Mitsubishi 6CT-333 "Trinescope" color projection TV restoration

[cj_reha]

Time to tackle the sweep circuits.



It's a challenge alright! The caps on the PCB weren't so bad, but the point-to-point sections are extraordinarily messy. I keep spotting more caps tucked away behind bigger components.





I ended up needing to remove the power supply choke entirely because a 0.1uF paper cap was tucked behind it and part of the harness. Oh well, it opened up the area a little bit.



Dicey!

Outside of the caps, every single carbon comp resistor I've tested is 30-50% out of spec. It tracks, what with the set obviously having been stored in a high moisture environment for a while. I've defaulted to changing them without testing at this point. Interestingly, the dogbone-type resistors are mostly all OK, within 10% or better; I haven't needed to replace any of those. I suspect they are an early type of deposited carbon film that ages better.

More soon!

[ARC Tech-109]

soldering iron looks familiar... one of those Weller's on my bench.

[cj_reha]

Originally Posted by ARC Tech-109

soldering iron looks familiar... one of those Weller's on my bench.

They make good stuff! It's a WES51 I got for my 16th birthday - 22 now, and it still gets used on a daily basis. Only on the second set of tips because I lost most of the originals in a move. It's paid for itself many times over.

[cj_reha]

Getting close to being finished with the sweep circuits:



I have nothing to say other than "phew!" Somehow I managed to avoid singing any stray wires with the iron which I am fairly proud of . Even though they all tested OK, I opted to replace most of the larger power resistors simply to free up some space.



Power supply choke reinstalled and all wiring roughly re-dressed how it was before.

The next step before I power it up is to restuff the power supply electrolytics.





Nobody will ever know...

Honestly, as I go through these caps, I somewhat regret cutting them apart; they aren't dried out at all and the paper/foil are in great shape. But the rubber seals look pretty bad and I worry about them failing in short order after so many years of unuse. In any case, they'll be more serviceable in the future.

[ChrisW6ATV]

It all looks good! I am anticipating your next steps.

[Electronic M]

Great work so far. I do see one thing I find concerning....That last pic of the lytic you're restuffing the leads between the old and new terminals are bare and look long enough that when assembled they could potentially short to each other or the can. If I were you I would desolder one end of each, slip some heat shrink over and resolder. It would suck if they shorted and took out something hard to replace.

[cj_reha]

Originally Posted by Electronic M

Great work so far. I do see one thing I find concerning....That last pic of the lytic you're restuffing the leads between the old and new terminals are bare and look long enough that when assembled they could potentially short to each other or the can. If I were you I would desolder one end of each, slip some heat shrink over and resolder. It would suck if they shorted and took out something hard to replace.

Don't worry - the wires weren't soldered in place yet, I just ran them through the drilled holes for a photo. I only wrapped & soldered them once the lid was on top so there's no excess length and no chance for them to short on anything