Westinghouse LTV32w6 HD Need help to ID a component

[splitcrete]

Had the set hanging around I gets backlight but no picture or menu. I have read that they have bad T-Cons so I looked over the board and found a burnt to a crisp QP7 I have no number to go by I have a picture from SJ the same as mine but theirs has the part that burnt out on my board. Does any one know the number of this part?

[budm]

Re: Westinghouse LTV32w6 HD Need help to ID a component

Can you take the resistance readings of all 3 pins against the Ground trace (mounting hole copper plane)? 1= left pin, 2 = top pin, 3 = right pin.

[splitcrete]

Re: Westinghouse LTV32w6 HD Need help to ID a component

There is nothing left of it I was just a whitish powder. I tried to clean it and It just washed away.

[splitcrete]

Re: Westinghouse LTV32w6 HD Need help to ID a component

This is my t-con

[splitcrete]

Re: Westinghouse LTV32w6 HD Need help to ID a component

I hope a clear pic.

[budm]

Re: Westinghouse LTV32w6 HD Need help to ID a component

But there should be at least 3 solder pads, right? I can see at least two pads in the picture.

[splitcrete]

Re: Westinghouse LTV32w6 HD Need help to ID a component

top pin - 3.730 K ohm
left pin- 3.98 K ohm
right pin - M ohm climbed untill it reached O.L

[splitcrete]

Re: Westinghouse LTV32w6 HD Need help to ID a component

right pin started at 26.00 M ohm climbed to O.L

[budm]

Re: Westinghouse LTV32w6 HD Need help to ID a component

OK, at least none of the pins are connected to a dead shorted circuit that caused it to burn up like that. We need to find out next the function of this Transistor/MOSFET and how all these pins are connected to.

[splitcrete]

Re: Westinghouse LTV32w6 HD Need help to ID a component

I have my magnifier out ,and I will try to follow the pads.
I will draw a picture of what I find.

[splitcrete]

Re: Westinghouse LTV32w6 HD Need help to ID a component

I put a used t-con in,and I got a picture but then faded to black. Noise coming from speakers hi pitch squeal. I thought maybe bad caps on ps. I checked all the caps all ok I used an esr meter. I put the power board back in and now nothing. No volts coming out. Yes I did recheck my solder all good. Here are a couple pics.

[nomoresonys]

Re: Westinghouse LTV32w6 HD Need help to ID a component

hmm not even standby, did something maybe blow your power supply fuse?

[splitcrete]

Re: Westinghouse LTV32w6 HD Need help to ID a component

Fuse is good I have power at main caps,and bridge rec. No power on cold side of ps board.

[nomoresonys]

Re: Westinghouse LTV32w6 HD Need help to ID a component

maybe check the thread by ben3843100, I just bumped it, for easy location, good info there, even tho ben didn't FOLLOW UP.

[nomoresonys]

Re: Westinghouse LTV32w6 HD Need help to ID a component

https://www.badcaps.net/forum/showthread.php?t=13258 thats the thread.

[nomoresonys]

Re: Westinghouse LTV32w6 HD Need help to ID a component

A quick background on what happens at startup on these supplies. AC power is applied, the mains filter cap charges to full voltage (1.4 x line voltage). A low current path (bleeder resistor or constant current source in the SMPS controller) charges the Vcc filter cap to (usually) about 16V. At that point the SMPS controller starts.

The SMPS controller turns on the main power FET briefly, sending a surge of current through the primary if the transformer, causing pulses of current through the secondaries and a tertiary winding which provides Vcc for the SMPS controller. This is followed by additional pulses until the secondary voltage reaches the design value - usually 5 volts.

There are a few things that can stop this start-up cycle. If the Vcc filter cap is open, Vcc decays to below 10 volts and the process stops before the tertiary winding can provide enough voltage. An excessive load on the secondary will have the same effect. That can be a reversed cap, bad diodes, short on one of the loads, etc.

I'd have to see the part numbers of U2 and U4, but it appears to me that U4 is most likely the SMPS controller, mainly because of it's proximity to the opto-isolator.

PlainBill. Nice explanation of start up, post #28 of bens thread, Thanks Plain Bill.

[splitcrete]

Re: Westinghouse LTV32w6 HD Need help to ID a component

I just ordered a guaranteed power supply,and I will reverse engineer it to find the bad parts. Be back when it comes in.