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#2
11-27-2006, 08:28 PM
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I would suspect 13v would be low. At the junction of r503, r504 it should be 50v p-p. It should be a negative pulse. You may have a low output from the sync seperator stage. I would check the voltages on the 6ka8 tube. Along with the usual caps I notice there are a couple of high value resistors in the seperator circuit I would double check. I would check the tube itself also.
Good luck Bill R 
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#4
11-28-2006, 10:56 PM
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With the correct signal at point 6, the sync seperator is ok. I thought that was what you were looking at. Now I understand. Is the hold control centered. This would indicate the oscillator is on or close to the correct frequency. Sounds like you are. I looked back at your previous thread about the size problems. Is there a setting of the lin control that produces a stable lock? I have seen the setting of the height and lin controls affect the stability of the sync. Looks like feedback for hold is off the cathode of the output tube through c507 (you did replace that one right?) the hold control and a resistor to the grid of the oscillator. Feedback from the plate of the output to the grid of the osc tube only has a few caps I would replace them regardless of how the check. I checked Sams and RCA schematics and both call for about 100volts on pin 1 of the 6ka8, so the 97v you measure should be close enough.
For servicing the chassis, I use a color test jig. I have a sylvania ck3000 test jig. They show up ocassaionally on ebay and are extremely useful by allowing you to put the chassis on the bench out of the cabinet for service. There are several manufacturers of these, they are basically a crt in a case with the appropriate loads for convergence and the deflection adaptors. Mine even has a hv meter inline so you can monitor the high voltage. Bill R.
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#7
11-30-2006, 08:24 PM
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Sounds like there is still a height problem. I have been looking at both rca, and Sams schematics, and there seems to be some discrepency. Surprise! On the RCA schematic 50 volts on pin 1 or the 6em7 is normal. On the Sams schematic it shows 30 volts on pin 1. Plate voltage on pin 2 shows 360 volts on the RCA schematic as normal, that sounds right since it is fed from the 405 volt source through the primary of the vert trans. Sams shows a .22 cap off the wiper of the vert height control, and not on the lin control, but RCA shows the cap on the vert lin control. RCA also doesn't show the service switch so I assume some models may not have had one. Sams does show the service switch. On the RCA schematic it shows the height control conected to the 270volt source, and the lin control conected to b boost voltage. On the Sams it is the opposite, height to boost and lin to 255 volt source. On the RCA CTC 11 schematic it agrees with Sams. Height and Lin seem to be mislabeled on the 12 schematic. My RCA schematic is from the field service guide and matches the one you posted. Sams is 640-3.
I think I would set the controls for best sync and relook at the height problem. My scanner and computer are no longer on speaking terms, maybe someone could scan the Sams schematic for you. Bill R
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#9
12-01-2006, 08:19 PM
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Well I guess working out the schematic puzzle is part of the fun.
Those voltages look right on (or close enough) so whatever is causing the insufficient height by upseting the output stage bias is causing the bad sync. These problems were always fun. I think you may be right on with the flaky resistor. Bill R
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#11
12-02-2006, 11:26 AM
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Great job!
I would check all the solder connections where the board solders to the chassis also. In fact I usually would do this to all the boards since bad grounds can cause all kinds of strange intermittent problems. Bill R
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#13
12-08-2006, 01:43 PM
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Now that we have all helped you
can we see a photo?
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#14
12-08-2006, 01:45 PM
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DId the switch clean up?
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Linear Mode
