Westinghouse VR-3710 stuck in standby

[isherwood]

This set gradually stopped powering on past standby. For a while it would come on with repeated attempts.

Also, for most of the life of the set (2-3 years) it made a high-pitched whine during operation.

The board is an AY116L-4HF01. I suspect bad caps, but there's no visual indication of them. I'm hoping someone can recommend some to change out, or some other course of action. Thanks!

[dick_barton]

Re: Westinghouse VR-3710 stuck in standby

Disconnect the mainboard from the power supply. Do you have +5VSB. If so connect a 1K resistor from +5VSB to PS_ON and check you have the +12V, +5V & +24V voltages.
Also check what DC voltage you have across the two legs of C31 at that time.

[Andrew F. Ali]

Re: Westinghouse VR-3710 stuck in standby

Seems to me e-caps on the Main Bd may need replacing. Check the PSU as dick barton suggested....but is that 6VSB stand-by I see on the label??

[isherwood]

Re: Westinghouse VR-3710 stuck in standby

Thanks for the responses. I was able to verify 5v standby, but I'll need to procure some jumpers and the correct resistor to continue troubleshooting. Unfortunately Radio Shack returned to their roots as a parts house, but then they promptly closed both stores in my community.

[isherwood]

Re: Westinghouse VR-3710 stuck in standby

All right, I've received my goodies and did as you suggested, dick_barton. Here are my results:

5v: 4.98v (both pins)
12v: 11.54v (both pins)
24v: initial reading of ~18v, which dropped to nothing almost immediately, then ~11v to nothing, then zilch
C31: initial reading ~18v, then nothing

For what it's worth, I'm familiar with basic electronics theory and the common components, but I'm not versed in troubleshooting technique.

Thanks again for your assistance.

[dick_barton]

Re: Westinghouse VR-3710 stuck in standby

Place your meter leads on each pin of C31. The voltage is high so be careful. Set your meter to DC volts with black lead on -ve pin of capacitor and red on +ve pin of capacitor.

So just to confirm that all your voltages come up and are steady except for the 24V supply which initially comes up at approximately 18V DC and then drops towards 0V.

[dick_barton]

Re: Westinghouse VR-3710 stuck in standby

With the set off check the diode with your meter set to diode mode.

[isherwood]

Re: Westinghouse VR-3710 stuck in standby

Right, the 5v and 12v pins maintained constant readings.

C31 reads 381v.

I did some reading on testing diodes, but I have low confidence in my results. One direction reads 001, and the other reads higher, up to around 020. It seemed to climb as I was testing. Help with that would be appreciated. I'm not sure which capacitors may need to be discharged.

[dick_barton]

Re: Westinghouse VR-3710 stuck in standby

With the set disconnected unsolder one end of the diode (or both, up to you) and lift up off the board and measure the diode with your meter set to diode mode. Should be around 0.6 - 0.3 one way and OL (no reading) when you swap your leads.

[isherwood]

Re: Westinghouse VR-3710 stuck in standby

I desoldered one end and had it lifted completely free. In forward-bias direction I got 002, and in the other it started at around 200 and climbed steadily. When I gave up after about 20 seconds it was over 1300.

This is my meter, for what it's worth.

[dick_barton]

Re: Westinghouse VR-3710 stuck in standby

What have you set your meter to Ohms, Kohms, Diode????

[dskall]

Re: Westinghouse VR-3710 stuck in standby

With the set disconnected unsolder one end of the diode (or both, up to you) and lift up off the board and measure the diode with your meter set to diode mode. Should be around 0.6 - 0.3 one way and OL (no reading) when you swap your leads.

If you have continuity/diode mode on your DMM you should get readings above
C31 is the cap that needs to be discharged.

[isherwood]

Re: Westinghouse VR-3710 stuck in standby

I'm in diode mode (5:30 position on my meter).

Would I need to discharge the cap if I have one leg disconnected? What size resistor is appropriate? (I have 1/4w resistors on hand.)

[dick_barton]

Re: Westinghouse VR-3710 stuck in standby

What is the part number of the diode as written on it.
If you tested in diode mode it should only have read in one direction and not the other when using the meter probes.
It will read though if you have your fingers on the probes when testing.

It looks at the moment like a faulty diode.

[dskall]

Re: Westinghouse VR-3710 stuck in standby

Always make sure main cap is discharged power unplugged before working on board.
Measure voltage across main cap. Most will discharge after a few minutes. You would need several watt resistor to discharge.

[isherwood]

Re: Westinghouse VR-3710 stuck in standby

I completely desoldered it to remove any doubt about stray voltage, and I was sure to test in isolation of my fingers.

Forward: 0
Reverse: perpetually rising from about 200 (which may mean 2.00v--not sure)

Diode: MIC SR560

[isherwood]

Re: Westinghouse VR-3710 stuck in standby

Thanks, dskall. Main cap reads 0 at this point (board completely disconnected).

[dick_barton]

Re: Westinghouse VR-3710 stuck in standby

I would replace it. It's a 60 volt, 5 Amp Schottky diode. [SR560]

https://cdn.badcaps-static.com/pdfs/...453c4de773.pdf

[dskall]

Re: Westinghouse VR-3710 stuck in standby

Odd reading

[isherwood]

Re: Westinghouse VR-3710 stuck in standby

Thank you. Might that resolve my issue, or is it likely a symptom of a larger problem?