32" Trinitron troubleshooting

[hardwareguy]

Got a call from a man with a 32" Trinitron....its not HD, but it has progressive inputs so I figured I'd give it a whack.

Set doesn't power on. A high pitch whine is heard which lowers in intensity and pitch until silence. This immediately screams short circuit protect.

I removed the dust/tar mix (the whole family smokes...yuck!) and removed the mainboard and took it home. (we agreed that the set itself was just too much of a PITA to load in the car!)

Out comes the multimeter where I find a shorted horizontal output transistor. The base lead has a cold solder joint.

All the fusible resistors are good and well within spec. I do not have an ESR meter but the lytic caps behave as expected when measured with a multimeter. No crap caps, its all Nichicon and Rubycon. All diodes check out as well.

Now the question is should I blindly replace the HOT and make sure the joints are repaired or is there something more sinister lurking about in this set?

[Wizard]

Re: 32" Trinitron troubleshooting

Yes.

Sony is infamous for popping the horizontal transistor because of bad joints. Also check the vertical IC is good. Take the horizontal base transformer drive out and scape the pins clean and reinstall with solder and resolder the rest of horizontal circuits and vertical circuit if yiou have a vertical IC to rob from another, do so.

Cheers, Wizard

[hardwareguy]

Re: 32" Trinitron troubleshooting

I do not have another vertical IC.

By drive Xfmr I suspect that's the small xfmr near the HOT? I lack any sort of service manuals for this.

I did get a clue though....before it died the customer said the picture was shifted horizontally a couple inches.

If its the cold solder joint problem, I found only one, the base of the HOT. Sad, it could have been prevented with a rivet.

Im gonna check some more lytics....I found some 85C units sitting next to a heatsink.....shame on you Sony!