[Boatanchors] B&W 5100 xmtr

[manualman@juno.com]

Gary:

Your correct. When the meter switch is in the grid position, the meter is
reading the power amplifier screen current. There is no way to read
actual 6146 grid current from the front panel meter in its present
configuration. There was also a number of service bulletins on the 5100
including one that provided buffer mods and a complete bias modification
so that the final amp is cut off when the key is up. Also provided
procedures to add variable bias potentiometers for both final amp. and
modulator tubes. For the other fellows question, the modulator resting
current and the CW resting current is 55 MA. From the 5100B manual, with
transmitter fully loaded and HV applied, modulator resting current  may
drop to around 40 MA during normal phone operation.

As you also indicated 6 MA on the grids of the 6146's should be maximum.
17 MA would make them real perky for a very short time. If you wanted to
read actual grid current, one way would be to break the lead going to
terminal 4 on P5 of multiplier-final amp. module and install a current
meter in series with the lead.

Pete, WA2CWA


On Sun, 3 Aug 2003 20:28:06 -0700 (PDT) Glen Zook <gzook@yahoo.com>
writes:
> Looking at the B&W 5100B manual the readings are not
> for the grid current of the 6146s, but is for the
> screen current!  I wonder if that is what they mean in
> the B&W 5100?  The screen current is to be between 20
> and 22 mA in the 5100B and around 17 mA in the 5100. 
> That makes more sense.
> 
> But, it has been a year, or more, since I have even
> seen either version so I don't remember if there is a
> way to actually measure the true grid current.
> 
> The grid current on a pair of 6146 tubes definitely
> needs to be kept below 6 mA!
> 
> Glen, K9STH
> 
> =====
> Glen, K9STH

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