J
James Sweet
Guest
I finally got some renewed motivation to work on the P5073. Put the power
supply board in my working P5075 and with the help of comparing measurments
with the working board I tracked down a couple faults and got it so the set
powers up. Now the problem is it comes on and the pic comes up, sound
normal, etc but it randomly shuts off from a few seconds to a minute or so.
Pic is noticeably bright with a slight underscan at the top leading me to
believe the HV is high and tripping the Xray protection. I have a HV probe,
what should the HV read on this set? Also what could cause excessive HV? So
far I've resisted the temptation to fiddle with the HV adjustment pot and
it's still sealed.
Here's what I've done so far, set came to me completely dead.
Replaced Q104 (main PSU chopper), R119, R120, R122, and Q143 and the main
fuse, that restored some function
Replaced bulging 10uF 250v cap near the flyback (there's glue over the board
number)
And more recently replaced Q114 to fix the power relay, and D103 which
restored the 5v 60 hz square wave at the A.C. CLK pin to the video board.
I've resoldered most of the board, checked most of the semiconductors, what
else should I look at? I almost wonder if the flyback could be causing this,
but experience tells me that when large expensive parts are suspect they're
usually good.
supply board in my working P5075 and with the help of comparing measurments
with the working board I tracked down a couple faults and got it so the set
powers up. Now the problem is it comes on and the pic comes up, sound
normal, etc but it randomly shuts off from a few seconds to a minute or so.
Pic is noticeably bright with a slight underscan at the top leading me to
believe the HV is high and tripping the Xray protection. I have a HV probe,
what should the HV read on this set? Also what could cause excessive HV? So
far I've resisted the temptation to fiddle with the HV adjustment pot and
it's still sealed.
Here's what I've done so far, set came to me completely dead.
Replaced Q104 (main PSU chopper), R119, R120, R122, and Q143 and the main
fuse, that restored some function
Replaced bulging 10uF 250v cap near the flyback (there's glue over the board
number)
And more recently replaced Q114 to fix the power relay, and D103 which
restored the 5v 60 hz square wave at the A.C. CLK pin to the video board.
I've resoldered most of the board, checked most of the semiconductors, what
else should I look at? I almost wonder if the flyback could be causing this,
but experience tells me that when large expensive parts are suspect they're
usually good.