PN58C590G4FXZA Won't turn on. Logic Board?

[johnboy1313]

This is my buddy's girlfriend's TV. I don't have any pictures. I'm looking for confirmation that my troubleshooting method is correct.

When plugged in, the red led on the front is solid. When trying to power on, it flashes a few times, there is a click from the PSU, and the led goes solid again. I unplugged each of the sustain boards one at a time with no change. I unplugged the logic board and the symptoms changed. The red led flashes and turns off as if the tv is powered on. The PSU seems to come up too without Vs. the Vs-on pin is part of the logic board circuit.

I also disconnected the LVDS cable from the main with the logic board plugged in and jumpered pins 3 and 4 on the logic board. There was no change in symptoms.

I believe the logic board is bad but it's possible that something in the Vs circuit is faulty on the PSU. Does the Vs-on pin go high at startup or is it pulled to ground?

Any thoughts?

[tw2005]

Re: PN58C590G4FXZA Won't turn on. Logic Board?

I think the problem with this approach is that the logic board would be part of the shutdown cct if a fault occurred on the sustains. Also , these later models from what I've read shutdown if the y or x are isolated.

fastrack attached

I think I'd be having a probe around the x, y and buffers for shorted components.

[johnboy1313]

Re: PN58C590G4FXZA Won't turn on. Logic Board?

Thanks, I will keep digging.

[tw2005]

Re: PN58C590G4FXZA Won't turn on. Logic Board?

Thanks, I will keep digging.

As you know I'm not a Samsung bloke but if the design is similar to the smaller models(certainly that fastrack reads similar) X-mains were an issue, at least for the 42" I looked at. Firmware update was available too. On that model it also appeared x takes out y and sometimes x,y and bufer needed doing.

I'm sure you'll work it out. Check the IGBTs for shorts

[johnboy1313]

Re: PN58C590G4FXZA Won't turn on. Logic Board?

Right on. Thanks for your help.

[johnboy1313]

Re: PN58C590G4FXZA Won't turn on. Logic Board?

I finally got a chance to get back to this one. With X and Y disconnected, Vs jumps to about 66V before the board shuts down. Va stays at zero. I suspect this is a bad PSU. I've gotta take a couple resistors over next time to try to force the PSU on.

[Toddm88]

Re: PN58C590G4FXZA Won't turn on. Logic Board?

Did you figure out what the problem was with this TV?
I'm working on a buddy's that is the same model and has the same problem.
Vs jumps up to about 55v while Va does nothing and then the power shuts off.

I replaced the QS802 and QS804 mosfets on the SMPS with no change.