paddy ryan
Member
Testing an old B&H 613 AC silent projector after a problem.
.Checked and cleaned, and noticed that the motor now runs perfectly on test from a DC power supply unit, starting at only 25 volts (the projector is 240 volts), but when I connect the projector to an AC variac at the same 25 volts on test, the motor fails to operate. I ramped up the variac voltage to 50 volts, then 75, but no movement, although the little inspection bulb on the projector stayed alight in all tests. Got me flummoxed. Why does the projector only work on the DC power supply unit? Its a very old projector (1945ish), but simply constructed, no transformer. Any advice please? Oh, the projector has an AC/DC switch, but switching to DC on test has no effect whatsoever, only seems to work from the DC power supply unit, which is limited to 30 volts.
.Checked and cleaned, and noticed that the motor now runs perfectly on test from a DC power supply unit, starting at only 25 volts (the projector is 240 volts), but when I connect the projector to an AC variac at the same 25 volts on test, the motor fails to operate. I ramped up the variac voltage to 50 volts, then 75, but no movement, although the little inspection bulb on the projector stayed alight in all tests. Got me flummoxed. Why does the projector only work on the DC power supply unit? Its a very old projector (1945ish), but simply constructed, no transformer. Any advice please? Oh, the projector has an AC/DC switch, but switching to DC on test has no effect whatsoever, only seems to work from the DC power supply unit, which is limited to 30 volts.
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