[GreenKeys] 120VDC power supply noise?

[KC0NNC at aol.com]

If you have a variac, try placing the supply on the variac, and see how  
stable the output voltage is as you run the ac input voltage up and down, If  this 
is a sola unit, then you should see a very small change in the DC output as  
you run the ac mains from 100 to 140 vac input.
 
also, you could place a 1 ohm resistor in the two transformer output leads  
before the ac capacitor and the bridge rectifier, and all the components  that 
follows, and then place the ac dvm, across each resistor, and see what  the 
voltage drop is across each resistor, this will tell you if the  following 
circuitry is pulling excessive current, and what type of  current.  I would also 
try and estimate the supply output voltage and  current capability.
 
 
Lets say it is rated at 110 vdc out at 1 amp.  Then you could use a  100 watt 
incandescent light bulb for a load, and see how the supply  behaves, while 
running the variac up and down.  also try smaller bulbs  to see how it regulates 
under less loading.  etc, etc.  I would  consider leaving some kind of 
resistance into the bridge for surge  protection.  1 to 10 ohms carbon 2 watt 
generally works well, depends on  the required output current of the supply
 
sort of fun qualifying power supplies in this fashion.  I once had a 4  kV @ 
1 amp.  DC supply for an Eimac tube I needed to check out, and series  the 
appropriate number of 1 amp.  120 vac bulbs (about 40 of them)[cheap  enough at 
$0.25  ea.}  set them  on a plywood board, and ran it  for an hour or so... 
confirming the supply was ok,  then went on to find  the bad tube socket under 
the 4cx3000 Eimac tube.
 
At 60 years of age, I can attest that I was, and continue to be, quite  
careful while working with these voltages and currents.
 
73's
Harvey E.  Smith, KC0NNC
2020 Baculite Mesa Road
Pueblo, CO., 81001-2456

719  406 9735, 719 671 2671, 719 546  1418

zzzz/ryry