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  #1  
Old 12-17-2013, 08:46 AM
DaveWM DaveWM is offline
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odd color prob CTC-12

this one is tough,

in some scenes a solid color (like a red apple) will shift hue with half the apple red, and then some purple. Sometimes a solid blue scene will be half blue half green. the split takes place such that the top half of the apple is red the bottom is purple, so its always a full scan line that is shifted. this makes me think its in the reactance control of the 3.58 osc. Maybe some thing besides the burst signal is getting thru?

I will have to get a pattern generator on it to see if I can duplilcate. Its not purity as it moves about the screen. And its not constant, I can watch whole shows with not issue.

It does seem worse on highly saturated primary colors found in comercials.

I think I can clear it by tweaking the horz hold (if I can catch it, hence the need for a pattern generator that I can do a solid color).

So it seems like the ref osc control is shifting. Its not hum as it does not seem to move.

Things I think it maybe:

flakey 6GH8 tube ref osc (random shorting)

burst amp tube/flyback pulse feed cap (burst amp not cut off at the right time). thinking this due to the horz hold adj seeming to fix. adj horz hold def effects the hue more than I think it should.

maybe a flakey cap feeding that pulse.

Main thing is I need to be able to get the problem to manifest and stay put long enough to check things out.

Last edited by DaveWM; 12-17-2013 at 09:52 AM.
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Old 12-17-2013, 09:59 AM
DaveWM DaveWM is offline
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starting with a sub of the Burst amp tube a 6EW6...

so far looking pretty good, although the tint range has shifted to the green (good face tone, but cant shift to the purple and green is too green on tint control).
A 1/4 turn of A17 (burst phase detector transformer) got the face tones centered and good tint range.

Update: after watching for over an hour did not see the problem again. will keep monitoring it, esp those high saturation commercials. I did test the 6EW6 that was replaced and it did have shorts on both pin 1 and 2 (confirmed to nos tube that had no shorts). The pin 1 was a very mild short the pin 2 was more solid.

Last edited by DaveWM; 12-17-2013 at 12:26 PM.
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  #3  
Old 12-17-2013, 01:01 PM
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old_tv_nut old_tv_nut is offline
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Sounds like you found it. A good source for this kind of sleuthing is a test pattern DVD with various images including full color fields.
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Old 12-17-2013, 01:12 PM
DaveWM DaveWM is offline
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I did not have the DVD player setup so if it acted up any more I was going to do just that.

Different problem, flyback heat, I plan to punch out a 1.5" hole right over the flyback and mount an external muffin fan. I just do not feel good about how hot the flyback gets.
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Old 12-18-2013, 12:18 PM
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miniman82 miniman82 is offline
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Horizontal setup procedures outline how to get cathode current in spec if it is out, but beyond that it's sometimes possible to get it under the stated current draw through enough tweaking.
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Old 12-18-2013, 02:31 PM
DaveWM DaveWM is offline
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done all the setup, 175-180ma everything looks right it just runs hotter than I like.
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