Some time ago I posted a message regarding broken filament connections
in a pair of 3-500Z, and asked the proper method for resoldering their
pins. I got the AG/Sn solder and resoldered them with care, they're
working fine now. But, the internal fan, although it runs, is
overheating. My first question is, maybe this overheating is due to our
50 Hz line frequency?, anyway, the amp has been running many years as it
was with the same fan, we noted this now. I measured line current at 110
VAC and it takes nearly 1,5 Amps. A lot.
The last question is about final tuning settings; the owner use it
always at CW plate voltage (1800 VDC with no load, 1600V at 500 watts
out), he don't want to "pull" it at 2500 VDC (SSB mode). The user's
manual state to run grid current from 200 upto 400 mA. We found tuning
conditions with above stated power output, 500 mA plate current and grid
current of 200 mA, in the lower limit.
Could a lower Ig (maybe 100...150 mA, with less drive, taking in care
all other tuning settings are well adjusted) make any harm to the
tubes?, or the manual recommendations are regarding best possible
linearity and/or efficiency?.
Thanks for past advices.
Best regards
Guillermo - LU8EYW.
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