On Thu, 28 Aug 97 08:07:34 -0800 Rich Measures <measures@vc.net> writes:
>>Next, power up with both tubes removed...making sure there are no
>>fireworks, etc.
>>
>>Install one tube at a time, looking for unwanted plate or grid
>current.
>>If all is OK, close the relay line and look for some idle current;
>about
>>50ma in CW position.
>
>The filaments are in series in a TL-922.
I'm glad you caught my goof Rich. I went from 922 specific to generic
thinking there.
The mind is the 2nd thing that goes...
Tnx and 73....Carl KM1H
The above test puts 14a
>through
>the cathode CT DC return choke - which is obviously designed to carry
>a
>lesser amount of current, so tarry not.
>- Another reason not to tarry is that the 922 uses voltage cutoff
>bias,
>so if a tube has a grid to filament short, a short is automatically
>placed on the 110VDC cutoff bias supply, which will destroy its
>unfused
>transformer in short order. If the 922 is converted from
>voltage-cutoff
>bias to resistor-cutoff bias, the transformer can not be
>crispy-crittered
>by a shorted 3-500z. ........ SB-220s suffer from the same design
>weakness.
>
>N.B.: There is apparently no such thing as a perfect amplifier, so it
>
>might not be a really great idea to toss out your soldering iron.
>
>Rich---
>
>R. L. Measures, 805-386-3734, AG6K
>
>
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