[MRCA] T-195 Power Supply

[W7QHO at aol.com]

In a message dated 11/27/05 4:26:42 PM, ka8wtk at raex.com writes:


> What are you guys using? Batteries? Batteries and a charger? A regulated 
> supply? Some combination of all of these?
> 

Bill,


As mentioned before, depends on whether or not your T-195 has dynamotors 
installed or the later solid state replacements.   The difference is that the 
electromechanical units require a supply capable of providing a high initial 
starting current surge, something on the order of 150 amps or more for a few 
milliseconds.   The solid state units don't exhibit this characteristic so if your 
195 has these a 50 amp switching PS will do the trick.   I see units in this 
category at 'fests and on eBay frequently but the catch here is that some 
switchers are also great RFI generators.   

Many units have shown up on the surplus market with one of each, typically a 
solid state 1000V unit but retaining the smaller electromechanical dyno 
(+250V, -45V & 115vac 400cycle outputs).   Even the small dynamotors exhibit a 
starting surge so a switcher alone may not work.   One way around the surge problem 
is to float a couple of 12 volt batteries connected in series across the 
output of the switcher (or other MIL/commercial PS that can't handle the initial 
grunt).   The batteries should be isolated from the PS by a suitable diode to 
prevent current from flowing back into the PS when it's turned off.   

It's also possible to use a pair of lower current supplies with the T-195.   
The load is neatly split at the input socket, one side going to the HV supply 
only and the other side to the rest of the set.   I ran a 195 for several 
years with a 30amp switcher feeding the solid state HV side and an unregulated 
"brute force" supply (see below) running the rest of the set including the small 
dynamotor.

I currently use a single, simple home brew supply consisting basically of a 
variac, husky transformer 30 vac out @ 100A), solid state bridge rectifier and 
about 200,000 mfd of filter capacitance.   No floating batteries.   Works FB 
driving my BC-375, ATD, TCS and GRC-9 dynamotors as well.

Dennis D. W7QHO
Glendale, CA