[1000mp] 1000MP Power Supplies

[Harold Mandel]

After reading somewhere about possible switching
noise (hash) generated by the FP-29 power supply
it was decided to look further into the situation.

Firstly, dealing with switching supplies in my 
workplace it is found that switching supplies
have a much lower MTBF than linear supplies, and
that we replace three times more switchers than
linears in the telephone central office.

Secondly, the issue of hash and bypassing of the FP-29
caused me to listen to the radio and FP-29 running
with another HF radio not connected to the system,
but running on a battery. With no other appliances
running there were some "birdies" in the 3 MHz
band that were apparent and some stuff around
18MHz that were audible as well.

So I decided to invest in a couple of Astron linear
supplies, an RS-70M and an LS-25A.

Before ever connecting these some e-mails were 
read where Astrons catch fire on the circuit board
attaching to the one computer-grade filter cap used
in the supplies. Both the LS and RS use only one
capacitor, but these are different voltage ratings.

The LS supply does not come with a fan. The RS
does, and it works when a thermostat mounted on
the right side heatsink closes. This is easily bypassed
with a front panel switch. Both supplies grow warm
when touching the top steel covers after an hour of
operation. 

A fan from Radio Shack was added to the LS supply
with an afternoon's work on the kitchen table. The fan
attaches to the rear apron, mounted outside, and there
is ample room to do so. The power is derived from
the front panel power switch, with no thermostat.

The LS is able to be adjusted beyond 30.00 volts. 
By attaching a 250 watt, 6 ohm resistor across the
output the voltage sag observed is less than 1/2 volt
under load from no load. The output was set at 30.00
volts for the '1000MP.

Replacement capacitors are on the way for both these units. The 
LS uses a 55 volt, 35,000uF cap. This will be replaced with
two units of 35,000uF at 80 WVDC. Four of these caps
were purchased, and the other two will replace the 
35,000uF/50 volt cap in the RS unit.

A Molex-type plug and/or socket was desired for hooking
up the radio to the supply, with a jumpered arrangement 
from the other supply. No part could be found from Yaesu
parts department. That Molex connector is not available
at all. Another power cord was ordered so as not to destroy
the OEM power cord for the FP-29. This was stripped and
converted into ring terminal ends to fit the Astrons.

When completed and turned up & tested, the same jig was 
used with another radio listening. 

Regrettably, the same "birdies" were heard. I cannot report to you
any reduction in noise by going through this exercise.

The noises heard on the '1000MP stayed the same. However, here
in the "portable" location the RF environment is replete with all sorts
of signals as this is near many other appliances such as computers and
television sets, etc. It would take days to write down all the spurious
noises heard on the HF bands. However, the "biggies" were all still there.

Respectfully,

  Hal Mandel, W4HBM