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#1
06-30-2015, 08:18 AM
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ZENITH 26kc20 QUESTION
Need advice. Red gun only appears to be out of focus. When trying to converge my red gun on both crosshatch and dots only the red gun is bigger and thicker and overlaps top and botton of Horz lines and when using dots the red is a bigger less focused blotchy dot that surrounds the converged blue and green. My crt tests good and also I had another good crt in the set and has same problem. The color tracking is fine and when watching color show it's hard to tell. B/W look like red is badly out of convergence and Salt and pepper snow is pink. I need some direction cause I don't think this is a problem with the convergence but something wrong with the red drive. If I lower the contrast the red on the dot patterns becomes more focused. Please help.
Perry 
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#2
06-30-2015, 08:42 AM
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Have you checked the picture tube?
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#4
06-30-2015, 11:14 AM
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Quote:
I have an RCA CTC 12 with this same issue and the 21FJP22 CRT cutoff tests great for green (of course  ), marginal for blue but red is far behind both. I have a B&K 467 with three meters, so you see the cutoff variations in comaprison. The emission alone seems OK on all three but when you compare separate rasters, not so much.
__________________
"When resistors increase in value, they're worthless" -Dave G
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#5
06-30-2015, 11:44 AM
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My 25mc33 had a similar problem. I used a Beltron and it brought the tube back up.
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#6
06-30-2015, 02:57 PM
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Sorry, I see your post that you tested the tube. What kind of tester did you use.
If I remember right, the red drive is set at full and the green and blue are brought up to match it from minimum. Are the screen controls adjusted properly? Both of my sets are fairly critical on focus and start losing it if set too high. If possible, also check your high voltage. Usually, if the 6BK4 goes bad it goes way too high. I have seen chassis trouble make the 6BK4 pull down the high voltage. If the voltage is too low focus suffers first then width.
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#7
06-30-2015, 03:20 PM
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After seeing that you had tested the tube, I also was wondering about any of the
grid voltages other than G1 and Cathode of course.... Gotta be something unique to the red, or you would have it in other colors..... .
__________________
Yes you can call me "Squirrel boy"
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#8
06-30-2015, 04:12 PM
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Except for screens, cathodes and G1s, I think all the rest are in parallel with each other. I have to look when I get home at the schematic. Nearly sure.
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#9
06-30-2015, 08:24 PM
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Thanks everyone for helping me with this 26kc20. It seems that although my Silvertone Hi-lite crt shows good emission on BK470 the gun has less raster then the others. I did clean and balance and adj HV to 25K. Was at 23K. There's a noticeable improvement but I still wish I could get slightly more contrast without the red losing focus.
Thank you, Perry
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