Colortrak CTC120

[drussell]

I think mine is actually just a plain CTC-120 also, the SAMS just happens to be labelled A, perhaps it just covers some later revisions or something, although it doesn't even list my GJR641 in the 47 models it does list on the front page. Go figure.

The diagram pasted inside my cabinet says CTC-117/118/120

This SAMS covers a whole swack of models. For example, it includes at least 5 different tuner setups, 3 different ones with the LED display on the front, the one that uses the OSD and includes the clock and at least one mechanical tuner.

L201 Quadrature (13.6uH) part #143834

U201 part #153684 crosses to:
ECG: ECG1175
NTE: NTE1175
GE: GE-1175
RCA: SK3212/1175
Workman: WEP2175/1175
Zenith: 221-Z9056

An ex of mine once picked up a similar chassis, portable, mechanical-tuner model at a garage sale for a few dollars because the sound didn't work, thinking at worst we'd be using it directly off of a VCR to get remote capability and had a small stereo with aux input right there anyway. When I pulled the back and twisted the adjustment marked Audio IF or somesuch about 1/8 turn the sound came up perfectly.

That TV worked like a charm for years...

[drussell]

Troubleshooting - Audio:

If there is no sound, check the volume control voltage at pin 1 of Plug P302 while the volume is varied from MINIMUM to MAXIMUM. The voltage should vary from about 0.67v at MINIMUM to 6.17v at MAXIMUM volume. If the voltage is absent troubleshoot the Remote Receiver Board (MCR017A) and the Tuner Control Board (PW2500). If the volume control voltage is good, inject an audio signal at pin 9 of the Audio IC (U201). If there is no sound at the speaker, check the Speaker, Plug P201 and the voltages and components associated with pins 1, 2, 4, 7 and 9 of IC U201. If sound is now present, check the voltages and components associated with pins 10, 11, 12, 14, 15 and 16 of IC U201. Also check the Sound Take-Off Transformer (T301).

U201:
1 - 25.3v
2 - 12.3v
3 - GND
4 - GND
5 - GND
6 - N/C
7 - 2.05v
8 - GND
9 - 8.84v
10 - 4.12v
11 - 4.12v
12 - 6.14v
13 - GND
14 - 4.23v
15 - 4.23v
16 - 6.34v

Let me know if you need the audio chunk of the schematic.

[drussell]

I thought I would post the audio section schematic anyway, in case it helps:

[Edit: Interestingly the forum seems to have converted the uploaded grayscale .GIF to a .JPG]