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CONVERTING THE COLLINS 516F-2 POWER SUPPLY TO SOLID-STATE
These instructions describe how to convert the Collins 516F-2 power supply to solid-state using parts supplied in
the conversion kit from Harbach Electronics, LLC. The main advantages of the conversion are the removal of heat
from the 516F-2 and to prevent tube arc-over. The 516F-2's black power transformer absorbs quite a bit of heat
from the rectifier tubes. Extending the life of this transformer is well worth the effort.
Collins engineers recommended solid-state conversion in SIL 1-76 (available on the CCA website –
). While this is not an official service bulletin, it does show their concern with tube arc-
over. It is generally believed that Collins had a solid-state version of the 516F-2 in development, but was never
released.
Another advantage is the reduction in filament current by removing the two rectifier tubes.
There has been quite a bit of controversy on modifying the 516F-2. Some believe that the conversion will allow B+
on the plates before the filaments are sufficiently warm. The rectifier tubes in the 516F-2 come to life (produce plate
voltage) well before the tubes in the KWM-2 reach operating temperature. In addition, the 6146’s are biased to
cutoff at power-up, so no electron emission will take place until the PTT line is closed. There have also been many
KWM-2 transceivers powered by a Heathkit HP-23 solid-state supply for years. In any case, thousands of owners
have converted their 516F-2 with great success.
There are several recommendations to perform this conversion in addition to replacing the two rectifier tubes with
some solid state equivalent. First, there is a transient suppressor that should be placed across the AC line input.
Next, there is a 25-watt resistor to reduce the increased output voltage caused by the conversion. Then, there is a
solid-state diode replacement for the selenium diode used in the bias supply circuit. Finally, there are two diodes
connected back-to-back to eliminate the power-on slamming of the S-meter.
Read these instructions very carefully. Now unplug the power supply from the AC outlet and from the radio. Place
the supply on the bench and remove the power supply chassis from the outer cabinet. You are now ready to
proceed with the installation.
Be sure to let the power supply voltages bleed off before beginning the conversion!!!
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Verify that you have all of the parts shown in the following parts list.
PARTS LIST
QUANTITY PART
2 5U4/5R4
SOLID-STATE TUBE REPLACEMENTS
1 200
Ω
25-WATT ALUMINUM-HOUSED RESISTOR
1
METAL OXIDE VARISTOR (V20E250P OR EQUIVALENT)
1
1 KV @ 3A DIODE (1N5408 OR EQUIVALENT)
2
1 KV @ 1A DIODE (1N4007 OR EQUIVALENT)
1
12” #20 STRANDED BLACK WIRE