My Brand New CTC-7!

[Phil Nelson]

The controls are identified on page 24 of the factory service manual.

The color killer ("killer threshold") control is inside the Contrast control shaft. Pull off the Contrast knob and use a thin screwdriver to adjust.

Phil Nelson

[SwizzyMan]

OK my only problem left now is for the first 10-15 minutes of operation everything is out of focus. After about 10-15 minutes it fixes itself and is relatively clear. What needs to be done?

[old_tv_nut]

Does it suddenly jump into focus, or get there gradually? I presume the focus control does not have enough range to make it sharp when you first turn it on? If the change is gradual, it may be a tube.

[SwizzyMan]

It is gradual from what I think I see. It slowly comes into focus.

[DaveWM]

you can try replacing parts OR you can try to figure out what is going on.

parts would be the resistors/pot/tubes in both the focus/HV regulation.

that's a lot of parts, and you risk taking a working set and making it not working from needless stress of part changing.

OR to figure out what is going on, use the HV prob and check the focus voltage from startup until focused. See if its changing and which way is it going (up or down). if no change in focus voltage yet change in focus on the screen then monitor the HV the same way, from startup blurry to focused and see if its changing. These are non invasive checks not likely to hurt anything.

after you find which voltage is changing effecting the focus, then you can diagnose the circuit.

I have an idea where the problem is but I prefer to withhold that to prevent unneeded part replacement. The voltage checks would confirm.


if you want to try one quick thing go for the obvious, focus problem, focus tube, that is what the tube jockeys did back in the day.

[Zenith26kc20]

Look for corrosion on the focus pin on the picture tube and in the socket itself. My CTC9 had this problem and cleaning the socket cured it.

[DaveWM]

Originally Posted by Zenith26kc20

Look for corrosion on the focus pin on the picture tube and in the socket itself. My CTC9 had this problem and cleaning the socket cured it.

good point, Sometimes the corrosion will follow up the wire.

[stromberg6]

Originally Posted by DaveWM

good point, Sometimes the corrosion will follow up the wire.

DITTO! If that doesn't work replace the 1V2, and see if it helps. Also check the socket connections on the 1V2 socket. Had corrosion on the CRT socket of the CT-100 I was once steward of, and the focus behaved in a similar way. I did wind up replacing the HV wire from the socket to the 1X2 base (CT-100), so it did follow up the wire a bit. Cleaning the socket and CRT pins also helped.
Hope this helps!
Kevin

[SwizzyMan]

Also just noticed there is this really annoying hum coming from the speakers whenever I try to watch TV on the set. I can barely make out the sounds from the programming over the humming. I tried messing with the fine tuning and trying different channels on the TV. Can't get it to go away. Also know the picture is very clear but the humming is the only bad part. Also the humming gets VERY loud when text appears on the screen. What is going on with my tuner? It never did this before.

[MRX37]

My guess, a filter cap or something with the audio circuit.

[Electronic M]

If the hum is only when receiving a signal, then it is an effect of the signal and not the power supply filtering. It will probably be worst with high contrast/fine text on the screen. There are a number of causes for it. A predominant one is video over modulation....The audio is FM the video is AM...when AM over mod occurs it also inverts the FM carrier and this shifts it's phase by 180 degrees (a form of phase modulation). FM and phase modulation are so closely related that a detector for one will receive the other (and vice versa) with an integral or derivative operation preformed on the recovered modulating signal.
This PM audio carrier distortion becomes an annoying buzz when demodulated. The only solution is to turn video modulation down (if you have a modulator that supports this such as a blonder tongue AM series), or get another modulator.

There is also the potential of audio misalignment. which can accentuate this effect on some sets.

[old_coot88]

Tried adjusting the AGC?

[SwizzyMan]

Feeding a signal through the BT modulator that fixed the focus and the annoying hum. It was over modulating that is what was causing it. Only thing left is that annoying yellow discoloration on red based colors. This happens only in the bottom right corner of the CRT face. Like I said I have degaussed this set multiple times. It is mostly noticeable on red colors and orange basically any red based color. Is this edge purity issues?

[tvcollector]

Sounds like purity.. Did you do purity set up, doing red first? Sometimes it may be where you have the set sitting.. It's happened to me before..

[SwizzyMan]

Ive done purity in all the ways possible except for the edge purity. I can't seem to get a full red screen when sliding the yoke forward while doing a regular purity.