Sony KPR-46EX32 RPTV intermittent picture

[randy]

I have a 13 year old Sony KPR-46EX32 RPTV. Last weekend the picture
started suddenly going completely black after between 20-90min of
operation. I have a service manual and pulled the "A" and "G" boards
out on the floor behind the TV. The DC voltages all seem to be ok.

A couple times, probing the -135V on the "G" board connector with my DMM
has restored the picture. Searching the web, I found a service website
for PC monitors that mentions Sony monitors are notorious for having
flaky protection circuits that will erroneously disable the HV
circuits. Wondered if this could be a similar problem and by probing it
I was changing the voltage just enough to reset it. If anyone knows
where I should look to repair this, I'd appreciate it.

TIA,
Randy

 

[Art]

May want to remove the boards and check for poor solder connections on the
boards, while there use an esr meter to check the caps in the powersupply
and deflection circuits. Good mag glass and light source will assist in
seeing the cracked solder connections.

 

[Leonard Caillouet]

Actually this model would be more notorious for bad solder joints causing
this problem. Look for the obvious first. If you get into troubleshooting
the protection circuits without some experience you will likely chase your
tail.

Leonard

 

[Jerry Greenberg]

Check for cold solder connections, and for caps having high ESR's from age.


Jerry G.
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