Quote:
Originally Posted by bgadow
Fixing up old tv sets is a constant learning experience and challenge for me. No professional training here, just what I have picked up from years of tinkering, and moreso, what I glean from here and the ARF.
Right now I am working on my CTC-5 (Deluxe chassis) which had a couple issues I had put off fixing. Figured it would be nice to have this one in tip-top shape for the digital switchover. An issue since I got it going: close interaction between the horiz hold/contrast/agc/brightness controls. Any of them can throw the horiz (and sometimes the hv) out of whack. I decided it was time to get serious about this. To start with, my best picture was looking pretty washed out. Tubes, including the crt, are good; I checked hv and it was hovering around 17kv, about 3kv too low by my references. By tweaking the front panel controls I can get a better pic, corresponding with a dead-on 20kv, but it is unstable, tends to jump out of sync or overload.
I have a pretty good library of TV repair books (including color TV) so I dug through them but I haven't found anything that addresses horizontal sweep alignment on these sets. Sams lists a brief set of setup instructions which says to adjust the horiz waveform so that the rounded and sharp points on the waveform are at an equal height, and it shows a picture of the proper wave. (I'm not great with a scope, but am working on it) I can get close but not exact. If I get the 2 peaks even I lose most of the valley; this is at the end of the coils travel and also makes the horiz unstable; it is prone to jumping out of frequency, so much so as to push HOT cathode current way over the line. I have expermented with various combos of waveform/horiz hold position. I would like to read more about this circuit but only the brief write-up in the Sams fits this chassis. Newer books cover the CTC-12/16 well but don't go back and hit the different circuit used here. I actually have some CT-100/21CT55 era stuff but it's no help, either.
Did the factory service manual for this set cover it very well? What might I need to do to correct that waveform? The horiz osc board has been recapped. I had replaced the coil bypass cap with a .015 when it should have been a .01, but have now corrected that. Any advice is appreciated. This set has a lot of potential and I'd really like to see it reach that higher level.
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Did you replace the mica caps? If not then you should start there.
I have a rca field service manual and the caps are listed as c605-12pf, c611-82pf, c610-82pf, c606-330pf, c604-1000pf. After you replace the caps do an alignment. The horz osc on the five is vary stable and you should not have to adjust it again unless something fails.
Good luck, The rca ctc5 is a cool set.
Ed