[MRCA] T-195 Power Supply Options

[D. Platt]

Mike Murray wrote:
> OK, guys, second question:
>
> As some of you know, I recently acquired a AN/GRC-46 with "everything except the shelter" (as Brown stated it) in VG condition.
> Ted and I took it for a test drive in Gilbert, and I have issues with the T-195. The R-392 is excellent, though, so I am happy already.
>
> Vic-K0OUX here in town and I are weighing options for a power supply to run the T-195 and begin our troubleshooting.
>
> We were wondering how others are running their T-195s and what options we have.
>
> We have a 28V 100A power supply and 5 huge caps - 75VDC 60,000uF. The PSU is switching, however, and we were hoping to limit the surge. Possible? Anybody know the time constant of the surge?
>
> What else can I do? 
>
> I know I need to replicate Ted's awesome supply!
>
> Thanks again guys!
> 73
> Mike
> KW4HF
> Chapel Hill, NC
>
>
>   
Having some limited experience with the issue(s) and with all three 
variants (that is, all dynamotor, HV solid-state/LV dynamotor, and all 
solid-state), that I had, might I offer my anecdotal information.   I 
measured the in-rush current of my all-dynamotor unit at 95 Amps (peak) 
for approx. 2.8 seconds.  The rise-decay time was measured for when the 
current dropped back below 50 amps.  The method used was via a 466 
storage scope and a 100A shunt.  I also found that the in-rush was less 
that 50A for the one with the solid-state (only) power supply.  The all 
solid-state unit ran an even 36 amps with no appreciable in-rush.  My 
impetus was to see what was necessary to run the units with a PP-4743A 
(GRC-106) power supply.  The all-dynamotor unit would _always_ pop the 
PP-4763A breaker.   Until modified, I used a commercial, 60 amp, 
ferro-resonant supply that would sag to about 18v during the inrush 
period and build as the in-rush decayed.  This supply was very 
tolerant*, obviously, and was used successfully with a PE-73C dynamotor 
with the BC-375.  My other setup had a Navy 40 amp supply and two sealed 
lead-acid batteries.  The system worked well butt he issue with them was 
that the T-195( ) likes to have something above 28v and that caused the 
batteries to be charged at higher than acceptable value (Rock and hard 
place...!).  That setup was relegated to the BC-375 for a while as 24-26 
volts was OK.  Just before I divested the GRC-19's, here, I did build up 
an in-rush box consisting of a 1000w, 0.2 ohm wire-wound resistor assy 
and a 100A contactor.  Although theoretically it should (how much?) have 
worked, I never got to finish the PTT "keying" circuitry.  Wish I 
had........  Finally, sage individuals have told me on various occasions 
that the condition of a dynamotor will effect the in-rush current 
(BGO?).  Further, that new bearings and lubrication may have noticeable 
effect.  Any help?

Regards   Jeep/K3HVG

*  I've been told that the straight, single-breaker, straight PP-4763 is 
more tolerant of surge currents, vice the "A" model with its dual, 
high-sensitivity breakers and that if the breakers in the "A" model were 
removed and replaced with SB fuses, they too will tolerate higher (sic) 
surges.  The efficacy of this fix was never pursued, in my case, nor do 
I believe it would solve the all-dynamotor in-rush issue