[Boatanchors] Multi Elmac Power supply questions.

[Philip Atchley]

Hi,
I was talking to my friend today about the Elmac AF-67 he has along with a
power supply.  I'm considering trying to put this rig on the air and have
already had some of my questions answered here.

Power supply:  He has a Heathkit HP-23A supply that he said I'm free to modify
as needed to get the Elmac on the air (even has the plugs for both TX and PS).
Here are some questions I have.

The Elmac manual says the AF-67 wants to see about 500 Volts (max) for the
6146 and modulators and around 250 Volts for the low Voltage along with either
6 or 12 Volts for the filaments.

The PS-23A puts out 800 Volts open circuit and about 700 Volts with a 250MA
load.  I anticipate it'd probably be around 750 Volts with the 100Ma load from
the Elmac, WAY too much for it!

Now, I have several options.  I don't think Number 1 is a real option as I
think regulation would be WAY too poor for acceptable performance, with the
Voltage swinging back up to 800 Volts under "key-up" conditions.

1.  Use the PS-23A primarily "as is" with a dropping resistor to drop the 800
Volts down to 500 Volts under load.  Advantages, I can use the low Voltage
250 Volt tap and filament Voltage from the PS-23A with no modifications of the
supply. BIG disadvantage, regulation as mentioned above.

2.  Modify the PS-23A so that the Voltage Doubler in the 800 Volt supply is a
regular Bridge rectifier and be satisfied with about 400 Volts on the 6146
plate under "Key Up" swinging down to perhaps 375 Volts (my guess factor)
under load.  Under these conditions everything would run nice and cool and
would probably do very well for CW, AM "might" be sucky! HOW WELL do 6146's
work with 375-400 Volts on the plate?  Maybe 25 Watts CW?

3.  Use the PS-23A "AS IS" with a Variac to drop the plate Voltage to 500,
which would also drop the low Voltage (I could use the 300 Volt tap) as well
as the filament Voltage being too low to use.  This would REQUIRE a separate
filament transformer to run the Elmac.  DISADVANTAGE:  Need to tie up a
borrowed Variac full time, if you "forget" the Elmac gets Zapped with 800
Volts!

4.  Try to locate an Elmac PS-2V power supply in ANY condition and re-cap,
overhaul as needed.  While this is the "nicest" idea, it's probably not too
practical with a "flat" wallet.


73 de Phil KO6BB
REAL Radios "Glow In The Dark".

RX 1:  Hallicrafters SX-71 (circa 1955).
RX 2:  Grundig YB-300 digital (doesn't glow, spotting set ONLY).
Antennas: 65' sloper, 1/2 size G5RV Inverted Vee,
                 15M Inverted Vee, Hustler 6BTV Vertical.