Sony fwd 42pv1 dont turn on.

[danielsoy]

Dear ppl, i need help to know if this KNP 4840 Power supply from a
sony fwd 42pv1 plasma monitor is workig or not.

Here is the full story short:
When I got this plasma, there was no image on the screen, but the red stand by led
turned to green and started to blink 5 times, and i could hear its two relays clicking.

Va voltage was around 60 volts, but Vs was just around 10v.

Then I did a big mistake.I disconnected the Y/sustain board to verify if VS would rise to 170v.
It has risen indeed, but reaching almost 400v !!!.

Now there is no blinking green led or relays action at all, just red led that stays on.

Following this thread from Grunder

https://www.badcaps.net/forum/showthread.php?p=724020

I ve found two shorted mosfets and a shorted diode on Ysus board.
Just replaced the ultrafast diode.

FWD 42pv1 service manual, says that micon is halted when A (micon) board, dont dont send
Relay on signal to the power supply.

But I can see that sda5550 ucontroller on A borad is working, because i see its 6mhz xtal oscillating, and it has bus activity and Grunder's experience shows that RLY signal will not go up, if theres something wrong with Ysus.

Please correct me if i am wrong.

Now the question is: Is there a way to test this knp 4840 PS with some kind of dummy loads, turning
its lil AUTO to MANUAL mode switch ?

Or should I replace those two mosfets, before trying to turn my monitor on again?

I just have 5v stdby and ACDetect on the power supply cn801 connector. No RLY or Vs/on.

Already fed the ysus board VS input with 30vdc, and Vsc and negative Vy from those lil switching transformers, seem to be working...

Thanks a lot.

[danielsoy]

Re: Sony fwd 42pv1 dont turn on.

The other switching transformer on the left side is working too, when
i feed it with 5vdc.

[danielsoy]

Re: Sony fwd 42pv1 dont turn on.

already turned the mode switch to auto position, got relays action but power correction
circuit that feed the others power supplies is doing nothing.