Westinghouse SK-26H240S Power supply issue

[102mm]

Need some help with this one..
Picked up a Westinghouse SK-26H240S that powers on with the just power light only.. No display or sound.

Main cap reads 172V and does not change at power on. I started checking the IC's on the board but i am unsure of what voltage needs to be where.. I know i get my 5V STBY, and i get 3.5V power on but from there i am lost.. which area should i be looking in? The P/Ns for the ICs are below. Thanks in advance.

U1- L6562D
U801 - P1027-65
U101 - TEA1610T
U702 - AS393M

[awyatt2]

Re: Westinghouse SK-26H240S Power supply issue

have you tested the esr on the startup cap?usually 10,22, 47 uf at around 16v or so,find it and try heating it up with a hairdryer to lower the esr and see if it will start.

[manstoblame]

Re: Westinghouse SK-26H240S Power supply issue

okay note that I am no authority on the subject but check the instructions on lcd tv repair facts here sure you'll find some helpful info there from my own experience I would begin by checking all outputs from the power board at the pin connectors and make sure you have voltages needed to power on the backlights. And while attempting any electronic repairs please use safety first these sets can kill!!!! my thinking is that it could be something as simple as a capacitor or opto sensor or voltage regulator you will need schematics and the like to find area's to check for shortages just my 2 cents

[CapLeaker]

Re: Westinghouse SK-26H240S Power supply issue

Stby voltage is there. Next you need to check if the main board is sending PSon (power on) and BLon (backlight on) back to the PSU, while you try to turn on the TV. If that isn't there, you have a main board problem.

[102mm]

Re: Westinghouse SK-26H240S Power supply issue

Stby voltage is there. Next you need to check if the main board is sending PSon (power on) and BLon (backlight on) back to the PSU, while you try to turn on the TV. If that isn't there, you have a main board problem.

I have the PS_ON signal, 3.9V that appears when i push the power button. the power supply does not identify the pins on the connector, it's a tough one.

[awyatt2]

Re: Westinghouse SK-26H240S Power supply issue

if the main cap dosent increase in voltage whenit is started the power supply is not starting. try what I told you. look for a 10 to 47uf at 16v cap and heat that area it will lower the esr letting it start. it may be a main problem but look at the simple first.i have fixed a large number of sets with this until I got my esr meter.

[102mm]

Re: Westinghouse SK-26H240S Power supply issue

if the main cap dosent increase in voltage whenit is started the power supply is not starting. try what I told you. look for a 10 to 47uf at 16v cap and heat that area it will lower the esr letting it start. it may be a main problem but look at the simple first.i have fixed a large number of sets with this until I got my esr meter.

You mean the smaller cap beside the Filter cap?.. I tried the heat with no luck. That's correct, The P/S isn't starting.

[CapLeaker]

Re: Westinghouse SK-26H240S Power supply issue

You mean the smaller cap beside the Filter cap?.. I tried the heat with no luck. That's correct, The P/S isn't starting.

No, he meant the big main filter cap on the primary. just be careful around the primary as you are connected to the mains.

[102mm]

Re: Westinghouse SK-26H240S Power supply issue

I have checked the main filter cap and the smaller cap beside it. Heating it does not work, the filter cap stays at 172V at at STBY and power on. The main board does respond to to power on since the indicator light comes on and it's supplying the 3.9V back to the P/S, but the voltage at the filter cap does not change and i get no 24V out.

[budm]

Re: Westinghouse SK-26H240S Power supply issue

You have PS-ON signal but the DCV on the main cap does not go up to >360VDC, then you have problem with the PFC Voltage booster circuit, the 24V power supply requires that boosted Voltage to work.

[102mm]

Re: Westinghouse SK-26H240S Power supply issue

You have PS-ON signal but the DCV on the main cap does not go up to >360VDC, then you have problem with the PFC Voltage booster circuit, the 24V power supply requires that boosted Voltage to work.

Thank you.. so the question is what are the voltages that require that circuit to work.. The PFC is L6562D, Should i just replace that or could it be other components in the circuit.
I'm really trying to learn these power supplies. but they are proving to be very difficult even on the cheapest TVs.

[awyatt2]

Re: Westinghouse SK-26H240S Power supply issue

no there is a smaller cap 10 to 47uf probally 16 t0 25volt called a startup cap, I don't have the schematics to tell you the number. heat any smaller caps and try again the large one is the main cap you are looking for the startup cap a lot smaller in size.

[CapLeaker]

Re: Westinghouse SK-26H240S Power supply issue

Have a look the mosfet and the gate drive circuit on the PFC