Westinghouse LD-4285 stuck in stanby, short on mainboard?

[Ifixstuff9]

When the TV is plugged in the red standby LED comes on and nothing else... it won't respond to any of the buttons. I don't get any other signs of life from the TV.

I know that a few similar Westinghouse models had an issue where the backlight ribbon cables would short out against the LCD frame, but I have tried turning it on with the backlight ribbons disconnected and nothing changes. I also partially disassembled the panel to inspect the ribbons and they look fine, I even added some electrical tape to insulate them from the frame just to be safe.

This TV has just one board that handles everything, and power comes from an external 19v supply. I don't know much about board level repairs but I started by checking voltage regulators - only 3 of them had power, a MP2403DN and two 1117's. Here are the voltages:

MP2403DN (circled in red)
pin 1 = 9.8v
pin 2 = 19.46v
pin 3 = 5v
pin 4 = GND
pin 5 = 800mv
pin 6 = 1v
pin 7 = 7.6v
pin 8 = 3.6v

1117 (circled in green)
pin 1 = 444mv
pin 2 = 1.83v - fluctuates between 1.45 and 1.53 after about a minute
pin 3 = 4.9v

1117 (circled in blue)
pin 1 = 169mv
pin 2 = 292mv - shorted to ground
pin 3 = 4.93v

Looks like something is shorting out the last 1117. Not sure why the other 1117 starts off at 1.81v and then lowers to around 1.5v. Also, the main processor is hot to the touch and the tuner module is warm as well, I may be wrong but I don't think either of those should be warm when the set is in standby... at this point I'm not really sure what to do next. Are there any components that I should check for shorts?

[dick_barton]

Re: Westinghouse LD-4285 stuck in stanby, short on mainboard?

Can you lift the regulator (blue) and check if pad 2 is still shorted to ground?

[Diah]

Re: Westinghouse LD-4285 stuck in stanby, short on mainboard?

you need first to clean the boards complete with air pressure. and tell what are the label of U13. its sound the set at half boot.

[nomoresonys]

Re: Westinghouse LD-4285 stuck in stanby, short on mainboard?

Maybe try cooling or heating U13, power up see if there's any change, could also try heating the capacitors on the board with a hairdryer, see if there's any change, U13 there if it turns out to be the issue: https://www.ebay.com/itm/36332330489...cAAOSwefBgT0b1

[Ifixstuff9]

Re: Westinghouse LD-4285 stuck in stanby, short on mainboard?

Sorry for the delay, I finally got another chance to look at the board. I was able to remove the blue regulator and pad 2 is still shorted to ground. I also tried freezing U13, no change. Will try heating both U13 and the capacitors with a hairdryer later tonight and see if anything changes.

I also attached a pic of the label on U13 for Diah

[budm]

Re: Westinghouse LD-4285 stuck in stanby, short on mainboard?

The Blue regulator is the adjustable regulator IC, there should be filter caps connected to pin 2 of the IC, one will be MLCC (Multilayer Ceramic CAP) type connected in parallel with lytics type cap, so the short can be from shorted out MLCC or shorted load.
BTW, when you say shorts, how many Ohms is it? <1 Ohms?

[Ifixstuff9]

Re: Westinghouse LD-4285 stuck in stanby, short on mainboard?

The short I'm measuring is <1 ohms at about 0.56 ohms. Is the MLCC one of the three circled caps connected to the output of the blue regulator? I'm going to try removing all three and seeing if that changes anything

[RJARRRPCGP]

Re: Westinghouse LD-4285 stuck in stanby, short on mainboard?

When the TV is plugged in the red standby LED comes on and nothing else... it won't respond to any of the buttons. I don't get any other signs of life from the TV.

That's starkly familiar, expect it was a blue standby LED, with a TV that reportedly had a failure during a power problem, probably because of a nor'easter in eastern-Massachusetts.

It got brought up to Vermont and that's the type of symptoms I saw, (back in 2013, IIRC) then it got abandoned. (I wasn't even close to knowing how to possibly fix it, IMHO)



Looks like it will be known as "The Westinghouse nothing-except-for-standby-LED-syndrome". (IIRC, the brand was Westinghouse.)

https://www.badcaps.net/forum/showthread.php?t=42335