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Old 3rd Jan 2012, 2:01 pm   #12
Brian R Pateman
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Join Date: Jun 2005
Location: Western Lake District, Cumbria (CA20) - UK
Posts: 2,136
Default Re: Cossor CDU110 'Scope: Brightness Probs.

The power stages for 'scopes don't bear much resemblance to those found in television practice as a rule.

Refering to the circuit which Bill has provided in post number 5 this one is no exception. The heater voltage will be derived from a transformer winding (I can't recall if it's AC or DC) and should be easy to measure. Scope tubes are very forgiving of lower than ideal heater voltages and in over 30 years of working with them I've found very few low emission 'scope tubes.

That said a quick check of R72 which ties one side of the heater to the cathode might be a good idea if you haven't already done so (I'm at work so don't have time to read back through all the posts).
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