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It seems that the problems of horizontal output are not my problems alone. Thank you for your comment and the scanned page, which helped me to understand how the sawtooth-waveform is generated in the horizontal oscillator. This gave me the kick to check the older RCA chassis too. And what did I found? ctc4 and ct-100 had both a horizontal drive control. The remaining circuits are nearly identical. The 6CB7 have the same kathode grid voltage difference, appr. 50v. But in the ctc-4 there is an extra -29v source in the power supply only for the 6CB5. No grid voltage of the 6CB5 was used for brightness control level like in ctc-5 and no d.c. connection to the grid of the horizontal oscillator. Between c154 (ctc-4) and the grid is only one R160 with 470K to kathode. The ctc-5 seems more puzzling here.
It is interesting to know whether the ctc-4s had the same trouble with high horizontal output currents and low drive voltage at the grid of the 6CB7. Does somebody here has some experiences with the ctc-4? Can somebody here provide the schematics for the ctc-7 or ctc-9?
I have added a 0.047 cap again to c609. At kathode of 6CG7 still I read 12v. But there is very low high voltage but very high focus voltage (it's arcing). With 0.0047 the set is running "properly". Another point: c611 is critical. instead of 82 it was replaced with 100. I have replaced it with 82, and horizontal current increased a little.
The schematics of the ctc-5 are much more interconnected with other units in the set than the former models. One possibility is to insert a drive control like in the ctc-4.
The other possibility is to renew c609 with 0.047 and do a complete re-adjusting of the horizontal oscillator and output unit. On page 17 of the service manual is a method how to adjust horizontal output correctly. I have an old oscilloscope from the 1960's on the attic, which I will arouse again to life for that.
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02-18-2005, 03:24 PM
Hybrid Mode
