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

[cj_reha]

Thank you all for the kind words!

Originally Posted by jhalphen

See below a shot by old_tv_nut (Thanks!) when John Folsom jr showed his working set at the ETF convention.
closeup, his dichroics have tarnishes, hope yours are in OK state.

Unfortunately the mirrors in my set are quite dirty. I'm not sure if they're actually tarnished, or if it's just decades of grime accumulation.



To my knowledge, nobody has dared to open the assembly for cleaning; at least, nobody who has documented it anywhere. Even the Japanese videos I've managed to find showing working Triniscopes had visibly dirty mirrors. I'm gonna try it...I may come to regret that, but I'm willing to take the risk

Originally Posted by etype2

Congratulations!
In case you need spare parts, you might be interested in this set, or this set could be in better condition.
https://buyee.jp/item/yahoo/auction/...owsing_history

Go for it. I’d like to buy this set, running out of room, so passing.

If you think this listing is expensive, a set like it was on the market for 5K! Very rare and a museum piece at the NHK museum. Good luck with this and will be watching with interest.

You're a horrible influence! I've been watching that set for a while. I do really want a 6CT-338 to compare and restore alongside this one - and it has the optional magnifier included! - but I have to admit the price tag on that set is a bit outside my budget. Shipping fees would probably put it at just over a grand. I paid about 1/4 that price for this one; $250-300 seems to be the average for the four or five sets I've seen sell over the years. All of that being said, I do start a new job on the 2nd of January, so if it's still listed in a few months I might just end up making a bad decision.

Anyway, a few updates for tonight. I went through the set and put together a small mountain of parts for it from my stock. Surprisingly, I have everything I need, with the sole exception of a 470pF 2kV paper cap in the vertical output circuit. Hoarding pays off sometimes!



I also verified that there were no catastrophic shorts in the power supply and slowly brought it up on a series of dim bulbs. I have had good luck with old Japanese electrolytics being OK if you bring them up slowly, and this set was no exception.





Soon after taking these pictures, the 12BY7 2nd video amplifier went to air in a brilliant blue haze. It appears the seal at the pins had been weakened by corrosion most likely caused by poor storage conditions (so-called "green fuzz"), and heating the tube up caused total failure. I replaced it with an RCA spare and continued the slow powerup. Kinda sad - until then, the set had an all-original Mitsubishi tube complement!

Once it was at full B+, I installed the horizontal output tube and was greeted with a raster:



Not only were both deflection circuits working, I could actually hear an FM radio station coming through the tuner! It appears that aside from lots and lots of bad paper caps, the set is basically working. Fantastic!

After about a minute, I heard a faint hissing sound and discovered one of the paper caps in the high voltage cage was getting so hot it was actually dripping oil. I also noticed the B+ was excessive (354V @ 330V test point), riding right against the 350V ratings of the electrolytics. The set has voltage taps for 90, 100, and 110V on the back, but it appears even at the highest tap, US line voltage is simply too high to run it safely. I've decided to discontinue power-up tests until I can get the sweep and high voltage sections recapped, and I'm going to use a variac dialed down for further testing.

Finally, I have potentially secured the correct schematic for this set, which I was completely unable to find online. A new Japanese collector friend said he has sent a few copies in the mail - fingers crossed!