CTC-17 Screen control issue - Videokarma.org TV - Video

freakaftr8 · #1 11-13-2009, 12:48 AM

Hey guys,
I picked up this CTC-17 combo last month and after changing like darn near every tube in the set as it seems it was a high use set I got HV and accompinied by a bright green raster, after replacing a broken wire I have barely any blue screen voltage. The CRT is good but I have been looking at the chassis and I cannot seem to figure this one out.. Any ideas?
Thanks!

ctc17 · #2 11-13-2009, 11:59 AM

Did you have the sams on this one? I will take a look when i get home and can scan it if you need.

freakaftr8 · #3 11-13-2009, 12:31 PM

Oh yeah I have a sams. I had to repair the CRT socket. Bad corrosion and some arcing on the focus pin. Thought this might have been an issue as well but it's not. If i pull the B/Y 6GU7, I have good blue screen drive voltage. Max should be 177v. I get about 70v, green and red max around 177 to 180v. Im suspecting im looking over an out of tolerance resistor somewhere.

ctc17 · #4 11-13-2009, 06:51 PM

Any chance the crt is leaking and loading that voltage down? I would be interested in seeing a picture, I bet we have almost the same exact combo. Mine has a really good picture better than my Zenith sets.

freakaftr8 · #5 11-13-2009, 10:46 PM

I know these 17's put out an amazing picture! Dont think the CRT would be an issue, I get full voltage to the CRT when I pull the B/Y 6GU7 amp

ctc17 · #6 11-13-2009, 11:31 PM

I would be interested in the voltages on pin 6, 7 and 8. If c140 was leaky that could do it for sure. Or if r198 had gone way up in value that would do it too. With the tube plugged in I would 'feel' r198 to see if its super hot like the tube is biased on and loading the resistor down. If r196 were open I suspect it could cause the tube to bias on load that voltage down too.

For some reason someone circled that resistor on my copy of the sams.....

freakaftr8 · #7 11-13-2009, 11:35 PM

Ok here's something else.. I just checked the HOT cathode current... 112ma?? Thats low and I bet this is a cause of the excessive wax all over the bottom of the chassis

Here are pics

ctc17 · #8 11-13-2009, 11:41 PM

All 3 of my rcas have wax. I dont think I would stress that. That is kinda low though but I dont see how it could effect this blue drive thing unless the 400volt boost was low for some reason. That almost seems like a false measurement.

Have you checked the hv on the crt?

freakaftr8 · #9 11-13-2009, 11:42 PM

This is my first one.. Got this one in November 2008

And here is my CL find in downtown Sacramento. This is the one im talking about..

freakaftr8 · #10 11-13-2009, 11:46 PM

Hmmm, im going to check my filters.. Good call! It just seems that this one has an excessive amount of wax, my other 17 (the first one in the pics) has no wax droppings at all..

I always thought that the rule of thumb was if you have too high current on the fly it will overheat and damage it and the same goes for too low current as well. my other 17 is around 208ma (which is pretty good as current goes).

Quote:

Originally Posted by ctc17

All 3 of my rcas have wax. I dont think I would stress that. That is kinda low though but I dont see how it could effect this blue drive thing unless the 400volt boost was low for some reason. That almost seems like a false measurement.

Have you checked the hv on the crt?

ctc17 · #11 11-13-2009, 11:51 PM

Mine looks different. Someone cut the legs off mine long ago this is and issue because it cant get air up through the bottom. I put a muffin fan to take care of that though.

I have 2 of these with the rca tuner and I have never been able to get the stereo multiplexer aligned right. If I get it aligned to where the separation is correct the noise floor is so high its annoying. I can get it half way in between but its fake stereo.

The Zenith receiver seems superior and the rca tv seems superior to the Zenith. Maybe a mashup is a good idea... ok Im off topic here.

freakaftr8 · #12 11-13-2009, 11:58 PM

I know what you mean about the multiplexer. This new ctc17 I have seems to have that same issue. It's the 800 series. It seems to have more right channel output than left.. All in good time. At least the stereo works.. The one on the other 17 wouldnt work right. I replaced all the outputs and it worked fabulous! It's the 400 series.

freakaftr8 · #13 11-13-2009, 11:59 PM

Hey ctc17, post up a pic of your set, with or without legs, im sure it's nice

ctc17 · #14 11-14-2009, 12:03 AM

I have a cell phone that has an fm stereo transmitter in it. I made an mp3 that plays in the left channel only for a few minutes then the right only for a few. The sams gives and alignment procedure for using a strong fm signal. I can get the separation right but its totally noisy.
Come to think of it I cant thing of any tube multiplexer I have seen that worked real good.

The receiver im mine totally died now.

Its NOT nice! Its poor and even has cigarette burns in it. I found it on the curb in the hood. Give me a few let me get a pix..

Charlie · #15 11-14-2009, 06:41 AM

Freak, I have a 15 that had issues with that bright green screen. Turned out one of those 6GU7's just wasn't seating good enough in the tube socket.

Just curious... what kind of line do you get when you slide the service/normal switch to the service position?