Panasonic CT-1310M keeps blowing horizontal output transistor

[luRaichu]

Originally Posted by ARC Tech-109

I then move on to capacitors. You said that you have replaced a majority of electrolytics, what did you use? This is very important as the vast majority of chinesiums are bad right out of the box.

I used mostly Würth Elektronik & a few Nichicon caps. I would never trust the cheaper brands like "Elite".

Originally Posted by ARC Tech-109

Have you gone over the top of the board and actually verified each capacitor is the proper value according to the schematic AND the polarity is correct?

I couldn't cross-reference with the Sams' as I don't have all pages; but I've checked and every new cap installed is the exact same capacitance, same voltage rating or higher as it's predeccessor. Polarity is easy because most if not all caps on the main board have their negative side facing right.

Originally Posted by ARC Tech-109

Okay so we "think" the electrolytics are good being name brand parts like Nichicon then I'd move into the various supply voltages following the schematic. With the horizontal transistor blown I'd remove it from the circuit and sub in a 40-watt incandescent lightbulb between the emitter & collector to load the main part of the power supply, no you won't have any sweep but this is not important at the moment... an oscilloscope however would be most helpful and the reason for this is even without the HOT in place there should still be drive available on the collector of Q501 unless the failsafe has an issue. Without horizontal pulses coming into the failsafe it shouldn't trigger a shutdown. How about voltages? We don't need exact numbers here, +/-5% is a good working margin.

As you might have seen, I measured and re-measured the PSU voltages prior to the +B regulator taking a nose dive. Everything seemed up to spec then.
Also, I agree, an oscilloscope would be useful at this point. Perhaps I'll look into getting one. But I think the 100 watt lightbulb in the post-recap +B circuit overloaded the PSU or something else, and caused damage. That's why I somewhat suspect burnt resistors, diodes, and transistors as they may have had their power rating exceeded by the bulb's current draw.

I tried running with a much smaller 15 watt bulb in place of the +B fuse but the set wouldn't power up this way. Only a feeble whine. After I removed the bulb, that's when +B started floating around low.

Originally Posted by ARC Tech-109

That being said what are the voltages going on the various circuitrace flags listed on the schematic? If they're within the spec tolerance how about at the various collectors of transistors or the VCC point of IC301?

Good call. I will check this.

Originally Posted by ARC Tech-109

I've been trying to follow along the schematic you posted the image of but the hosting site is a pain and I can't see the whole thing.

You can download them from the hosting site and magnify with your image viewer of choice. If not I can put the schematics up on the Internet Archive and you may see them better there.

Originally Posted by ARC Tech-109

Don't like the smell of flux? Sorry but it's a fact of electronics repair and you will have to deal with it. Personally I'd pull the board completely and do a de-flux using the fuel additive "Purex99" in the red bottle, that is 99% pure isopropyl alcohol and that will take ALL the flux off with a little scrubbing with an old toothbrush.

It's only the OLD flux that really smells like shit. I've always been fine with it though, but my neighbors sure aren't.
Couldn't you use the 90% alcohol they sell at drug stores?

Originally Posted by ARC Tech-109

I mean you fixed a McIntosh right?

Yes, but all that'd brought it back from the dead was a complete and utter recap. Despite this I couldn't save the floppy drive & ye olde spinny hard drive soon died from goopy head bumpers.
Also this was one of the cheapo, "pizza box" form factor Macs. They weren't the early compact ones with a 9" CRT built-in, you had to source your own monitor for these.