[Amps] Alpha 87A Power Supply Question

[Steve London]

On 05/06/2021 01:03 AM, gudguyham via Amps wrote:
> Some of the old Henry amps actually require a neutral to be present when using the amp on 240v.  On 120v it makes no difference because if you have two wires, hot and neutral (120v) the neutral is available.  When switching to 240vac if you lack the neutral, they instruct you to use ground to carry the fan, and low voltage transformer neutrals.  This practice is NOT good and could be dangerous.  The neutral that is required is hooked up to a separate terminal at the rear of the amp, this is the neutral being sought out by the fan and LV transformer.  The simple fix which satisfies all conditions is to NOT use ground( the green wire) to this terminal as a neutral, but rather use a jumper wire at the two terminals that series up the dual primary to that terminal.  By doing this there is no need for an external neutral and the green wire can be used as chassis ground as intended.

If I correctly understand what you are saying, this is exactly what the Alpha 76 
and my old B&W PT-2500A have done. They have dual 120 volts primaries that they 
put in series for 240 operation. 120 volts for the blower is derived from one 
side of a 120 primary and the "center tap" between the two 120 volt primaries.

73,
Steve, N2IC