Panasonic CT-1310M keeps blowing horizontal output transistor

[luRaichu]

I just called up a bunch of shops and techs in Maryland and nobody in the area can or will work on my Panasonic set. I guess I'm still on my own here!
So, how should I test, order, and replace bad diodes/transistors in the PSU/Horizontal circuits? Those are the only problem I can think of.

[ARC Tech-109]

[QUOTE=luRaichu;3257145]I just called up a bunch of shops and techs in Maryland and nobody in the area can or will work on my Panasonic set.

This doesn't surprise me really, the number of "TV-Radio" repair shops remaining are but a small fraction of what they were a quarter century ago. Most of those techs are retired or have become silent and the few that are around know little to nothing of the legacy technology. I grew up in TV shops having them in the extended family, both had closed up by the mid-90's because the business dried up.

So what to do about your ailing Panasonic Color Pilot:
If it was me I'd go back over my work again after a short break, say a week or more to get it out of my head.
Starting over with in-circuit checks of transistors knowing the junction is about 0.75 volts, I use a Fluke model 77 DVM that I've had since the mid-80's and it has a real diode check function that shows the actual junction conduction voltage. Okay so the semiconductors all show the correct forward drop in their respective directions 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. When I say bad I mean internal current leakages and high ESR values. More often than not I will use salvaged capacitors out of the last generation surround receivers that had worked but replaced for an "upgrade" and these salvaged units are performing well. One of my present 16:9 monitors is a Panasonic CT34WX54 widescreen CRT that is presently running salvaged electrolytics along with ALL of my Sony PVM-5300 triple monitors I use for production work. 1984 vintage take-outs from the local FOX affiliate with millions of hours they got recapped with salvaged caps and work as they should. 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?
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. 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? 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.

The problem here unfortunately is a lot of variables have been added and it's become a circle of tail chasing with the only solid result being shorted horizontal output transistors and frustration. Replacing capacitors was a necessity, you pulled one that was missing a lead that had corroded away however without the necessary test equipment you're still trouble shooting from the hip.
Those flybacks have been known to short & fail, the ones I've experienced won't even run long enough to light up the screen but that's not to say it couldn't while eating expensive transistors along the way.

I've been going through all of your posts trying to put together a summary of what has been accomplished to this point. Electrolytics replaced, resistors tested and a complete resolder. This is the one that I'd focus on first, with a magnifying glass and lots of time. All it takes is a bridged pair of pins on an IC or between two close spaced leads to throw everything into a tailspin. Have you carefully done a visual on the board and I mean out of the chassis? 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. From there I would be looking at every connection following the traces around and giving attention to the closely spaced leads for any sign of a bridge. This can take some time... a lot of time. I'm also seeing a lot of frustration and impatience, I pick up on these things. It's this frustration and impatience that makes a big pile of smoked parts.
What I can't do is fix this over the internet despite my past experience with them, until I actually get my hands in something and a feel for what's going on all the explaining in the world is not going to help, this is why I say to go back on all of your work starting with fresh eyes after taking some time away from it.

Options and I'm being serious here. One is you could keep at it and take things step-by-step. Two is finding a someone willing to work on the set but that sorta defeats the prupose doesn't it? I mean you fixed a McIntosh right? Three is you could box it up and donate it to me so I can fix it and add it to my collection saving the remaining horizontal output transistors of the world from certain destruction. I'd even pay the shipping.

[JohnCT]

Originally Posted by ARC Tech-109

I grew up in TV shops having them in the extended family, both had closed up by the mid-90's because the business dried up.

Did they miss the renaissance or what?

In the mid 90s, I made a fortune servicing RPTVs and even tons of CRT TVs like the RCA CTC17X series as I was an ASC for Thomson. I was doing between 5-10 CTC 175/6/7s a day. I knew them so well I didn't even look at them before calling the customer to give them an estimate (I pretty much flat rated them based on screen size). Most were corrupt eeproms from bad grounds on the tuner shield, horiz output, and regulator output heatsinks. A few flys here and there but the flybacks were pretty cheap.

On rear projection TVs, most problems with Japanese brands were convergence related and I used to buy STK modules a hundred at a shot.

The RCA rear projectors didn't have convergence problems (all discrete components) but the guts were built in a crate - two brackets and two unplug harness and the box was out of the TV and in the truck in 5 minutes. Most RCA projection problems were smps rebuilds or HV splitter boxes.

Good days.

John