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  #1  
Old 02-05-2012, 09:00 PM
DaveWM DaveWM is offline
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Ctc-9

well looking good but for some oddness focus (need the focus voltage is about 4kv and it need to go lower which seems odd as that is the direction needed).

HV will bloom out if color is turned up much, and color is way too strong. I think there is a problem here so will need to check the CRT pins for bias.

If I advance color beyond 1/2 it goes all peter max on me and will bloom, HV goes away. Will have to study this a bit.
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Old 02-05-2012, 09:07 PM
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wow, checking the sams show the HV should be no more than 21kv and focus around 3-3.5. Seem I need to look a bit harder around there.
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Old 02-05-2012, 09:11 PM
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hmm those 3 22meg resistors show as 5% on the sams, I did not see any gold bands on them in the circuit. there are some other resistors in there as well. But before I go off on all that I will adj the HV down to 20kv and see how it all looks.
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Old 02-05-2012, 10:21 PM
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just fooling around with it I found that if I put a 22meg resistor between the focus pin and ground, the focus comes in nicely (at about 3.5kv) I did not check the screen voltages on the CRT, I assume the focus is done by some electrostatic deflection between the focus screen and the G2, but not sure about that. This set uses a pot that goes between two leads off the fly, maybe on side of the pot is open (low side of fly take off lead). well at least I know the CRT can focus, just need to work on the voltage.
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Old 02-05-2012, 11:13 PM
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went back a read sams, says setup HV for 23.5 so did that and focus is better, but still a the extreme end.
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Old 02-05-2012, 11:42 PM
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I have the same issue with mine(CTC-9A). I have not really tried to fix it yet. Focus all the way to one end. It's watchable but could be better.
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Old 02-06-2012, 08:43 AM
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do you recall if its fully CCW (lowest focus voltage)?
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Old 02-06-2012, 11:00 AM
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Yes I believe so. I think its around 4500V. Should be lower
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Old 02-06-2012, 11:49 AM
DaveWM DaveWM is offline
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yea that's the same as mine. I hope to check it out later tonight. there is a 27k resistor that is part of a voltage divider that the focus pot connects to. I dont recall checking that as I would have had to take it out of the circuit.
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  #10  
Old 02-06-2012, 02:15 PM
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put it on the vectorscope, it has the standard cross hatch pattern. the vert lines have jagged edges all the way down. a few in each box. I tried another signal generator and go the same thing. Also I get the poor vert lines on the very top (hooked). It does not seem to be an issue when receiving reg programming from a DVD or conv box.
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  #11  
Old 02-06-2012, 08:28 PM
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while I had it out on the bench I noted a hard to see film cap on the grid of the color killer tube to ground. a nice dipped cap, it was pretty small and had a value of .047 so I figured it prob was one of the 200v series that have tested so bad. I removed in a sure enough it was shorted at 150v. Replace with a 630v dipped cap. I have now replaced or checked every single film cap. Watch out for those 200v dipped....
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  #12  
Old 02-07-2012, 01:02 AM
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Film caps-are those the "maroon drops" or similar ones, that were thought to be mostly OK until the last couple of years? My CTC-7 (a future project) looked like it is full of those.
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Old 02-07-2012, 05:34 AM
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Must be a late production 7, mine was all paper caps.
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  #14  
Old 02-07-2012, 08:21 AM
DaveWM DaveWM is offline
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well the focus pot is fine, the 27k pot in series with the pot is fine, I did P up another resistor to one of the 22megs in the focus load resistor string to get it right at 66meg.

I need to find the jumper on the shunt tube and check it out as well.
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  #15  
Old 02-07-2012, 11:29 AM
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Phil Nelson Phil Nelson is offline
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Quote:
Originally Posted by ChrisW6ATV View Post
Film caps-are those the "maroon drops" or similar ones, that were thought to be mostly OK until the last couple of years? My CTC-7 (a future project) looked like it is full of those.
Mine had nearly all maroon drops (dipped, like orange drops), except for a few oddballs that might have been replacements.

Maybe I was the only dope who assumed they would all be good. Anyhow, in my CTC-7 article is a series of screen shots showing how the picture improved by stages -- from horrible to watchable -- as more and more of them were replaced.

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