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Old 01-24-2017, 08:33 PM
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Penthode Penthode is offline
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Join Date: Jun 2009
Location: Kitchener/Waterloo Ontario Canada
Posts: 1,059
Have you checked the tubes on a transconductance checker? My set was relatively low hours yet I found a number of the tubes weak in the signal path and needing replacement. The good thing is that most of the replacement tubes are cheap on ebay.

The biggest drawback of the CTC5 in my opinion is the low high voltage coupled with the relatively dim (compared to tubes a few years later) 21AXP22A.

The low high voltage appears to be due to an inherently bad design. My set barely makes the design regulated 19kV: it would dip below the regulated output when the brightness was advanced. An immediate help for this was to substitute a solid state 3A3 HV rectifier so it at least now maintains regualtion at 19kV. If I get the time, I would like to explore further the Horizontal Output/ Flyback to see if I can a bit more HV.

The 21AXP22A in my set is original and shows good emission and life. But the picture is just dim. I compare it with the CTC11: the CTC11 picture is bright and brilliant. No comparison.

I suggest that the earlier less efficient phosphors in the tube coupled with the low high voltage is an inherent problem with the CTC5. Perhaps I should express my gratitude for the dim picture on the CTC5 as it probably explains why my set survived until now.
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