Pioneer SDP5073 excessive HV

[James Sweet]

So I was within minutes of scrapping this cosmetically very nice Pioneer set
after having it sitting around dead for almost 2 years when I had some
further imspiration. Found the shorted part on the signal board causing one
shutdown and discovered the cause of the other. High voltage is excessive,
picture looks decent but washed out and shrunken, the 10uF 250v lytic near
the flyback gets hot, set will run fine with the HV turned all the way down
and Xray protection turned up but obviously there's a fault. Has anyone seen
symptoms like this? The HV adjustment works, but the voltage is obviously
significanly too high. Tried to probe it with a HV probe but arced to
somewhere and now the main PSU won't start up at all, but I'm sure I can fix
that one. I've already resoldered the entire board and checked virtually
every diode, transistor, fusible resistor, etc.

 

[James Sweet]

So I was within minutes of scrapping this cosmetically very nice Pioneer set
after having it sitting around dead for almost 2 years when I had some
further imspiration. Found the shorted part on the signal board causing one
shutdown and discovered the cause of the other. High voltage is excessive,
picture looks decent but washed out and shrunken, the 10uF 250v lytic near
the flyback gets hot, set will run fine with the HV turned all the way down
and Xray protection turned up but obviously there's a fault. Has anyone seen
symptoms like this? The HV adjustment works, but the voltage is obviously
significanly too high. Tried to probe it with a HV probe but arced to
somewhere and now the main PSU won't start up at all, but I'm sure I can fix
that one. I've already resoldered the entire board and checked virtually
every diode, transistor, fusible resistor, etc.

I should add that I'm almost starting to suspect the flyback, though it
rings good and experience tells me that when a part like that is suspected,
the real cause is usually some 5 cent part that's been overlooked a dozen
times.

 

[GPG]

Check LOPT tuning cap

 

[James Sweet]

Check LOPT tuning cap

Which is that?

I did find a leaky diode that as far as I can tell is part of the HV
regulation circuitry so hopefully that'll fix it. Now I need to figure out
the startup problem, relays click responding to the power button but the
power supply remains dead as a doornail, rectified DC is present at the
MOSFET, which is also tested good. All resistors and semiconductors in the
area appear to be fine.