[R-390] Line Voltage Survey Results

[Perry Sandeen]

List,

Thanks to all who answered about their voltages, problems and solutions both on and off list.

What I found out.

1.  Line voltage varies considerably from 120 to 130 at different locations, but seems to be relatively stable at the delivered value.  So most will be able to use the 117 or 130 volt tap on the SP 600 and keep the filament voltages within spec.

2. Variacs seem to be a popular solution for some, either manual or some motor driven.  Personally I have never found them nearly as cheap as others on the list.  Bucking transformers don’t seem very popular.

3.  The 124 to 125 volt line voltage is a PITA to deal with.  The 117 tap is too high, the 130 is too low. The simplest solution was sent to me by Bernie W8RPW.

He uses a 10 ohm 10W resister in series with the input as well as an Ametherm SL10300001 which is 30 Ohms Cold, 1 Amp Max Hot or SL10500002 50 Ohms Cold 1.6 Amps Hot.SL10300001.

The Ameritherm units he uses are available from Newark or Digikey.  Both are less than a buck.

I tried just using a 10 Ohm 10 W Wire-wound sandbar and my filament voltage was a smidgen lower than my 5.99 target.  I haven’t decided yet if I want to construct a 9.75 ohm resistor.  I’ll wait until I get a surge limiter and see what I need to fine tune the value.  Maybe with a surge limiter all I’ll need is 9 ohms. TBC.  YMMV.

Regards,

Perrier