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The Set: Pete Deksnis's Site about the CT-100

Restoring a Vintage Color Television Set

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info exchange

1-4-2000 Stumbled across your site on my way to Ed Reitan's pages -- great to see that your sharing your restoration experiences.

I've got a CT-100 set in my garage here in the UK, perhaps the only CT-100 outside the states -- who knows. I bought it while working in Austin Texas in 1997 (drove to Kentucky -- wife thought I was crazy). I've been collecting TV's for a little while now and have a small collection of US and UK sets inclincluding some pre-war.

The CT-100 is next on the restoration list. Its all there in 3 packing cases. The CRT was tested for emission when I bought the set and showed good, the getters look bright and it was packed for its transatlantic trip very carefully polyfoamed into a cardboard box which in tturn was padded into a wooden packing case) so I'm hopeful that it will be OK. The rest of the set was all there but I made no attempt to test anything before shipping.

Your site has wetted my appetite for making a start on it soon. I have a few extra problems to deal with here -- like getting an NTSC signal (can use a US video) and finding a 60 Hertz power supply (could use a 50 Hz 120V supply from a transformer but that normally gives bad 'hum bars' on US sets -- I display a 625 line 50 frame signal on my US B&W sets to avoid this problem).

Incidently, I know of a very good transformer re-winder here in the UK that can tackle most flybacks and field transformers at reasonable cost if its of any interest to you. I've often seen US collectors say that a dead flyback can't be re-wound -- not true. I'm almost certain that a 45 year old flyback operating at 20 kV would have a very short life expectancy!

1-5-00 [but posted 4-22-00] I was intrigued by your comments on the fate of your picture tube for the CT100. Very strange that you would get a current flow but no glow from the heaters. Has the tube gone soft? Are the getters white? [
Yes and yes. I'm afraid the "heat" came more from profuse optimism and a sweaty palm than Ohm's law. --Pete : ) ]

I started thinking about how one may recover a 15GP22 with an open circuit heater. Back in the early seventies I bought my first colour set from an ex-rental company. It came 'untested' but at around the equivalent of US$100 it was a big investment for a 13-year-old!

Horror of horrors, the picture tube heaters were open circuit! I was despondent! Desperate! A rebuilt tube would cost me another year's pocket money! In search of a solution, I talked to an old hand at a local TV repair shop. He described a process that I've never heard mention of elsewhere (though maybe common knowledge amongst professionals). He described how you could sometimes 'weld' the heater wire back together with a short burst of high voltage on the heater pins. Desperate to try anything, this is what I did.

I connected a length of the cable to one of the heater pins, connecting the other heater pin to ground. Then using a monochrome set as a power supply (chassis' connected) I momentarily brought the end of the cable close to the anode of the horizontal output tube, drawing a sizable arc. I then checked continuity and had to repeat this process three times before, amazingly, the heaters now showed continuous. And even more amazingly the tube lit and performed really quite well.

I used the set for a number of years, and although the tube slowly lost emission, it was still watchable when finally I scrapped the set! I've never tried it since and needless to say, this was a pretty dangerous procedure for a 13-year-old to be undertaking, but thought I'd share it with you just in case you might like to try it on an otherwise useless CRT!

3-27-00 Glad to hear that you're making progress toward a rebuilding method for the 15GP22; though I'm hopeful that my set has a working CRT it's still good to know that a rebuild will become possible.

I've finally made a start on my CT-100. Job one is total replacement of the paper caps. I have some sympathy with your 'if its not broken don't fix it' and in the past I've tried to 'fault find' my way to a restoration. However, I've slowly come to the conclusion that to get a lasting restoration and decent performance, the paper caps have got to go.

I think what finally persuaded me was the restoration of a Decca 1000 projection set (a Brit. set of around 1950, 26 tube, 4' x 3' screen). By the time I had the set working well, I'd replaced 80% of the paper caps anyway, and spent hours and hours fault finding. No sooner had I declared the set restored, than it faulted again. I had to revisit it three times, the final time I replaced every last paper cap. It's remained reliable since.

I do, however, take your approach when it comes to electrolytics. From my experience, they are very much more reliable than paper caps. If they are not leaking, I'll keep them in and always try to reform the can types.

While re-capping, I also check out high resistances, say anything over 500k, and generally 'tidy up' previous repairs. Its also a good way to get familiar with the chassis layout.

One tip I picked up from your site was about the reliability of those white peaking coils. Mine now resemble hailstones, the surface rough and cracked. And the leads have all a layer of green corrosion. And, every last one of them measures open circuit!

So, plenty to do!

4-6-00 Made pretty good progress with the re-capping. There is just one cap I'm having trouble sourcing, that 6000V focus smoothing cap. Any ideas for a source?

I've also replaced all the white peaking coils, and replaced about 20 resistors that checked out high or open.

The power supply electrolytics all reformed well, though I still expect I'll need additional smoothing to cope with the 50-Hz supply.

During the re-cap, I tidied a lot of previous repaired. Many original R and C's had had one leg cut free and then resoldered. Though I know this is quite a common fault tracing technique, the shear number of components this had been done to surprises me. Yet the inside of the HV cage is very clean. The flyback is original, with hardly any of the thick gunge that normally collects around the HV rectifier. Strange. On the one hand this set looks like its had 1001 service visits, yet under power for next to no time. Could it have been used for training? A demo set of some sort? Or just always operated in a very clean environment? All ideas welcome!

I've hooked up the chassis to a Sylvania 'Color Check' monitor. This is essentially a 14" colour portable cabinet fitted with just the CRT, scan coils and a focus network. I've set the Color Check up for 12 mH yoke inductance. This set up will allow me to get the chassis up and running on the bench. I intend to leave the 15GP22 in its packing case 'till I'm sure the chassis is OK.

The chassis currently powers up well, and is 'working' to an extent, producing a 10" x 8" raster on the Color Check (guess the 45 deg 15GP22 needs very little deflection drive). HV is low at around 15Kv, suspect the HV rectifier is soft. Tuner, IF, sound and luminance all check through OK, and I can get a decent monochrome picture. Haven't got the chroma sections checked out yet, for one thing the crystal is missing. I'll fix a HC49 crystal below decks for now. As a signal source, I've set up a VGA-to-TV (NTSC) convertor. Now I can 'paint' my own test patterns!

5-1-00 Here's a brief update, and a request for help finding a replacement brightness control!

I finally got around to testing all the tubes in the set, and found 12 at or below rec emission, including all but one 6AN8 and the 6CD6 (probably explains the low eht!). All the tubes are available in the UK, but for some reason (probably because there are no European equivs.), the 6AN8's are very expensive ($15). So I've ordered all the tubes from AES and await their arrival.

This has given me some time to dust off and re-cap an RCA WR-59C sweep generator I'd bought for $5 when I was in Texas. It now appears to work well, so aligning the CT-100 becomes possible, that is if I can follow what must be the most complicated IF alignment procedure ever conceived by RCA.

To cope with the 50-Hz supply, I've also doubled up on the electroytics in the voltage doubler and 400V smoothing circuits, by fixing two 220 uF and a 100 uF electrolytic below chassis. I've also fitted a RTC inrush limiter (where the two mains filter caps used to be, now earthing their replacements to the chassis at the picture tube heater earth point). This has all but eliminated any 50/60-Hz hum interference, and the transformer sounds less stressed at switch on.

I've also had chance to check out the defective brightness control. It was found open circuit and I temporaily wired another pot externally. I had hoped to dismantle the original and possibly repair it, but the wirewound track is now just a tangle of fine wire. Anybody have any ideas where to find such an unusual spec. pot? If I could get hold of a similar shaped 5k wirewound body I think I could swap the tracks over (the volume/mains switch are both OK). So far my searches through UK sources (and Harry Potter) have drawn a blank. BTW, the inductors I used to replace the white peaking coils are modern production Siemens ferrite core, using two in series to exactly match the specified inductances). Whether they will perform identically to the originals I can't say yet, I'll let you now when the new valves are in and I sweep the IF/Chroma/Video strips.

Just a thought for your web site. Would it be possible for you to put dates against the info exchange names so that updates would be obvious? It looks like you're making good progress toward the 15GP22 rebuild. As I get my chassis near completed, my apprehension about unpacking the picture tube increases. What if I find the getters white or a crack in the face plate? The stuff nightmares are made of!

9-2-00 All progress on the CT-100 stopped for summer, but with Autumn approaching I guess I'll be starting again soon. Still have a problem trying to source that brightness/volume pot though.

I saw on the site that an Westinghouse is going to be auctioned. I know it would cost a fortune to ship it over her, but I can't help being interested. When is it due for auction? [
It was removed from market by the owner September 14 before it ever hit ebay. --Pete ]

Trust, like me, you're thinking of dusting off THE SET ready for winter!

9-30-00 Steve very kindly sent me one over (the brightness pot actually) and I've just received it. Very good of him to take the trouble. I hope to repay the favour somehow. He's restoring a pre-war RGD set so I might be able to locate something for him.

Hope to get some time in on the CT-100 soon, though demands of work mean I'm travelling a lot between now and early November. Thanks again for your help.