[Collins] HP-23 PS With KWM-2A

[Laird Tom N]

>From the WC9M archives:

Hope this helps,
Tom Laird WC9M
Moline, IL.

----------------------------------------You have to add adjustable =
bias,
from the -130 supply,
add a voltage divider consisting of a 4.7K, 2W resistor,=20
a 5-10K pot, then another 4.7K, 2W resistor. take the
adjustable bias off the wiper, add a 20@250 cap to ground,
and that's it, if you need more or less, adjust the=20
"bottom" resistor (the one to ground) as necessary.

Then, you'll have to wire a cable from the PS-23 to the KWM-2.=20
Use the "12V" wiring as shown in the KWM-2 schematic. NOT 6v!

On the HP23B/KWM-2 I have, the low B+ (300v tap) runs 310 rx,
275 XMIT - even better than the 516f2. the High B+,
about 960, no load, 800 at 100W out.

Don't run extended digital modes on this combo, the PS will
run the KWM-2 forever in SSB, I limit my CW plate current
to about 180 ma, as I'm long winded.

I've found these units to be easier on the gear than the Collins=20
supplies, and more reliable than the (arc-prone)rectifier tubes.
-------------------more------------------------------------------

This circuit still works great. The KWM2A runs much cooler. JohnB K1JEB

I have built the circuit bellow and it works. I get 280Vdc in rcv
and 280Vdc in xmt. The nice thing about this circuit is that it's
automatic. There are no mods required in the KWM-2A. I got most of the=20
parts from Active Electronics in Wouburn, Ma. But any over the counter=20
components supplier may have these parts. Cost $14 and change. There
is plenty of room inside the HP-23 supply to add the circuit.

Parts needed:

3 100V 5Watt zeners (can use a 200V and a 100V or 150V and a 150V)
2 10Kohm =BD watt resistors
1 220ohm 10Watt resistor ( can use two 100ohm 10watt in series )
1 12Vdc SPDT relay (400ohm coil)
1 2n2222a transistor or any NPN 350mWatt with Hfe of 50 or greater

The 12V for the circuit can be constructed from the 12Volt filament.
You will need to build a power supply from 12Vac. See ARRL Handbook.
( I have converted the 12.6Vac (actually 14.8Vac) from the HP-23 to
12.6Vdc But, this is another project. I have no HUM from my KWM-2A.

John K1JEB
---------------
Regulating the HP-23 power supply 300V line

I hope that some one has found a way to tame the HP-23 power supply.
In receive the output supply is +310Vdc and in transmit it's +280Vdc.
The KWM-2A needs +275Vdc. I have a PM-2 supply which does the same
thing. Using a Ammeter my KWM-2A draws 172mA on receive and 250mA=20
on transmit. I like the HP-23 better because it fits nicely on a desk.

I'm thinking of circuits that will better regulate the supply.
One method is to use three 100V 5Watt zeners in series.=20
When the M2 is in receive mode there will be 310 Vdc supplied so=20
the zeners will be zenering with 10V across a resistor (to limit=20
the zener current) on the ground side.
The 10V will trigger a relay that will open and allow a 200ohm=20
10Watt resistor to absorb 35Vdc to bring the 310Vdc to 275Vdc.=20
When the M2 is in transmit the supply will only provide 280Vdc=20
and the zener diodes will be non-conducting and therefore no=20
voltage will be across the resistor. This will release the relay=20
closing the it's (normally closed) contacts bypassing the 200ohm=20
resistor. Allowing for 280Vdc.
The relay will be driven by a transistor sensing the voltage=20
across the resistor on the ground side of the zeners.

 +310Vdc ---------------------200ohm-------------------+275
               |            |    K1    |
              100V zener    ---o--->o---  [xmt) closed
               |                          [rcv] open
              100V zener            12V
               |                     |
              100V zener            K1coil (400ohm)
               |                     |c
              10Kohm----10Kohm----b-Q1 2n2222a
               |                     |e
              GND                   GND

Would like to see how other HP-23 supply users solved the problem. John
KA4DGF
-------------------------more-------------------------------------------=
----
-

I got it going, however I still have a problem, even though the =
voltages
look OK,
I do not get the same output as with the PM-2. These are the voltages =
that I
get at=20
key down 270+ low voltage 860+ plate -40 to -120 bias 6.3 vac. any
suggestions?=20
-----------------------

Be sure to check the filament voltage Hiram. When I have service these =
sets,
I noticed that the KWM-2 is prone to low RF output if the filament =
voltage
is not up to snuff, so measure it at the 6146 sockets. If low, check =
the
interconnecting cables and separable connectors, and then see what the
voltage is at the HP23.