Philips plasma keeps blowing VS FETs (Samsung ps-424-ph PSU)

[Dannyx]

Good day folks. I've recently fixed a 42 inch Philips plasma display (or so I thought) which had 2 shorted FETs that drive the Vs. Trouble is the repair only lasted a few days: now the same FETs are dead-shorted again (along with the fuse, of course). The power board is a Samsung ps-424-ph (I can provide photos if need be), but what could be overloading the Vs bus to cause such behaviour in the first place ? The X/Y boards have their fuses intact. Does this happen when PDPs get old and begin drawing more power ? The FETs are FQA24n60.

[ReeceyBurger123]

Re: Philips plasma keeps blowing VS FETs (Samsung ps-424-ph PSU)

Did you replace the driver for the transistors and related capacitors for it ? have serviced a few of them supplies one with shorted pfc fets. I replaced all surrounding capacitors (smaller ones) and the driver for it the caps go high esr causing a noisy input to the controller and it will see a lower in put in general which can throw the controller off and cause it to throw a wobbly killing the fets.

My advise replace the controller and smaller capacitors in that area.

[Dannyx]

Re: Philips plasma keeps blowing VS FETs (Samsung ps-424-ph PSU)

Did you replace the driver for the transistors and related capacitors for it ? have serviced a few of them supplies one with shorted pfc fets. I replaced all surrounding capacitors (smaller ones) and the driver for it the caps go high esr causing a noisy input to the controller and it will see a lower in put in general which can throw the controller off and cause it to throw a wobbly killing the fets.

My advise replace the controller and smaller capacitors in that area.

Thanks for the info, though those are not the PFC FETs - they're the Vs FETs...anyway, same concept, I got the gist. The controller is on a small riser board, but I don't think it's worth the headache at this point - already wasted too much money on this thing, so I'll just give it back to the guy and that's that - end of story.... The caps on the other hand could be bad, since I haven't replaced any. Makes sense, since they're at the top of the cabinet where all the hear rises...tough with no ESR meter :|

[Dannyx]

Re: Philips plasma keeps blowing VS FETs (Samsung ps-424-ph PSU)

Here's the PSU in question - rings any bells ? The FETs are on the heatsink right next to the green transformer at the middle-top. The controller is the riser to the right of that. I'm guessing the cap I should've replaced is that small one next to the riser. There's also a solid polymer one on the riser itself...