'76 25" RCA XL100 CTC78 console - Videokarma.org TV - Video

radiotvnut · #1 07-29-2008, 08:35 PM

My friend that gave me the '81 Magnavox came through today with this '76 XL100. This uses the CTC78W1 chassis, probably the last upright RCA chassis. I think the CTC68 was the newest upright chassis that I've seen. This set uses those pesky slide controls for tint, color, etc. The CRT was almost toast but responded to the clean & balance feature of my CRT tester. I've got audio and a raster with retrace lines that does not change as the brightness control is turned. Sounds like I need to troubleshoot the video circuit.

I used to see many of this style chassis back in the '90's. This is the first one I've had in several years. They are about to become non-existent, like all the other once common TV's.

sampson159 · #2 07-29-2008, 09:23 PM

try cleaning the service switch. had same proble with my ctc68 i got at the early television museum auction. even though was was a new in box set,it had many issues. tuner was filthy,service switch was dirty and all the controls needed cleaned. these are truley rca s best solid state sets.very reliable and good,crisp picture.close to a zenith chromacolor in my opinion. i am using mine as a watcher while relaxing in my barber chair,(yes bryan,i did finish it!) good score and enjoy it!

radiotvnut · #3 07-29-2008, 10:01 PM

I'll bet this set would really look good with one of those Sylvania black-face CRT's! I'm sure those are darn near impossible to find now.

The guy that owned this said that about ten years ago, his Dad was watching a ballgame on this TV when the picture suddenly went off. He got upset because he was missing his ballgame and quickly went and bought a new TV and rolled this one into the back room.

I will clean that service switch and the module contacts and see where that brings us. Fortunately, I do have a Sams on this set incase I have to go deeper.

BTW, who remembers the XL100 chassis that replaced this one? There was a CTC8? for the 19" sets and a CTC9? for the consoles. The chassis was flat and had several modules that plugged into the chassis. There was an MDR regulator module off to the side that RCA claimed was unrepairable. Those were still decent sets; but, not nearly as well built as the older XL100, IMHO.

bgadow · #4 07-30-2008, 12:28 PM

CTC-92? I think that was the one I tinkered with last year. Finally gave up on it due to problems with that regulator module. I wasn't overly impressed by it. I don't think I ever had an RCA console from the mid-70s but I had some good table models. One was, I think, a 21"-kinda odd, whatever it was. I seem to recall it being from '75.

wa2ise · #5 07-30-2008, 12:50 PM

Quote:

Originally Posted by bgadow

CTC-92? I think that was the one I tinkered with last year.

I'm drifting off topic for the moment here, but I had a CTC 101 set, the one with the comb filter. And the infamous bad flyback, the one with segmented high voltage windings with diodes between some of those windings. They first did 6 segments, and six diodes, but they tried to cheap out with just 3 diodes. The dynamic "AC" waveforms were too much for this design, and it would blow up after a while.

The yoke was interesting, in that the horizontal windings were "hot chassis" but the vertical was "cold chassis". The horizontal output circuits functioned as the set's switching power supply, with isolated outputs.

Aside from the bad flyback, this set had a great picture, I'd like to find another sometime (my old one got tossed when it died). If I had room, that is...

rcaman · #6 07-30-2008, 02:00 PM

i sold a lot of those ctc101,s every single one had a flyback go bad. BUT rca did warranty them for 2 years and the replacements never failed with me. and those sets had a hell of a picture on them. steve

radiotvnut · #7 07-31-2008, 03:25 PM

I've solved the video problem on the CTC78. There was no 240V going to the video output circuit due to an open R105 (180 ohm, 1 watt). R106 (18 Kohm, 1/2 watt) was also burned open. I'm sure this was due to excessive current being drawn through it when R105 opened.

Now, I've got to clean (if that's possible) those slide controls. They are hard to move and very touchy when they do move. I've never seen those slide controls on an RCA that actually worked right. Whoever came up with those needs a good butt kicking.

There is also an electrolytic going bad in the power supply. I can see a slight weave moving up the screen and there is some very slight pulling in on the sides that changes as the weave moves up the screen.

rcaman · #8 08-01-2008, 08:35 AM

if that capacitor opens or shorts i have seen it take out the scr,s for the horizontal deflection more than once. those are one of the best sets rca ever made. i have my grandmothers she bought new in 1976 it is a larger cabinet and in the maple finish. the tube is weak and i have a new rca to install one of these days. it was only serviced once needing a new tripler.

rcaman · #9 08-01-2008, 08:36 AM

Quote:

Originally Posted by rcaman

if that capacitor opens or shorts i have seen it take out the scr,s for the horizontal deflection more than once. those are one of the best sets rca ever made. i have my grandmothers she bought new in 1976 it is a larger cabinet and in the maple finish. the tube is weak and i have a new rca to install one of these days. it was only serviced once needing a new tripler.

mine also has those darn slide controls

andy · #10 08-01-2008, 09:46 AM

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wa2ise · #11 08-01-2008, 12:09 PM

I had a CTC62 IIRC that had the SCR. Still have some of the modules if anyone needs them.

radiotvnut · #12 08-01-2008, 01:18 PM

I really need to replace those slider controls. The contrast control is almost inoperative and they are all flaky and hard to move. I hope I can find something more substantial that will fit on the PC board.

I also noticed that the blue convergence is way off. Time to troubleshoot and/or adjust the convergence circuit.

RCAman, thanks for the warning concerning the cap taking out the SCR's. That will be my next order of business before I go any further. I noticed that when I turn the set off, I hear a faint "chirp-chirp-chirp-chirp" that sounds like it's coming from the horizontal circuit.

Kiwick · #13 08-02-2008, 10:06 AM

we have a LOT of 70s sets with thyristor line output stages here in Europe...

when restoring a set with a thyristor line output you want to resolder the entire line output stage carefully anc check the large mylar/poly capacitors for bulging and test them if possible, as failures in a thyristor line output stage can destroy the set and pose a serious fire hazard

radiotvnut · #14 03-19-2009, 04:25 PM

I dug this set out and decided it was time to finish it. The 300uf,200V section of the main filter was open; so, I pulled a 330uf200V snap-in cap off of a newer TV chassis, unsoldered the old section, and wired in the good cap. I then touched up the CRT bias and drive controls, the convergence, and the vertical size control and it now has a decent picture. Those slide controls are still touchy; but, I'm leaving them alone. Unfortunately, I'll probably have to let this set go as I'm out of room. It will probably either be sold cheap, given to the SA, or given to a needy person who is not too stuck up to own a 33 year old TV without a remote. I'll post some pictures as soon as I get my hands on the camera.

zenith2134 · #15 03-19-2009, 04:32 PM

How's the CRT holding up?

I wouldn't mind watching that set at all...Nice RCA's from this time are getting trashed at an alarming rate, which is unfortunate. The mid-70s to early-80s RCA's have been some of the best sets I've come across.