Hitachi 55HDX99 Plasma Tries to turn on then shuts off

[R_J]

Re: Hitachi 55HDX99 Plasma Tries to turn on then shuts off

That information was in a service bulletin on how to force the power supply on. There are no schematics of any of the panel boards, including the power supplies. They were never ment to be repaired and were replaced as complete boards.

[canadaboy25]

Re: Hitachi 55HDX99 Plasma Tries to turn on then shuts off

I did some probing around with the scope trying to figure out why there was no power getting to the Vs or Va rails. I probed the primary side of the transformer and was only getting a bit of noise instead of the high frequency switching that would be expected. I probed the gates of the switching transistors and only the upper one had a drive signal. So I probed the top of the resistor with a red arrow pointing to it and there was a drive signal there.

I tested the resistance of the resistors and sure enough, the resistor with the red arrow pointing to it was measuring anywhere from kohms to Mohms instead of the 120ohms it should have been. I removed the resistor from the board and tested it again. Surprisingly it tested just fine. So I soldered it back in and tested the board. I then had all of the voltages present. I put the TV back together and it's working great. The image attached is of the resistor before I removed it and resoldered it.

So a bad solder joint on a tiny smd resistor brought down the entire TV. At least it was a cheap fix.

Thanks for all the help in narrowing down the source of the problem.

[ngth82]

Re: Hitachi 55HDX99 Plasma Tries to turn on then shuts off

Nice! Thanks for the update!

[R_J]

Re: Hitachi 55HDX99 Plasma Tries to turn on then shuts off

Good to here it is fixed, these power supplies were very reliable.