[AMRadio] 75A-2 power consumption

D. Chester k4kyv at charter.net
Sat Feb 21 17:22:49 EST 2009

Don't sweat or nitpick the power consumption.  Bring it up slowly with the 
variac if you have one, and if it doesn't blow a fuse or show abnormally 
high current drain as you go, bring it on up to the full line voltage.  If 
it still hasn't blown a fuse, listen for hum, in case the electrolytics have 
fizzled.  If all is OK so far, check to see if the VR tubes are ignited.  If 
so, everything is probably go.  If not, measure voltages and see why the 
power supply output voltage is below normal.  The normal power consumption 
of a receiver like that should be somewhere between 75 and 100 watts.  That 
means about 1 amp of line current.

If you don't have a variac, just make sure the proper line fuse is in place 
and hope it doesn't blow when you apply power.  A bank of  3-5 100w light 
bulbs in parallel could be inserted in series with the line cord as a 
current limiting resistor the first time it is fired up.  If it pulls a 
little too much current the first time it is turned on, once the 
electrolytics have re-formed, the power drain should decrease down to 
normal. The main thing to worry about is that something might be shorted and 
damage the rectifier tube, power transformer or both the first time it is 
powered up if no precautions are taken.  But that's what the manufacturer 
put a line fuse in the circuit for. Once it passes the smoke test, be gentle 
with it until it accepts full line voltage without abnormalities.

Don k4kyv


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