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Mitsubishi 6CT-333 "Trinescope" color projection TV restoration
I've got an interesting one for you folks. I imported this set two years ago from Japan and am finally getting around to working on it, and figured it'd make an entertaining thread.
https://i.imgur.com/a9xKwhl.jpeg https://i.imgur.com/uyvE2XJ.jpeg This is a Mitsubishi 6CT-333 "Trinescope" projection color TV, using the RCA-developed technology of the same name; it produces a direct-view color picture using three 6" R/G/B CRTs and an array of dichroic mirrors - no mask required. As far as I can tell, this was the only example of a Triniscope-based consumer TV set ever sold. I have seen pictures of one restored by John Folsom last demonstrated almost 15 years ago, and another owned by Erich Loepke which as far as I can tell hasn't been run in about the same amount of time; I believe this is the third set of its kind in the States. I am very eager to get it running to see how the picture compares to its contemporaries :D https://i.imgur.com/i38KIYA.jpeg From my research, these sets were introduced as part of an effort to lower the costs of color TVs in Japan in time for the 1964 Tokyo Olympics. The 6CT-333 was introduced in 1963 at a starting price of 92,000 Japanese yen (approx. $3k USD adjusted for inflation/converted), apparently the first of its kind to break the 100,000 yen threshold. Although still extraordinarily expensive, its contemporaries cost two to three times as much, so they really did bring costs down! A similar set with a wider "viewport," called the 6CT-338, was released in 1965. It is electrically similar, though some differences are present as its schematic available on the ETF website does not quite match my -333. It appears despite their efforts, these sets did not sell well and were unceremoniously pulled from the market after "regular" masked sets came down enough in price. They never sold in the States, despite Mitsubishi apparently having considered it at one point - a 6CT-338 was exhibited at the 1964/65 New York World's Fair. Onto my set. It is unfortunately in fairly poor cosmetic condition, but is at least complete with all knobs and trim pieces. It obviously spent a lot of time in a very humid environment, so I would imagine lots of parts replacement is in my future. The CRTs (3x 150LB22 R/G/B) test good, so I am confident the set is worth restoring in any case :) https://i.imgur.com/RQZrcj7.jpeg Lots of power supply electrolytics. Cool to see early Nippon Chemi-Con caps. I will likely end up restuffing them to keep the set as original looking as is feasible inside. https://i.imgur.com/c208GZ9.jpeg It took me a little while to figure out what this is. It is actually a very high voltage paper capacitor across the anode supply - 2300pF rated for 20kV. It was disconnected at some point, so it is presumably bad. A long time ago I purchased a big lot of very high voltage film caps and I found a pair of 0.01uF at 12kV that should work fine in series to replace it. https://i.imgur.com/tTfWkMe.jpeg The high voltage section is going to be a challenge to rebuild. Looks like I may actually need to remove the flyback and HV rectifier assembly to get at some parts underneath. https://i.imgur.com/c2Z8uH1.jpeg Here's the money shot. So many paper caps to change! Most look fairly easy to replace, since the backs of the boards are mostly accessible, but that vertically-mounted sweep section looks like a nightmare. The things I do for this hobby... Anyway, I hope to have a lot more for you all soon. I'm in talks with a vintage TV and video hobbyist in Japan who has one of these sets, as well as the correct schematic diagram he is willing to send in the mail. It will make assessing what I have a hell of a lot easier. |
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Hi to all,
Hi cj_reha, Rare set indeed, congratulations! 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. same machine photos + schematic on ETF site: https://www.earlytelevision.org/mits...trinitron.html More pictures of 2010 ETF Convention, about 10x snaps of working Mitsubishi Triniscope, starts at page 107. Document is one pdf file, 11Mb, 116 photos, Wayne Bretl's entire convention coverage: https://www.earlytelevision.org/pdf/...ntion_2010.pdf Will be following your restoration with interest, Best Regards jhalphen Paris/France |
Congratulations!
This indeed is a rare set and an interesting one to follow. 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. |
What a cool early color TV! I really hope you can get this one back to running condition, what a sweet find!
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Thank you all for the kind words!
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https://i.imgur.com/XJIoeEr.jpeg 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 :) Quote:
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! https://i.imgur.com/u66aGG4.jpeg 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. https://i.imgur.com/GuT13UF.jpeg https://i.imgur.com/R4K9Xlq.jpeg 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: https://i.imgur.com/cxLR0kR.jpeg 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! |
This will be a fun resto to watch.
This, a large screen indextron, and a roundy color are the 3 sets I'd like to some day have funds to import from Japan... Granted Japan did export and sell at least one color roundy in the US I've discovered through sorting Sam's service literature...If I could find a US export model state side I'd be just as happy with one |
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Great to see this! When you first see one of these (which I did in 1965 at the NY World's Fair), you might suspect it's transistorized, but no, it's a tube room heater.
Regarding the mirrors, I suspect the coatings will be peeling like the one that was at ETF, and if they aren't, I would really hesitate to try cleaning the coated side. Do you know if the three tubes have red, green and blue phosphors, or are they white with the color totally due to the mirror coatings? I can't remember. |
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If I find the peeling in mine I wonder if it's worth calling around to local glass shops to see if any of them do dichroic coatings? Kind of a weird ask, but I can try... The CRTs are actually R/G/B colored phosphor, they're each individually marked with their respective color. |
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Merry Christmas everyone!
The rebuild begins! I decided I'm going to start with the HV/sweep/power supply circuits. They are the most cramped parts of the set and it's probably a good idea to get the annoying stuff done first. https://i.imgur.com/ouJtTvJ.jpeg https://i.imgur.com/hnimo61.jpeg As I suspected, I had to remove the flyback and HV rectifier assembly. Look at all the parts underneath! I quickly discovered something interesting: every single connection in the set is tack soldered together. Most of the time they did not even bother to thread wires or component leads through the terminal lugs; they literally laid them down and blobbed solder on top. I guess I don't mind, it certainly makes part removal a lot easier :D https://i.imgur.com/o9O20MV.jpeg Some of the soldering conditions are...sub-optimal. https://i.imgur.com/OsnPEpJ.jpeg Phenolic assembly out. It contains three 0.5uF paper caps and two of the three 200uF nonpolar electrolytics used for coupling in the centering and height/linearity circuits. The third 'lytic is mounted by itself in a separate area; I replaced that one using a terminal strip. https://i.imgur.com/XxyjHzd.jpeg More vintage Chemi-Con caps! They felt extremely light and dried out, and tested poorly. I'm glad I replaced them. https://i.imgur.com/F7aP199.jpeg Paralleled two nonpolar 100uF's together; it's all I have on hand at the moment. Should work fine. https://i.imgur.com/hcgEkcn.jpeg https://i.imgur.com/mKJ2HGY.jpeg Restuffing the three 2000uF electrolytics in parallel with the centering controls. It keeps at least a little bit of the set original, and I don't need to engineer anything fancy for reinstallation :) https://i.imgur.com/GtXEYVU.jpeg All done! Far from perfect, but it's as neat as I could make it, and it's a little bit cleaner than it used to be. I didn't quite realize how filthy this set is until I started cleaning wires and the chassis. Whatever kind of grime is built up on everything is fairly resistant to my usual degreasers, it's requiring lots and lots of scrubbing to remove. Oh well...glad it's done. This set makes all the Predictas I've done look like a walk in the park! In the next few days, I'll be tackling the deflection circuits... https://i.imgur.com/XJUD68n.jpeg Wish me luck! :tears: |
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Hi to all,
Merry Xmas everybody! @cj_reha, nice progress! Here are 4 good photos of Folsom's Triniscope at ETF 2010. Photos by Labguy's World (Thanks!) http://www.labguysworld.com/ETF_2010.htm Found in the Wikipedia Triniscope article (references) which deals 99% with RCA's behemoth of which there is a unit at the ETF Museum: https://en.wikipedia.org/wiki/Triniscope old_tv_nut's photos of the Triniscope are here in a separate Flickr file dedicated to it. Lighter than the 116 photo pdf linked to previously: https://www.flickr.com/photos/420028...ith/4556100451 VK 2009 thread about Folsom's Triniscope (+4 photos): http://www.videokarma.org/showthread.php?t=246542 VK2005 thread: http://www.videokarma.org/showthread.php?t=39884 VK Member Erich L. has one, works, posted in the 2005 thread, still active today, VK contact info: http://www.videokarma.org/member.php?u=7983 Best Regards jhalphen Paris/France Dichroic mirror arrangement in Mitsubishi Triniscope : |
Happy Holidays Jerome!
Thanks for compiling all these references! |
Seconded - thank you Jerome!
I'm in contact with Erich Loepke/trinescope about his set. I think I mentioned this before, but he confirmed he still has it, albeit it hasn't been powered on in over a decade. I am hoping to secure pictures of it to compare to the others I've saved from across the internet. I hope everyone had a peaceful Christmas! |
I really like your workmanship on this project, clearly this is a very important project for you. In my experience the best thing I found to clean the years of grime has been good ol' Formula 409 and soft bristle tooth brushes, to clean that greasy stuff from ceramic caps I use naptha on a rag and carefully wipe them down. The only drawback to the 409 is how well it cleans tubes of everything including the numbers.
Good luck with this one, I'm very impressed with your progress. |
Time to tackle the sweep circuits.
https://i.imgur.com/xxhgefE.jpeg 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. https://i.imgur.com/jq9iCEk.jpeg https://i.imgur.com/hicRWv1.jpeg 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. https://i.imgur.com/hnqyzd8.jpeg 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! |
soldering iron looks familiar... one of those Weller's on my bench.
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Getting close to being finished with the sweep circuits:
https://i.imgur.com/ZLwFJlZ.jpeg 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 :D. Even though they all tested OK, I opted to replace most of the larger power resistors simply to free up some space. https://i.imgur.com/AYxnyq4.jpeg 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. https://i.imgur.com/BtUyvms.jpeg https://i.imgur.com/0OITfUB.jpeg 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. |
It all looks good! I am anticipating your next steps.
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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.
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