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Old 10-18-2014, 03:50 PM
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1963 RCA CTC-15 roundie

Acquired a CTC-15 from a VK member here. It's in great shape and produces a nice color image.

Two questions:

1. After about 3 hours of operation, the color fades out to near nothing with a green tint. This does not happen gradually, it will be fine and then just loose the color all at once. Cannot bring back the color by switching the channel selector, fine tuning etc. After maybe 5 or 6 hours, if I turn on the set, it will be fine with great color image again. What should I check first?

2. The set is 100% original, so only plan to show it to guests that visit and watch vintage TV shows on DVD. What is best, leave the set plugged in or unplugged? Is there a trickle current in the set when plugged in?
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Old 10-18-2014, 04:01 PM
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Well--the first thing I would check is to see if the 3.58MHZ osc. is running--when you lose color. It most DEFINITELY sounds like either the crystal itself, or maybe a cap or such in it's ckt. I also would get a voltage reading on the plate and grids of the burst tube--and any in the ckt. with the crystal--when you DO have color--and THEN again--after it goes away. You might find a big discrepancy, between the 2 conditions.

As for "trickle current" in this set--the answer is NO..this set did NOT have any sort of instant on ckty--so there should NOT be any current drawn by it--when switched off. If there IS--then SOMETHING is not right--such as a leaky line-isolation cap-- and MUST be looked into.
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Old 10-18-2014, 04:42 PM
DaveWM DaveWM is offline
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burst amp tube, color osc tube, band pass amp, check color killer setting.

If you turn the color down (while its working) is the green tint there (grey scale setting).
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Old 10-18-2014, 04:58 PM
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No. Good grey scale. When it looses color, barely there mostly green, like a tint with severe mute of color. Sometimes after the condition sets in, intermetent color pulses.
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Last edited by etype2; 10-18-2014 at 06:04 PM. Reason: Typo
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Old 10-18-2014, 05:57 PM
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When the 3.58 craps out on most tube RCA's it gives you a
pink & green pix. Not sure if this applies to the -15. Its distinctive
when you see it. Dont remember the layout but its best
to get at least one known good 6GH8 & sub it once at a time.
Do not move them around it will cause confusion. 'GH8's
will work fine in one place but not in another...... Lots of
folk would bring in all the tubes for testing & when they put
them back in had different symptoms.

Not this but also watch for a short jumper wire at the
demod tubes that carried the filament voltage. Very common.
Its brown & dries up badly.

73 Zeno
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Old 10-18-2014, 08:52 PM
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99.99% confident it's the 3.58 section. Saw a lot of them in the shop.
Phil
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Old 10-19-2014, 11:11 AM
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You all mentioned the 3.58 section. Thanks for the lead, will update later.
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Old 10-22-2014, 11:51 AM
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A few screen shots of the CTC-15 when working properly.



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Old 10-22-2014, 06:02 PM
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Could you post some shots of when it's not working properly. That might help verify it's condition.
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Old 10-23-2014, 09:00 AM
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I could do that. When the color go's about 3 hours after it's turned on, it looks like black and white with just a hint of color. When the scenes shift, I can see the color trying to come back a bit but very faded out. Best description I can come up with.
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Old 10-27-2014, 10:44 PM
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Sometimes the 3.58 osc. just needs a tweak one of my roundys would take ~1/2 hour to have it's color synch, work for a few hours then flake out again. Tweaking the osc. slug while messed up cured the issue.
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Old 10-28-2014, 09:05 AM
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That set sure produces a great color picture, when it's in sync, Yowza!! :-)
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Old 10-28-2014, 03:43 PM
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Let the set run for 3 hours...

until the color problem rears it's ugly head. Then perform a complete AFPC circuit alignment.

This will either fix the set, or reveal which circuit is malfunctioning.
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Old 10-28-2014, 03:48 PM
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always go for the easy fix 1st, wiggle tubes, esp the color osc.
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Old 10-28-2014, 04:32 PM
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Thanks guys.
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