "open circuit or low capacitance" when I test them.

[budm]

Re: westinghouse vr3215

Just take one out, it is non-polarized cap. Do you consider buying the replacement board? One thing for sure is that if you monitor the 24v, it does stay around 24v or so and not dropping down to less than 20V?

[lookimback]

Re: westinghouse vr3215

I ordered a board from eBay this morning. $32. I'm still hoping to figure out what's wrong with this one and, if I fix it, sell it back on eBay. In any event, I'm learning a lot from this. I'll take out one of the caps and test both again.

[budm]

Re: westinghouse vr3215

I wish I can find the spec of that PWM IC, there is a 3-second timing pin controller that shutdown the circuit if there is the problem, if we defeat it then it will stay on for us to probe the voltages.

[lookimback]

Re: westinghouse vr3215

I spent about 2 hours last night looking for it. There's no other way to figure out which pin it is? C209 2.35uf, ESR 12 ohms. C210 2.37uf, 12 ohms.

[budm]

Re: westinghouse vr3215

The ESR is higher than I thought.

[lookimback]

Re: westinghouse vr3215

There's other caps around the PWM IC that I get "open circuit or low capacitance" message from

[lookimback]

Re: westinghouse vr3215

Caps in series with the PWM ic are as follows:
Some I can't get capacitance in-circuit.

Pin 1 ESR over 40
Pin 2 open circuit or low capacitance
Pin 3 2.03uf 12ohms
Pin 4 open circuit or low capacitance (reverse probes and it says ESR over 40 ohms.
Pin 5 no caps
Pin 6 2 caps 0.86uf, 1.10 ohms, cap 2 open circuit or low capacitance
Pin 7 open circuit or low capacitance
Pin 8 no caps
Pin 9 open circuit or low capacitance
Pin 10 no caps
Pin 11 no caps
Pin 12 open circuit or low capacitance
Pin 13 no caps
Pin 14 open circuit or low capacitance
Pin 15 0.78uf ESR 1.16 ohms (other side of cap connects to pin 6)
Pin 16 no caps

[lookimback]

Re: westinghouse vr3215

Just a long shot but I tried emailing the company that makes the PWM IC. Hopefully they can send me a data sheet.

[lookimback]

Re: westinghouse vr3215

I think these are the data sheets. 2 days looking and no luck then I search OB3328 PDF and find it on first page of search results.

[lookimback]

Re: westinghouse vr3215

I think I'm on to something. I have 6.87v on pin 11 (VDDA) and pin 15 (ENA). Data sheet says 7v between pin 11 and ground. So the chip gets power and is enabled. Pin 4 is voltage sensor (VS). If voltage above 3v is sensed, chip shuts down. Voltage on pin 4 is 2.7v. I removed the cap that is in series with VS pin and chip still shut down. I think the problem is with pin 1. Pin 1 (CS) is the lamp fail safe. "If voltage on CS pin is less than 350mv, the IC will initiate the striking timer. An internal constant 3.0ua current source starts to charge the capacitor connected to STIME pin. Voltage higher than 3.0v at STIME pin indicates an ignition timeout. Under such circumstances, PWM Gate outputs are disabled and thus power switches are turned off." Thats quoted from page 8 of the data sheet. Now, I have 6.75v on the STIME pin and 0v on the CS pin. That would indicate that the lamp fail safe circuitry is causing the shut down. So now I need to determine if all the CCFLs are good, then, if they are good, the problem will be in the CS circuit. I guess now, what I need to know, is how to safely test the lamps?

[lookimback]

Re: westinghouse vr3215

Well, I didn't have a way to test the lamps so I used different lamps to test the inverter. Different lamps didn't fully light either. Definitely the board that's bad.

[budm]

Re: westinghouse vr3215

It looks like you are going to have to spend the money on the new board at this point.

[lookimback]

Re: westinghouse vr3215

I ordered it already. I appreciate the help with this too. I'm going to compare values when the new board comes but I think I have it almost figured out. The data sheet was the key.

[budm]

Re: westinghouse vr3215

If the IC is cheap, then you can try replacing the IC. BTW, the application notes circuit just about matches my drawing as far as the MOSFETs and the transformers are connected. Pin 3 is the timer, if you tie that pin 3 to ground, it will keep on trying to fire the lamps up.
I have a feeling the circuit they using is copied from the application notes.

[lookimback]

Re: westinghouse vr3215

ok, im going to try that

[lookimback]

Re: westinghouse vr3215

New board came today. Works great. I'm still working on the old one. I've been swapping components between the boards. The PWM IC is good. I've swapped out the PWM IC, about 6 caps and one switching diode(was giving me different values than the one in the good board). All are part of the lamp fail safe circuit which connect to pin one (CS). I've got about 10 more caps in the circuit. Also compared values of every resistor, diode, transistor, etc. Values were all almost exactly the same as good board. It pretty much has to be a bad cap. I didn't compare values on the HV transformers yet. I'll do that first tomorrow. Right now I'm going to call it a night.

Edit: My new Fluke multimeter also came today. It puts the Radio Shack one I've been using to shame.

[lookimback]

Re: westinghouse vr3215

I got it. You will never believe what it was. There was a bent over terminal in one of the lamp connectors on the inverter board. I had swapped 19 SMD caps (most 1 at a time, then retesting), 1 switching diode and the PWM IC before finally getting it to stay on for a few seconds. During that few seconds it started to sizzle. I didn't realize right away what it was. I removed 4 more caps and tried them in the good board. These were the final 4 that were part of the lamp circuit. It was while I was soldering them in that I thought to check the terminals in all the connectors. The crazy thing is that the TV could never have worked with that terminal bent. I think the person I bought it from must have tried to fix it himself and bent the terminal. The only thing I've replaced on the TV is the electrolytic cap on the top of the board. I first put a temporary cap in just to see if it would work. Then last night I replaced that with a Panasonic FC. I just can't believe how simple it was.

This confirms what I had concluded from testing. It was the lamp fail safe protection causing the shutdown.

[budm]

Re: westinghouse vr3215

Thanks for feedback. Notes to myself: suggest to have ALL the connectors pins checked out also.