Re: {Collins} Collins S-Line power supply questions revisited.

Fred :  thank you for your report, some months ago i had asked about a bias
voltage issue and Peter K2LRC responded and was a wealth of information and
support and now finally seeing your test results, i decided to finally see
if i could find my own problems and sort them out. I have 3 supplies each
one was modified by K7RMT and include the much needed AC relay wherein it
takes all the load burden off or away from the Oak switch and makes the
relay carry the switching load inrush of current.  But back to your results
and mine as i followed your testing pattern.

My results were close to yours until i actually keyed the rig under test,
in this instance i used a KWM-2A albeit an old one from 1965 .  When keyed
the High B+ and the Low B+ did show some sag that actually brought the
voltages into acceptable or expected tolerances. The BUDster was really
pretty smart on his effort, that if you want,  one simple jumper between
the 25 watt 250 ohm resistor and installing TUBES in place of the Solid
State rectifiers and wham your supply is fully stock.

The Hi B+ was typically right at 1000 vdc and in no instance of my 3 supply
test did the Hi B+ sag more than 60 volts from non KEYED to being Keyed,
the Lo B+ in no instance sagged more than 10 volts when keyed.

Each supply had a input Bias from -160/-155/ and finally -162  2 of the
bias pots were of the older value at 2500 ohm  and 1 was the newer model at
5000 ohm . going through the Bias ckt it produced bias voltages  from -58
to -115 and my best unit produced -49 to -71vdc .

 My KWM-2A to be set for 50ma likes to see an actual voltage of -56 vdc and
that would yield 50ma for the desired idle current reading if you plan to
use a linear amp in the output stream, otherwise the manual recommends 40ma
as the idle current when the rig is keyed. So really i had only one supply
that would meet my 50ma needs, it looks like the other 2 will require some
resistor changing to see a lower bias voltage that will result in reading
of 40 or 50 ma for idle current readings and set up for linear amp

One interesting note i observed was a significant S-meter ZERO or resting
setting point, strictly dependant on the bias setting.  So clearly there is
also some interaction of bias and the S-meter able to rest at ZERO when not

It would be very unfair if i did not include that after Peter offered so
much help on my Bias issue,  I felt very comfortable to send him my KWM-2A
for service, I simply could not be more pleased, he work is quick, very
professional, his turnaround time is great, the set works as new in every
respect, I contacted several of the other popular names offered about,  but
really when you talk a bit in detail and ask questions,  Peter was very
comfortable and walked me thru each of my concerns, my old set has the
telephone relays and the set could simply not work a bit better.

regards: JG

On Thu, Dec 20, 2012 at 9:40 PM, <wa7uhr@xxxxxxxxxxx> wrote:

> Boys and Girls,
> A while ago I posted with some questions about the 516F-2 power supply
> voltages with the power supply unloaded.  The DC voltages seemed to be
> about 20% higher than the specification on the schematic.
> I did find a problem with one of the two supplies tested and that was a
> faulty bleeder resistor (burned open) in the High Voltage circuit.
> Repaired and with the stock capaciators fully tested as okay in WE and RE
>  units I came up with the following unloaded voltages for the 516F-2s' and
> also a late model PM-2.  So, here ya' are.
> Using a variac and a Fluke 77 DVM to measure the DC power supply voltages
> here's what I came up with for each supply tested:
> WE 516F-2                                           RE
> 516F-2                                   PM-2 (late model)
> AC input 93vac                                        AC input
> 90vac                             AC input 93vac
> HV = 8oo vdc, 7vac ripple                       HV = 800 vdc,    5vac
> ripple               HV = 800 vdc, 1.5vac ripple
> B+  = 325vdc, 325 .1vac ripple               B+ = 328vdc, 1.2vac
> ripple           B+ = 294vdc, nearly 0 vac ripple
> Bias -44 to -80vdc on the pot                  -48 to -88vdc on the
> pot               -39 to -52vdc on the pot
> -----                                                  -----
> -----
> AC input 120vac                                   AC input
> 120vac                             AC input 120vac
> HV = 1081 vdc, 11vac ripple                 HV = 1095 vdc, 8vac
> ripple           HV = 1057 vdc, 3vac ripple
> B+ =  410 vdc, .1 vac ripple                  B+ = 427 vdc, 1vac
> ripple             B+ = 364 vdc, nearly 0 vac ripple
> Bias -57 to -108vdc on the pot              Bias -63 to -104vdc on the
> pot      Bias -52 to -108vdc on the pot
> So, in each case the power supply readings  were within a few percent of
> eachother unloaded and not plugged into a KWM2-A or a 32S type
> transmitter.  Tests are for information only.  I believe each of the power
> supplies tested would work okay in any Collins S-line transmitter or
> transceiver.  I am gonna' try the Round Emblem out on my KWM2-A and
> probably keep the PM-2 as a spare as it was the one that has been  working
> with my M-2.
> The other WE 516F-2 in a cabinet will go up for sale later on.
>  By the way, thanks for all the input I got from everyone regarding
> "Higher than schmatically" (normal) DC voltage levels in the S-line
> equipment power supplies.
> Fred.
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