My Brand New CTC-7!

[SwizzyMan]

Well it cant be the reactance circuit I recapped everything the whole underside of the chassis

[Bill R]

Why can't it be the reactance circuit? Caps are not all that's there. Could be a resistor, coil transformer, tube socket, etc. Just because the caps have been changed that is no substitute for troubleshooting. Sometimes other things are wrong.

[SwizzyMan]

The reason I say this is because most of the resistors I have tested on this set are barely off value.

[SwizzyMan]

OK. So what do you guys suggest I do? Check some resistors? adjust more coils? This project has been frustrating me lately and I would like to have it done by the time I start school which is Tuesday of next week. I am not looking for complete perfection I just want normal color on my color TV. At this rate I probably wont finish this before Tuesday next week.

[Electronic M]

Check Resistances (including those of coils and transformers) and voltages in the osc. circuit, and re-solder the tube socket.

Just because some resistors are good in one spot don't mean all of them are good.

[old_coot88]

If he's replaced the cap that parallels the reactance coil, he oughta double check that it's the right value, since it's critical.
Surprizin' nobody's chimed in about the crystal (or maybe I missed it).

[Phil Nelson]

Page 18 of the Sams manual has a resistance chart showing what resistance you should measure at each pin of each tube. It's worth spending a couple of minutes to check the resistances on the 6U8A tube and compare them to the chart. These readings involve more than individual resistor readings.

If you don't have the Sams manual, send me an email via http://antiqueradio.org/contact.htm and I'll mail it to you.

Phil Nelson

[DaveWM]

double check work done (cap values and connection points)
look for crossed wires (lead dress of parts on point to point)
check pin continuity of tube sockets to circuits
use sams as a rough guide on resistance (don't get too hung up unless dif are huge, there are lots of caveats on those, read the notes)

a new xtal is a good idea just to eliminate it as an issue, not likely but no real good way to test.

test equipment is the problem, with out a good scope you are hoping to find the problem. So it comes down to guessing based on observation.

Hard to say if the coil diddling could now cause a new problem. If it was mine I would do all the above report back findings and try a new xtal. I prob have one laying around here somewhere but will have to dig around to find it.

for now NO more coil adjusting until at least you do the above. then will prob have to try the procedures laid out for adjustment of the coils that have been adjusted, mainly peaking out the T704.

[SwizzyMan]

I have an RCA WO-33 scope is that suitable? I am just not very acquainted with scopes. What is an xtal?

[dtvmcdonald]

Its probably not the crystal. They seldom change frequency.
More likely are the 220 and 82 pF caps attached to it and
the15 pF cap across L704.

Also ... have you tried turning C740 (RCA schematic), noting where it
was originally set.

But as I said before, the next step is to try playing with the cathode to
grid voltage on the reactance tube and see how it changes the frequency.
Making a bias box is easy, just use a 9v transistor radio battery.

[SwizzyMan]

Should I just make videos of me doing all this?

[dtvmcdonald]

No videos ... just numbers!

Try measuring other circuit point voltages.

In particular: using an ANALOG voltmeter with a 10 meg resistor
between circuit and probe tip, not digital multimeter, OR
digital meter with the 10 meg resistor at the probe tip and 1
.01 uF cap from probe tip to ground, measure the following:

pins 1 and 3 of V706 (RCA) the 6BN8 phase detector and
pin 9 of V707 the 6U8 reactance tube.

Have you checked the resistance, disconnected from the circuit,
of R727A and R727B, attached to pins 1 and 3 of V706. These
REALLY should be within 1% of each other.

Try everybody's suggestions and carefully report back.

[Electronic M]

Radio Shack sometimes has TV crystals in store.

[DaveWM]

try this

find a channel that works where you adj fine tune fully CW until just losing sync or near just losing sync.

with reg programming on try adjust the horz hold to see if color will pop in.

[SwizzyMan]

Oh too late for that I pulled out the chassis. I tested r605 the 68K resistor and it is reading 65.5K.