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The Vintage Voltage Device allows the user to select the voltage for a vintage amplifier. Settings are:
1. 0 Volts (off)
2. -12 Volts (about 110 VAC)
3. -6 Volts (about 117 VAC)
4. Line Voltage ( 120 - 125 VAC )
The unit provides EMI filtering, spike protection, and fused input and output. Both neutral and hot conductors are disconnected by the on-off switch. Both Neutral and Hot legs are fused. The 12VDC power supply is separately fused.
In addition, the Device will set an alarm if the ground is absent or if the polarity is reversed. The latter condition is exceedingly dangerous and all too common. Reversed polarity at a wall receptacle can cause fatal electrical shock.
The Vintage Voltage Device is experimental, and I will not be reproducing it for sale. It is, however, An essential tool for musicians using vintage (Tweed, Blackface) amps.
For that reason, I am providing here (see below) the schematics, layout, parts lists, and notes for those experienced builders who want to make their own Vintage Voltage Device.
VER F of Vintage Voltage is below. It corrects an issue where the alarms did not sound separately, and in fact only one alarm, the reversed polarity alarm, sounded for both hazard conditions (no ground and reversed polarity).
The VER F design uses three fewer miniature relays. There is a single flashing LED and alarm horn that signals when either a Reversed Polarity or Missing Ground condition exists.