Dropping B+ voltage in Stereomour II

[gstitt]

I have some excess B+ voltage in my Stereomour II due to a mains voltage that runs about 123-124 volts. I am investigating maybe building an isolation transformer using a Hammond 169G that also allows some voltage step-down options. Another route is to use higher value resistors in the CRCRC supply ( realize I might need to also then adjust the dropping resistors on the 2A3 heater supplies). If I go the latter route is it necessary to increase the two R's in CRCRC equally keeping them at the same value? Or can I increase just one of the R's, and if so, does it matter which one?

Greg

 

[Doc B]

What are your voltages and how much higher are they than the manual specs?

 

[gstitt]

At the 2A3 Plate (Terminals 1,20) my readings are both at 378 Volts. Cathodes (Terminals 6,15) are at 61.9 and 62.5. This is with the stock Sovtek 2A3's and is within range, but on the high side. I am thinking about purchasing some EML 2A3 Mesh tubes and I would like to be, if anything on the low side of the range since these tubes need to be run conservatively for longevity.

Thanks Doc.

Greg

 

[braubeat]

a simple solution would be a variac which would be plug and play and easily adjustable if conditions changed

michael

 

[Paul Joppa]

To address the initial question, the supplied 0.15-ohm filament resistors are optimum at 122v input - no need to fiddle with them in this case. For the high voltage, either or both 130-ohm resistors can be increased in value. Don't exceed 180 ohms unless you increase the wattage rating of the resistor!

 

[gstitt]

Paul,

Thanks so much for the resistor info, and yes my 2A3 filament AC readings are just about spot on now at 2.51 and 2.53 volts.

Greg