"Old Sparky" (CTC-31)

[Bill R]

Those voltages are all way high. It's late I will have to think about that one. I never ran one with no yoke and the HO tube out. Well I did run one once with out the yoke, but it burnt out a diode in the yoke circuit because there was no load. That was not a 31 though. I have a test jig to connect the chassis to, so it has the proper loads on the Horiz and vert. sections. The collector is connected to the grid of the blanking amp and to the grid of the horiz out tube through r143. It's late but it looks like you would have to have multiple componant failures to have the collector and base voltage so close. Like I said I will have to think about it some more. It will probably be something simple we are all overlooking. That's how my luck has been lately.

[bgadow]

Okay, progress, for the most part. What I found was that the set was living up to it's nickname-still more arcing! Very light, across a trace, only visible when it was darker in the room. More 'scrape, scrape, scrape' and when I was done the voltages @ Q1 were normal! I don't know, something must have gotten on the traces or something odd because since then I have found 2 or 3 more that want to spark over! I ran it earlier today all hooked up (with hv) and it worked okay (no color) but shut it off when I tracked down an arc; later I ran it for an hour or so without any problems, then once again a real bad arc-over, in another location, this one was bad enough to kill the raster before I hit the switch. Out the chassis came again, more scraping & cleaning. If I can get beyond this I can tackle the color problem; with some adjustment I was getting some color, odd in that pure reds (like a red dress or lipstick) show up great but fleshtones and most other colors are very weak. Same basic problem I had before the shorts started. I'll be trying again soon, and if it holds without arcing I'll try aligning the colors.

[bgadow]

So much for being on the right track. After carving out another arcing trace I put the chassis back for the 48th time, now sparks from yet another location! What is going on here!? This time I cleaned that new trace out, then also pulled open the hv cage to look for signs of trouble, but everything looked okay. When I again fired it up, more sparks, plus when the hv came up there was a hollow sound echoing, I couldn't see the screen from my position but I don't think there was a raster ecept for maybe a flash. I reseated the hv cage cover (this is the one with the 3A3 attached to the top cover upside down) in hopes that the connection was poor but no luck.

I am about to just put the back cover on and let it sit for awhile-maybe a long while! (it took several ordeals like this, with years of sitting in between, to figure out my CTC-5!) There are some other options:

A) Anyone wanna clean CTC-31 remote set, good project for ya?

B) Anyone gotta less finicky CTC-31 chassis gathering dust?

C) Anyone know whats going on with this thing?

Guys, I do appreciate the help you've given me.

[andy]

I would say that either there's way too much voltage on the board, or the board has been contaminated with something that's causing it to break down under normal voltage. I would try thoroughly cleaning the board all over with alcohol. Arc over isn't a common problem with circuit boards. I've only seen a few cases in many hundreds of TVs and monitors I've worked on and they were always in one islated part of the board.

[bgadow]

I tried to get a measure on the 355v line the last time I powered up but it was arcing too much so I had to shut it down. When it was behaving the bw picture and audio were great; seems like that would not be the case with a very high over-voltage? The arcing has occured only on the chroma board, but basically from one end to the other. I've swabbed much of it with rubbing alcohol, though I wondered if maybe that would leave something behind-I don't really think so, since the bad areas that creep up don't follow with where I have just cleaned. I can't see the flyback in action with this set, but could a bad one be introducing spikes that would cause this? Another strange thing, it never trips the breaker. Oh, well. I'm bringing home another roundie next weekend, my luck with them has been much better! (famous last words)

[Chad Hauris]

Try disconnecting leads from the B+ supply branches at the filter caps till you find one that stops the arcing. Remove h.output tube & damper so you don't overload it if the oscillator gets disconnected. Check the voltages at the caps once you disconnect the B+ lead that stops the arcing.

Also...
It sounds like you have an intermittant somewhere if you had a period with no arcing...maybe there is a ground connection to the circuitboard that has come loose? I had a condition of no horizontal oscillator in a CTC-38 that I tracked down to a loose solder joint on the B+ supply to the osc. Check the joints on the chroma board for microcracks, check them with an ohmmeter/continuity checker, resolder any suspect connections.

[Bill R]

Well all the arcing would explain the odd voltages. You may have to find another set to get a replacement board. The color problem you indicated when it was working could point to the demodulator circuits which are also on that board.

[bgadow]

I honestly had given up but the latest suggestions, especially Chad's idea to disconnect leads, made me pull it back out. And, what can I say: now it won't act up! One little spark when I tried it with hv and nothing else. I ran it an hour without problems and then last night I ran it from 8-midnight. Was it some loose or close wire that I moved away? (or component?) Or maybe just dumb luck? I'll keep my fingers crossed-I know chances are good it will come back. I tried pushing on the chroma board to see if it would act up, but I admit I didn't push very hard-I hate to look for trouble!

With the set acting right I set to work on the color problem. I did a quick setup )purity, basic convergence) & came up with a very nice bw picture. Tuning the station until the video was shot got me color but I couldn't get color on a decent pic. The IF coils had plenty of "screwdriver drift" to begin with so I stirred the pot even more. I did finally find a way to get a real, full color picture, though its not right: tune in a strong station just right, turn the agc a little too far into overload, adjust the coil in front of the 6KT6 (?memory?) and, voila, color, overloaded, but color. Well, I admit I'm in over my head when it comes to correctly aligning the IF. I can handle the ACC, etc., and right now all I've done is turn the coils until the color (when its there) stays put and is correct. It is encouraging to see that the set can produce a color pic if it wants to. Now if I can just make a color pic when I want it to! The bw pic when properly adjusted is very strong so I really think this baby could give a great color picture if I can work the bugs out.

(note: all 6GH8's are NOS GE tubes)

[Chad Hauris]

Does the no color problem re-occur when you turn the set back on after having adjusted it to produce color? May be a thermal condition...you may want to try the freeze spray on IF and chroma components. If it were an alignment problem only, once you aligned it to produce color it ought to stay that way.

One thing I have read is that low RF or IF gain on account of weak tubes can make color reception difficult. It says if you don't see snow and hear strong white noise with the antenna disconnected, you may have trouble getting color. How is the voltages at the IF and tuner stages?

How about your transistor stages on the chroma...have your voltages there returned to normal?