Help fixing a Sony 2010QM pinamp issue

[soviet9922]

Hi, like a couple of years ago found a wonderful Sony 2010QM monitor initially it was not working has a bad fly-back and horizontal transistor on it but after replacing the parts started working great.
Have it running quite often excellent brightness and picture, but then took some vacations and was unplugged for like 2 months.

When i got back after connecting it and turning it on a clear issue was show up some kind of pin-amp issue:


So thinking this is going to be an easy fix try adjusting pin-amp on the board but no effect can't correct it.
Probably old caps on the deflection board, started removing the electrolytic's and checking them one by one all of them where OK according to the cap meter and ESR tester.
Replaced 95% of the caps on the D board anyway "just in case TM" but no effect exactly the same issue continue.

Then checked the PSU inputs on the Deflection board, 12v 15v 8v and 115v all OK and almost spot on.

Checking on the schematics the only thing i found was that pin 16 of IC 801 (TDA-1082) has 12v in place of 15v.



Kinda lost on what i can check next open to any suggestions and help.


Pictures from the board:










Attached is the schematics on google drive:
https://drive.google.com/file/d/1UP3UMp ... sp=sharing

[matt]

The most common failure point in the pincushion circuit is the pot itself. Try testing that first.

[soviet9922]

The most common failure point in the pincushion circuit is the pot itself. Try testing that first.

The pots are 3 small trimpots on the pcb itself, cleaned them and checked the pots they are fine.

[MKL]

It can't be seen very well in the pics but I think the supply voltage to IC801 (pin 1) goes through a resistor (R803 in the schematics in the supplement). Check that it's not open and you have 12V on that pin. But probably the output transistor Q801 is bad. Desolder it and test it. It's an NPN so you'll have readings of about 0.500-0.600V across the B-C and B-E junctions and OL when you invert the meter leads. The pincushion distortion is narrow and not wide which excludes a dead short across C and E. It could be leaky. For the same reason shorted C804, C541, D510 are also excluded. So it must be a problem with Q801, IC801 or IC504. Sure, a bad passive in series with the correction signal (C568, R598, R813, RV803) would have the same result but it's less likely. An oscilloscope would allow you to see if the sawtooth wave from the vertical deflection makes it to IC801 (pin 10) and if IC801 converts it to a parabola on pin 15 and collector of Q801.

C568 is shown twice in the schematics. It must be a mistake.

[soviet9922]

It can't be seen very well in the pics but I think the supply voltage to IC801 (pin 1) goes through a resistor (R803 in the schematics in the supplement). Check that it's not open and you have 12V on that pin. But probably the output transistor Q801 is bad. Desolder it and test it. It's an NPN so you'll have readings of about 0.500-0.600V across the B-C and B-E junctions and OL when you invert the meter leads. The pincushion distortion is narrow and not wide which excludes a dead short across C and E. It could be leaky. For the same reason shorted C804, C541, D510 are also excluded. So it must be a problem with Q801, IC801 or IC504. Sure, a bad passive in series with the correction signal (C568, R598, R813, RV803) would have the same result but it's less likely. An oscilloscope would allow you to see if the sawtooth wave from the vertical deflection makes it to IC801 (pin 10) and if IC801 converts it to a parabola on pin 15 and collector of Q801.

C568 is shown twice in the schematics. It must be a mistake.

Thanks for the information checked all this components and where ok, has failed previously to check thoughtfully the pinamp and pinphase pots they where defective ended up removing and checking outside the circuit.

[soviet9922]

The most common failure point in the pincushion circuit is the pot itself. Try testing that first.

Thanks you where right failed to give a good check before but now removed them and out of circuit the pots where wasted.

[soviet9922]

The red pots where bad.
Its very surprising considering they are inside the monitor and probably where never touched or adjusted before.

[matt]

Thanks you where right failed to give a good check before but now removed them and out of circuit the pots where wasted.

Awesome! For some reason, the pin amp pots fail very consistently in this generation of Trinitrons. Of course there are plenty of other ways to lose pin correction but this seems to be the most common (also the easiest to deal with).