My Brand New CTC-7!

[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.

[SwizzyMan]

So, should I replace it?

[Electronic M]

It is only 4% off if my beer intoxicated math is right. Most resistors are 5 to 20% so unless it has some special labeling saying it should be 1-3% leave it be.

Give a man a fish feed him for a day, teach him to fish feed him for life....Now for a teaching moment. The fourth band on a resistor is tolerance. None=20%, silver=10%, gold=5%...There are others IIRC but not commonly seen in tube gear. Multiply the face value by .2, .1, .05 respectively depending on marked tolerance. If the measurement is larger than face value add the product you just calculated to the face value if smaller subtract. If you added and the measurement is larger than the sum replace, if you subtracted and the measurement is smaller than the difference replace, otherwise keep the original in circuit. Next time you need to know if you should keep a resistor do the math first.

[SwizzyMan]

OK so it is only 4% off out of 20% so it is fine. Well then. What is causing my terrible horizontal lock then?

[dtvmcdonald]

Its impossible to say what's causing it until it is fixed!

Whatever you do, don't give up. These things can take months.
Learn to use your scope and take pictures of it so they can be posted here.

I've got 55 years of experience and it took me weeks to permanently fix
the horizontal in my CT-100. And I have several scopes I could and
did hook up all at once.

How does the lock vary with signal strength?

[DaveWM]

so the horz lock is a problem now? I thought you had it so it would stay locked with 1/2 turn either way?

fyi, as long as you are having horz sync is issues its pointless to work on the color sync, they are related. You need to get the horz working 1st.

[DaveWM]

IF we are back to horz lock issues, a few things to consider.

AGC, keyed agc is always good for tough dogs. Make sure you check C405 a
.22 uf cap used to filter the AGC.

Note where the AGC pot is set (top of chassis near the chroma section). when having lock problems try adj just a bit if no improvement put it back to the starting position.

the deal is if the AGC in noisy or incorrectly set (cap or pot setting) then the IF amp gets whacky and does odd things with the signal, clipping etc..

this results messed up sync signals (they are the 1st thing to get clipped in the IF amp).

The normal approach to checking this would be to attach a bias box to the AGC line and manually provide the bias needed for the IF amp. Since you don't have a bias box we have to assume the most likely suspect (after the tube) and go right to the AGC filter cap.

An alternate to the bias box is a scope on the agc line set to read DC. adjusting the pot should raise or lower the DC bias from the output of the AGC supply AND the voltage should be clean DC with no "grass". the grass is a result of the loss of filtering.

I presume you have replaced the C405 in on of you mass recappings already so this may not be an issue.

Another possibility again assuming you are still having issues with horz hold and the issue is a very critical hold range of the pot (only a few degrees of adj from flopping one way to sync to flopping the other (which is NOT what you have described so I only mention for future reference) is the 68k resistor that p's with the horz hold coil. I presume its a Q killer to soften up the peak of the coil.

[SwizzyMan]

I do believe I did replace the agc filtering cap. The horizontal lock has gotten progressively worse with now less than a quarter turn on both sides to lose sync.
Will probe around with a scope and make a bias box.

[DaveWM]

just for fun try this a quick and easy thing.

find the 68k resistor on the horz board, read the value, it should be very low prob in 10's of ohms since its connected across the horz adj coil.


Once you have found that resistor, connect up one in parallel another 68kish will be fine. See if that has any effect on the horz hold control, you want that to be a lot broader of an adjustment. Just use some jumpers to hook it up, no need to break out the soldering iron or remove anything. Be careful when using jumpers, you don't want to short out anything.

[DaveWM]

this is generally the 1st thing I do if I think the sync is an issue.

Note this assume the osc is not the issue (can flop both ways)

Note the use of tube socket extenders so work can be done from above with the set on.

watch this to better understand the function of the sync separator.

https://www.youtube.com/watch?v=Flg5LwBadHI

[dtvmcdonald]

How did you get the probes to stay on the extenders?

The ones I got are fiendishly designed to make this impossible.

[DaveWM]

indeed, I remove the sliding hook thing and generally just rely on the prob pin stuck in the hole of the extender, its pretty iffy but generally I can get them to stay put.

[SwizzyMan]

OK thanks to both of you for the ideas. Going to take a short break on this set until Monday. Will try all of your suggestions then.

[SwizzyMan]

Alright I think I am ready to start back up on this TV and finish it once and for all! Would do any of you recommend me doing? I did get some 9 and 7 pin test sockets (thanks to Dave for alerting the guy at the tube store near me).