Squashed profile toroidal to get in a 1U case of a 1992, Ampeg B1 amp, export version, internally set for 240 V use, blew (violently) the mains fuse. No burnt smell or obvious damage to the transformer. Disconnected and removed there are 2 seaparate primaries , >1000 Meg , 500 volt isolation between them and the secondaries.3 wires to each primary , presumably 110V and 120 V each pair. Measures about 3 ohm over each "120V " pair of separate primaries which seems about right for a good 450 VA transformer. Connect either primary to a 20 volt ac variac supply and they draw 1 amp of current. I could understand a failure in one primary but both failed the same ? Could there be failed VDRs or something buried inside the transformer ?
14 years ago