I have been working on my CT-100 on and off for about 4 months now. Life keeps getting in the way of this important process. :). Anyway, I was reading on Pete's site that it is recommended to replace the HV filament windings on the flyback and I am wondering what the experiences of the group were on this topic. Is this a common failure point? If so, does anyone have a recommendation as to where to get about 3 ft of flexible HV wire? The 2nd anode stuff I have is too thick and stiff for this application.

Secondly, when replacing the Selenium stacks with diodes, has anyone found the need to add additional resistance to compensate for the voltage drop that was present with the seleniums? I have not applied power yet so have not made any measurements myself. Wondering what others have found.

I'm hoping to have the old girl running by Christmas.

Thanks in advance.

Hi Tim:

I have restored four CT-100s and have not replaced the filament windings on any of them. Perhaps I have been lucky that the originals were good and continue to work. As far as the rectifiers, I just sub in the new ones without any resistors. Of course I keep the originals in place but just disconnect them from the circuit.

Steve

I have also restored 4 CT-100s and a couple of 21CT55s, and have never replaced the filament windings. I've also kept the original seleniums in every one of the sets. I think these sets were operated for so few hours that the seleniums are still good.

I did add additional fusing - especially in the cathode of the horizontal output tube. However, I have never had a flyback failure, so I think they are pretty tough.

Thanks guys. I think I will leave the fly alone.

I have added the extra fusing. I attached a fuse holder for the cathode under the chassis near the HO tube. My approach to the additional B+ fusing though was to make use of a 3/8" thick phenolic block I have had laying around and use the disconnected seleniums as a mounting shelf. I drilled and tapped the block and mounted the fuse blocks and diodes on it. This keeps the set looking original and the B+ protected by the cage while allowing acces by just removing a few screws.

I used two 3A 1000V diodes in series to replace each stack. Overkill but it should be trouble free.

I have attached a photo.

Tim,

I have replaced the selenium rectifiers with diodes, no dropping resistors needed. I restored a CBS RX90 which subsequently developed an arc over from the filament winding of the HV rectifier to the flyback core, so now when I restore a set I replace the filament wires out of paranoia. I use that very flexible silicone wire rated at 20KV or better. I can send you some if you need it.

I would recommend adding fusing downstream of the purity control and the field neutralizing control. I have had more than one set develop a B+ fault which burned up one or both of these hard to find pots. I just seem to be unlucky.

Good luck!

Thanks John. Much appreciated. Paranoia is a good enough reason for me. I'll e-mail you my address in case you don't still have it.

I have already fused the pots.

How's the CRT on yr CT-100 ? That seems to be the deal-breaker on way too many of 'em...

Luckily, the CRT is good which is why I went ahead with the electronic rebuild of the chassis. I have attached a photo of my CRT being driven by another member's restored chassis. Nothing was set up or adjusted so convergence is off, but it works!

Hi Tim:

Nice job with the fuse/rectifier block, it looks very professional.

One thing to watch out for on a CT-100, the convergence transformer. If it goes out it can take the focus pot along with it. It is not easy to find an original replacement for that pot. If your transformer is bad John sells replacements.

You probably already know this but the high voltage regulation on a CT-100 is nothing to write home about!

Steve

Along with what Steve says about the convergence transformer, be sure to change the HV capacitor from the focus pot wiper to ground. If it becomes leaky, it will destroy the focus pot, and they aren't easy to find.

I was not going to bring up the convergence transformer, but it has been my exprience that they are prone to failure, either going open, or worse yet, shorting secondary to primary or frame, which may burn up the focus pot.

I have seen most or the horror story failure modes in early 15" color sets, which is why I a bit paranoid and take extra precautions to try to prevent trouble before it happens.

Thanks for the comments guys. Yes, I have installed a "Folsom Special" transformer. John, you may recall I picked one up when I visited you.

I melted the potting tar and old transformer out of the housing and put the new one in. I left the tar out though. The old transformer secondary measured about twice what it was supposed to.

Steve, I was wondering about those HV "doorknob" caps but as they are typically good, I was going to leave them alone until I brought it up and see if there are any issues. Steve, or anyone, is there a source for the one connected to the focus pot?

Allied sells a good variety of high voltage tubular capacitors at reasonable prices.

Thanks Steve,

I have already changed that cap and have purchased from Allied in the past. For some reason, I thought you were writing about one of the doorknob caps.

The doorknobs seem to hold up well, and if they fail they don't damage other parts in the CT-100.

I agree with Steve. I have never seen any of the lower voltage doorknobs assockated with the focus or convergence circuits go bad, though I have had several of the 30KV doorknobs in 15" color sets fail. They did not hurt anything else when they failed, as the HV rectifier tube provides som isolation. But like the filament windings and convergence transformer, I now replace the 30KV doorknob with a "modern" one. There seem to be plenty of 30-40KV doorknobs available on ebay these days.

Hope everyone had a great Halloween. After the trick or treaters quit ringing the bell, I grabbed a Peanut Butter Cup and decided it was time to put some volts to the chassis.

Tonight was a meaningful night to do that as it was 50 years ago tonight that I, as a young trick or treater, saw color TV for the first time. I'll never forget when that lady opened her door and there in the living room was a huge wooden TV cabinet displaying a COLOR picture! (CT-100??) I don't think I even knew color TV was possible before that night. It was 10 years later when we finally got a color set.

Anyway, I removed the Horiz Output tube, plugged all of the coils and speaker, connected a few voltmeters and ammeters and started cranking the variac. I think it has been at least 15 years since this chassis had power applied. At about 90 volts I heard noise from the speaker and kept going to 115V. Voltages and currents did not seem out of line. I rotated the tuner one click and there was audio from the newscast! A little rotation of the fine tuning control brought it in perfectly. It is always a great feeling to have a set come back to life but this one feels better somehow.

I shut it down after about 15 minutes. after I took some readings. I noticed that the Field Neut. pot was a little warm to the touch. Not sure if this is normal so I would like some confirmation on that.

Here are my voltage and current readings and would be curious to know how these compare to other's readings. Again, no Horiz output or CRT so these will change.

Line: 115V 3.3A
380: 402V
375: 393V 50ma
285: 291V 275ma
275: 275V 140ma
175: 188V
-30: -23.7

I think I'll grab another Peanut Butter Cup. It was a good Halloween.

Tim,
Those voltages seem quite reasonable. The field nertralizing pot carries B+ current, so it will idssapate s bit of power. I think it is time to put the HO tube back in its socket and generate some photons!

John

I've missed all the foregoing good stuff sunning myself in South Carolina for the past four days. Great to hear another CT-100 will soon join the operational list. Good luck. Tim, with the attempt. Just keep an eye on the focus voltage either by monitoring the 19.5 kV HV (it takes a 10 kV or so dive when it's in trouble) and/or the 1X2B focus rectifier for stress.

Welcome back Pete. We were in down SC for a week in the summer. Great place.

HO tube back in, power on and we have photons and a steady 20KV of electrons as well! I let it run for about 15 minutes - no snap, crackle or pop. While it was running I fugured I'd put the scope probes on the red, green and blue video outputs and see what there was. I got a recognizable video signal on all three. Seems like I am off to a good start, sound and video.

Pete: What should I be looking for regarding the focus voltage? What is the failure mode or point?

Tim,

You should have 3.5-4.5KV on the cRT focus electrode. The only likely sources of failure would be the filter cap on the wiper of the focus pot, or the convergence transformer, both of which you have replaced. So I would not expect you to have focus issues. Have you put the chassis in the cabinet and fired up the CRT? What resultas are you getting?

Later on when you monitor the video outputs with a color bar signal input, here's the challenge: check for twice the red drive as the green. As shown in the link of a CTC2 driving a good tube, the red drive (bottom) is about 60 volts vs about 30 on the green video.

http://home.att.net/~pldexnis/CTC2_how_it_works/bars-15GP22-60R-30G.jpg

Hi folks:

I have 4KV focus voltage. Red drive is twice the green drive. I do, however, have alignment/IF issues that need to be sorted out as, although I can tune in a signal, the video is very noisy. Audio sounds clean.

I have not put it in the cabinet as of yet as the CRT is boxed up and the empty cabinet is in storage. It needs some refinish work. I wanted to get the electronics working before spending any time on the cabinet. I will probably get it out this weekend.

Stay tuned.

Hi folks:

I have 4KV focus voltage. Red drive is twice the green drive. I do, however, have alignment/IF issues that need to be sorted out as, although I can tune in a signal, the video is very noisy. Audio sounds clean.

I have not put it in the cabinet as of yet as the CRT is boxed up and the empty cabinet is in storage. It needs some refinish work. I wanted to get the electronics working before spending any time on the cabinet. I will probably get it out this weekend.

Stay tuned.

Tim,

I also had good sound with a very noisy picture on my CT-100. Not exactly a technical fix, but I cleaned the brass contacts on the tuner drum, which were quite dirty with corrosion. Improved the picture dramatically. Give it a shot.

-Steve D.

---

Noisy video sounds like a peaking coil issue perhaps.

Tim,
If you have a 1V or more composite video source, you can feed video directly to the grid of the 1st vidoe amp (remove 56h IF amp). If you still have noisy video, it is simple to signal trace through to the CRT grids to isolate the porblem. Is the noise only in the Y channel, or is it only in the color portion of the signal? And if the noise clears up when you inject a signal, then as suggested by Steve D., I would try cleaning the tuner before any alignment is attempted. You might also check to ensure the AGC is operating properly.

Evening folks:

Yeah, Alignment is the last thing to touch, I learned that the hard way many years ago but thanks for the warning. The tuner is definitely at least part of the problem so you nailed that one Steve. I injected an IF signal and was able to adjust it so the display on the scope was fairly clean and stable. I then threw a tuner sub in and the signal was greatly improved over the original tuner. Tomorrow I'll open it up and give it a good cleaning. I will then proceed from there. I intend to get the video looking good on the scope before trying to reassemble the CRT and cabinet.

Interesting you mention the peaking coils Chad. Some were, of course, open from the well documented corrosion. I replaced them using the part numbers recommended on Pete's site. I assume these are known to work OK.

I really appreciate all the suggestions and support guys.

I have several of those peaking coils N.O.S,that the actual manufaturer sent me as "samples" they had still in stock and sent them to me no charge..they are improved over the wax coated ones originally used in the ct-100, "J.W.MILLER" was the manufacturer i have 2 of the 220 uh,1 of the 1500uh,2 of the 6200uh,and 1 or 2 of the 1000uh,and 5 of the other 2 values used in the ct-100(i cant see the uh,i will have to look up part numbers..)
but you can have all these ,these were left over from my CT-100 restoration,i dont ever see getting another CT-100 in this lifetime..LOL
if you want them then give me your shipping info..
terry

Thanks Terry, your offer is greatly appreciated. Sure, please send them and let me know what you want to cover postage, etc. I will use what I need and pass whatever is left on to the next guy. I'll PM you my address.

CT-100 alignment is tricky. Beware that the Sams and the RCA manual have one of the waveforms inverted. I can't remember which one, but it was posted on Pete Deksnis's site a while back.

Thanks very much Steve, I did read about that and other errors as well. It sure is great to have access to the experiences of others.

Not much time to work on it today but when cleaning the tuner I found that the K3E mixer diode is essentially a 10 meg resistor. Anyone have a suggestion for a good sub? Hopefully something common.

1N82A should work fine.

I left the alignment alone on my Ct-100,it worked well,i had it hooked up to a HDTV downconverter,set to channel 4,however i did have to tweek the 3.58,but that was fast and easy,the i.f and other chroma alignment seemed too confusing in the manual,and was not real clear..one other thing i did to my CRT was seal the glass to metal seal with a layer of "VACSEAL" and i actually put it on the brass crimp nipple area on the base,this stuff takes almost 30 days to cure and dry,(i think my pic of me doing this is on petes website),but is tacky enough within 2-3 days and the tube can be reinstalled after this period,I had a talk with someone from the company that makes this stuff about 4-5 yrs ago..
I will mail out those coils on my post office day on weds to you..
good luck.!
terry

Thanks Bill and Terry. I have an NTE112 diode on order.

I have already performed the vacseal treatment on the CRT. It Seemed like an important thing to do.

The Tuner is all cleaned up and now I can tune a good picture looking with a scope at the input of the first video amp. Seems like maybe I will not have to touch the IF. I have not swept it yet. Next issue is that the color will not lock. I can get it to stabilize for a bit by turning the AFC balance control but then it will come unlocked again. Tweaking the AFC control again will bring it back to lock. The Hue control does seem to work but, looking at the scope, it looks like the hue is 180 degrees out, when it is locked. The reference oscillator appears to be working fine. I may not have much time this week to troubleshoot but I'll get back to it as time permits.

Once I get the cabinet out and the CRT installed, I'll post some photos. I am trying to get most of the troubleshooting and functional verification done before I put the chassis back in the cabinet.

[QUOTE=Tim]Hope everyone had a great Halloween. After the trick or treaters quit ringing the bell, I grabbed a Peanut Butter Cup and decided it was time to put some volts to the chassis.

Tonight was a meaningful night to do that as it was 50 years ago tonight that I, as a young trick or treater, saw color TV for the first time. I'll never forget when that lady opened her door and there in the living room was a huge wooden TV cabinet displaying a COLOR picture! (CT-100??) I don't think I even knew color TV was possible before that night. It was 10 years later when we finally got a color set.

Anyway, I removed the Horiz Output tube, plugged all of the coils and speaker, connected a few voltmeters and ammeters and started cranking the variac. I think it has been at least 15 years since this chassis had power applied. At about 90 volts I heard noise from the speaker and kept going to 115V. Voltages and currents did not seem out of line. I rotated the tuner one click and there was audio from the newscast! A little rotation of the fine tuning control brought it in perfectly. It is always a great feeling to have a set come back to life but this one feels better somehow.
QUOTE]

Hi Tim, That must have been some incredible moment to see that color set working as a boy. Did the lady invite you in to look at it? Do you remember what program you saw? Did you ever go back to see if the set was still at the house? Where did you find the set you have?
Thanks

I can get it to stabilize for a bit by turning the AFC balance control but then it will come unlocked again. Make sure the diode-connected half of the 6AN8's in the AFC circuit are good. I had one start okay but slowly drift into oblivion in a few minutes. The AFC circuit seems to be rather forgiving. That scope-based procedure where you balance a slowly varying dc level works unexpectedly well. I have made a nice video of it and will take a DVD of it to the next ETF convention. The AFC balance pot seems to be a bit of a nebulous adjustment though; I set it to center; maybe because the lock is so tight, there is not much affect when adjusted. Again, the AFC / reactance tube / crystal oscillator, etc. loop can be quite stable and hold the hue adjustment constant from day to day.

If the signal to noise ratio is low and the video is noisy (not 'fuzzy' as when the fine tuning is not properly adjusted) and the signal source is okay, and it happens on one or two channels, tweak the tank(s) in the mixer circuit in the tuner (the first adjustment hole is the LO, the rest are the mixer then the rf amp).

I can make immediate use of that second 6200uh/6700uh coil from Terry if you don't need it.

Pete

No time to work on the set today, thanks for the tips Pete. PM or e-mail me your address and I'll send you the coil.

Bobby:

Thanks for the comments and interest.
I think I went in the house for a minute or two. The man of the house was sitting in his easy chair but I do not remember what show was on, I just remember seeing the color. I may have seen the set again in subsequent years but my only memory is of the first. I have no idea what became of that set. The set I have now, I acquired through an ad on Steve's ETF site.