[Amps] L4B biasing

[Jim Thomson]

Date: Wed, 24 Dec 2014 13:23:12 -0800
From: Paul Baldock <paul at paulbaldock.com>
To: mikflathead at aol.com,amps at contesting.com
Subject: Re: [Amps] L4B biasing

Yes you should add bias. I added 11 diodes in the center tap of the 
filament trany. So that would be about 7 volts.

- Paul

## One other quick note.  With the oem +130v  cut off bias scheme, the center contacts
on the TR relay will eventually fry.   With the contacts in mid air, the cathode will try and assume 
full B+ voltage.  You cant open off the B- on a GG amp at any time. 
With the 50-100K resistor in the CT of the fil xfmr, you never have that problem.
The center contacts of the TR relay are simply re-wired so that the 50-100K resistor is shorted out
on TX.  If the oem 3PDT   TR relay is being used, the oem half wave rectifier can be swapped to either 
a FWB or a FWD.  If swapped to a FWD, you end up with +67 vdc, instead of + 28 vdc.  
The tr relay will operate a little faster, but not fast enough for qsk.  + 67 vdc will speed up a 
26 vdc vac relay nicely.   +28 vdc will speed up a 12 vdc vac relay just fine.  Gigavac makes the
popular GH-1 vac relay in either 12 vdc  or  26 vdc.  A 50 uf cap across the series drop resistor 
will speed up any relay  even quicker.  Called a RC hot shot circuit. 

later.... Jim   VE7RF