Today's Mystery Guest (RCA CTC-4)

[old_coot88]

Phil,
I know it's a long shot (well, so were the suspicions about the v.det diode), but see if you can locate the mixer plate adjustment. It may be a slug or a trimmer. Just tweak it slightly in both directions while watching a normal color program. Can't hurt nothin'.

In fact when we used to get tuners back from the rebuilder, there was a reminder tag stating to optimize the mixer plate coil if necessary.

[Username1]

Originally Posted by old_coot88

Phil,
I know it's a long shot (well, so were the suspicions about the v.det diode), but see if you can locate the mixer plate adjustment. It may be a slug or a trimmer. Just tweak it slightly in both directions while watching a normal color program. Can't hurt nothin'.

In fact when we used to get tuners back from the rebuilder, there was a reminder tag stating to optimize the mixer plate coil if necessary.

I agree with this as a first place to check..... If you have a tuner subber use it,
or since you have the ctc 11 sitting there with nothing to do...... Take off the
rca plug from the tuner into the if strip, parallel it to feed both sets.... That way
if running 2 IF loads diminishes the signal you will see it on the 11 also at the
same time..... And it keeps the agc intact for the tuner.....

Double check the long feed line by running it to the 11 first to be sure it is not
getting any loss or noise etc.....

Remember to check grounds..... No spark shows.....

.

[Phil Nelson]

Originally Posted by old_coot88

see if you can locate the mixer plate adjustment. It may be a slug or a trimmer.

The schematic shows trimmers and adjustable coils connected to pin3 of the 6X8 oscillator/mixer:



Some (maybe all) of those three trimmers may be accessible through holes in the tuner cage. I haven't found a diagram that shows all of that clearly. The Sams schematic does not show the adjustable coils (L42, L56)at all, and my photos of the tuner taken while cleaning don't show the internals clearly enough to guess whether they exist in my set.

Originally Posted by Username1

Take off the rca plug from the tuner into the if strip, parallel it to feed both sets

I was ready to run out and try this, when I remembered that the CTC-11 cable unplugs, but the CTC-4 cable is soldered on. I'm debating whether I want to unsolder it yet another time. It has already come off twice -- once for cleaning the tuner and again to lubricate the fine tuner when it got sticky.

Phil Nelson

[old_coot88]

Phil,
There is no mixer plate coil as there is in later tuners. Please scratch that whole idea. I should not have brought it up. Please don't mess with any of the trimmers or slugs, as they are strictly oscillator related.