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-   -   Deader than dead CTC-9 (http://www.videokarma.org/showthread.php?t=270868)

Tellyrescue 09-11-2018 08:23 PM

Deader than dead CTC-9
 
5 Attachment(s)
Recently acquired this RCA CTC-9 metal cabinet set, yoke is charcoal along with the horizontal width pot. Knobs are gone and the cabinet has a nice scar on top right corner.

Hope to get it glamed up and working as a daily driver.

Tellyrescue 09-11-2018 08:26 PM

5 Attachment(s)
More pics

bgadow 09-11-2018 10:08 PM

Great project-some real sharp repairs on that set! Proves that there were always hacks. Lots of fun to bring something like this back from the brink.

Penthode 09-12-2018 12:14 AM

I have a CTC 11 which was similar. It was great fun solving the problems. The if coils had disintegrated and found exact replacements at a nearby electronics surplus.

Patience and dedication will see you though! :thmbsp:

Electronic M 09-12-2018 12:25 AM

If the width pot is the one with the green wire and the brown half a lamp cord wire to chassis, and you judged it with your eyes instead of a multimeter then you may find that it still works...That one seems to use black plastic to hold the resistance material and terminals (instead of the brown phenolic of the other pots) and is likely still just fine.

The yoke is not so much charcoal as disintegrated plastic. The early plastics used for the outer shells on most yokes before the mid 60's were very unstable and will rot away on their own...This even happens to unused mint in box NOS specimens.

The windings and important core parts look fine and are probably still safe and functional. The shell can be recreated with a little effort with modern plastics. The part that usually rots away only acts as a mount for terminals as well as a guard to make it difficult for a service tech to accidentally grab those terminals with the set running (it also is supposed to be the grab handle to adjust the yoke).
You want to avoid touching the yoke terminals if the set is powered on...The meanest shock I've ever gotten from a TV set was a CTC-15 clone that I touched a portion of the yoke winding where the insulation was bad...That is the only time I can remember my 'let go of this' reflex kicking in full strength...

Tellyrescue 09-12-2018 10:11 PM

Quote:

Originally Posted by Electronic M (Post 3203866)
If the width pot is the one with the green wire and the brown half a lamp cord wire to chassis, and you judged it with your eyes instead of a multimeter then you may find that it still works...That one seems to use black plastic to hold the resistance material and terminals (instead of the brown phenolic of the other pots) and is likely still just fine.

The yoke is not so much charcoal as disintegrated plastic. The early plastics used for the outer shells on most yokes before the mid 60's were very unstable and will rot away on their own...This even happens to unused mint in box NOS specimens.

The windings and important core parts look fine and are probably still safe and functional. The shell can be recreated with a little effort with modern plastics. The part that usually rots away only acts as a mount for terminals as well as a guard to make it difficult for a service tech to accidentally grab those terminals with the set running (it also is supposed to be the grab handle to adjust the yoke).
You want to avoid touching the yoke terminals if the set is powered on...The meanest shock I've ever gotten from a TV set was a CTC-15 clone that I touched a portion of the yoke winding where the insulation was bad...That is the only time I can remember my 'let go of this' reflex kicking in full strength...

I measured the component out of circuit and it will need to be replaced as the carbon track is ruined.

irext 09-13-2018 07:25 PM

I am fairly certain that yoke is cactus. A ring test should prove it. I've seen yokes looking like that before and they were all crook with shorted turns.

Sparky 09-14-2018 01:57 PM

Working on one right now. Bad Bubblebees in the horizontal circuit. Nasty things that they are.
Dump the Black Beauties as well, and of course paper.
The set is like new now. Not to rub it in, just to say I feel your pain. Pix to follow...

Sparky 09-28-2018 11:27 AM

The 106305 Deflection Yoke is a Y-107 according to my 1983 Thordarson TVPG-15 book. The Sams 459, page 11, doesn't cross it.
Check the horizontal centering pot on the flyback and the brown dipped caps in the vicinity, as well as the 56pF 6KV disc.
Mine were all off and leaking. The current went way down after replacement.

Tellyrescue 09-29-2018 08:24 PM

Quote:

Originally Posted by Sparky (Post 3204411)
The 106305 Deflection Yoke is a Y-107 according to my 1983 Thordarson TVPG-15 book. The Sams 459, page 11, doesn't cross it.
Check the horizontal centering pot on the flyback and the brown dipped caps in the vicinity, as well as the 56pF 6KV disc.
Mine were all off and leaking. The current went way down after replacement.

Good tip on the disc, never though to check it.
I had to replace the horizontal width pot as the fine wire was all tangled up inside and believe it shorted out taking the resistor on the back of it and the horizontal winding on the original yoke with it.
I also replaced the two caps in that area. I now have HV but it needs to be reduced.

Tellyrescue 09-29-2018 08:29 PM

3 Attachment(s)
Progress so far;
HV is 29+KV and turning up the horizontal makes it go higher.

Chassis is back out for resistor checks and cap replacing
Starting with the horizontal board and vertical board

bgadow 09-29-2018 08:46 PM

Yep, looks like you're on track (sorry, couldn't resist!) Here most folks have trouble with HV being too low...

Electronic M 09-29-2018 09:14 PM

May want to get the HV reg working first. If you run it that high too long you may damage the CRT and or flyback with internal arcing.

timmy 09-30-2018 04:53 PM

Wow that seems like run away hv,+29 kv if the fly can put that out it should last a while provided it is lowered.

Tom9589 09-30-2018 08:21 PM

Timmy, when you adjust the HV down to 25K, you will actually be putting more load on the flyback. Remember, the total load on the flyback is the sum of the current drawn by the CRT and the current drawn my the HV voltage regulator. As the scene on the CRT gets brighter, the CRT draws more current while the voltage regulator draws less and vice versa. The whole idea of shunt regulators is to present a constant current load to the flyback/HV rectifier under all screen brightness levels.


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