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Old 31st Dec 2011, 3:20 pm   #4
Anthony
Hexode
 
Join Date: Sep 2006
Location: Hertford, Herts. UK.
Posts: 338
Default Re: Cossor CDU110 'Scope: Brightness Probs.

When I said 'Brightness', I meant I do not understand how the 'Beam Current' control works. Apologies.

Following Peter's helpful suggestion have checked all rail voltages and EHT - all good. Also the Grid voltage seems to vary sensibly with the Brightness Control, going from -1126 to -849V. The trace appears at about -999V but further decrease of the negaive voltage makes little difference. That does not seem right?

Have recapped C64 and C65 to no effect. The 'Beam Current' setting measured across R50 is still out of spec. I cannot get it above 0.35V whereas the manual shows 0.45-0.65V.

Could it be the tube itself?

Any suggestions again gratefully received. Thank you.
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