[Amps] MFJ products

[donroden at hiwaay.net]

Many years ago I dismantled several old broadcast transmitters, and I  
built a bench supply out of two 7 volt 180 amp filament transformers
( tubes with handles ).   Another similar transformer served as a choke input.
It had about 1/2 volts ripple at 18 volts out.  I built a regulated  
pass transistor to a one ohm resistive load as a way to test the  
supply under load.

I found that I could set the pass transistors  10 2n3055s to just at  
the middle of the 1/2 volt ripple and the pre-regulator voltage ripple  
could almost be eliminated.  If I recall correctly, the load  
dissipated around 50-100 watts.

   Re-tapping the primaries of the two transformers to 260vac gave  
around 15 volts, which I ran to the back of the radio desk for the  
Icom, Kenwood, and Yaesu radios.

I thought about using a 250vac variac on the primaries, but none of my  
radios or projects ever caused the supply to drop below 13 volts, and  
all of the radios were comfortable at 15 volts.

Don W4DNR


ps......  if you are "really" concerned about a pass transistor  
shorting out, put a marine storage battery between your supply and  
your radios.
( Proper fuses of course )

The battery becomes a "MEGA-capacitor" and eliminates surges/brownouts/spikes
from damaging your $5000 toys.