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Author Topic: B&W 5100 lack of control grid current metering?  (Read 93 times)

W1BR

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B&W 5100 lack of control grid current metering?
« on: September 19, 2020, 09:11:22 AM »

The transmitter uses a pair of parallel 6146 tubes in the PA,  driven by 6AQ5 multiplier stages.  The only metering provided is for screen and plate current.  Why wasn't G1 current a concern, especially in a AM transmitter designed for old buzzard locked down AM diatribes?  Does the G1 current closely follow G2 current when tuning?

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KM1H

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Re: B&W 5100 lack of control grid current metering?
« Reply #1 on: September 20, 2020, 11:24:01 AM »

With a 6AQ5 driver I doubt Ig will get much beyond the RCA 1952 4 ma spec per tube was an issue, it wasnt until years later the DX-100, Viking II, and other owners with grid current metering found short 6146 life at those levels. B&W was off in another world I guess and "assumed" the "Tune" procedure/position for Phone would limit HV and screen current to low values and G1 would just follow along!

I didnt keep my 5100B long enough to take out the finals.

Carl
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