My Brand New CTC-7!

[SwizzyMan]

Adjusted the one by the HV fuse and the 6U8 color oscillator.

[DaveWM]

try subbing a burst amp and phase detector tube. sounds like the reactance circuit is not working.

[DaveWM]

you are going to end up looking at pin voltages, so you need to start looking for some tube extenders with test points. Check your local tube guy, you will need to get some 9 pins, get some 7 pins too as they come in handy.

[SwizzyMan]

Was only able to replace the burst amp. Color bars are rolling a lot faster and arent as bright.

[DaveWM]

try adj L704 with the new tube. see if there is any change in the number of bars as you adjust.

[SwizzyMan]

it goes from 4 bars to 5 bars.

[dtvmcdonald]

A note about measuring voltages on flaky oscillators, which yours is.
No matter what type voltmeter you use, old VTVM or modern digital multimeter,
do NOT attach the probe directly to the circuit! This will load it down with
lots of capacitance.

Find out what the meter resistance is, usually 10 megs. Do this by measuring
a suitable voltage source like B+ with the meter, then through a 10 meg resistor
attached to the probe end. If you then measure half the voltage, its a 10 megohm meter and you make measurements with that 10 meg resistor on the probe end and
double the number. If its not a 10 meg meter, you need to calculate the correct
correction factor.

[Electronic M]

Originally Posted by SwizzyMan

it goes from 4 bars to 5 bars.

Adjust it the other way and try more turns. Also if it is a PCB mount socket it may be prudent to touch up the socket solder joints.

[SwizzyMan]

OK did 2 turns and now have 3 bars of rolling rainbows.

[Electronic M]

Keep going until you have chroma synch, the number stops decreasing, or it runs out of threaded range.

1/2-3 turns is not always enough to synch a chroma osc.

[SwizzyMan]

Originally Posted by Electronic M

Keep going until you have chroma synch, the number stops decreasing, or it runs out of threaded range.

1/2-3 turns is not always enough to synch a chroma osc.

Turned till it wouldnt go anymore on both sides. It goes away when I rotate it to the right completely. No color the bars are all purpleish

[SwizzyMan]

I think T704 might be causing this. I think I adjusted it a lot more than I thought.

[dtvmcdonald]

If you adjusted the top slug of T704 no harm was done as long as it
is as the manual describes it. (Some similar transformers were made
at one time upside down.)

Try grounding the grid of V-707A and see what happens. Try connecting it
to a battery source of 0 to -9 volts (pot across a battery) and see what happens. Try connecting it to its own cathode through a 100k to 1 meg pot and see what happens as the pot is varied.

If this does not make it go through "no bars, just unstable" then its
the oscillator or reactance tube circuit. That's if you managed to get L704 roughly back where you started.

[SwizzyMan]

Is the reactance circuit located under the chassis? I recapped everything.

[Phil Nelson]

Yes, it's under the chassis. The 6U8A tube (called V707 by RCA or V20 by Sams) actually handles two circuits: the 3.58-MHz chroma oscillator and the chroma reactance control (aka "chroma reference osc control" in the Sams manual).

Phil Nelson