I installed a new voltage doubler to power the signal tube heaters, that used schottky diodes. A few days later, the primary melted down. Nothing connected to the secondaries was damaged. Post mortem, testing with an external supply, currents still seem in spec (600ma for all 5 tubes)
Simulating, I noticed spikes as high as 6 amps in the heater secondary, though using generic silicon diodes instead showed similar spikes. Could that have fried the transformer, or was it a coincidence?
Simulating, I noticed spikes as high as 6 amps in the heater secondary, though using generic silicon diodes instead showed similar spikes. Could that have fried the transformer, or was it a coincidence?
I wanted the option to raise the heater voltage from 11v to 12.6v. The drop across them is less, and they were recommended in a couple of circuits I've seen for mods of the Dyna PAS power supply.
I would think a current spike from the doubling capacitors would not generate enough heat to melt a power xfer primary wire. An prolonged internal short on the capacitors or the heater circuit might do it. I would also look for possible short circuits.
Did you have a fuse on the power transformer?
Did you have a fuse on the power transformer?
Putting a fuse on the primary would have been my next project! I'm on a short hunt, but some of that will have to wait while clean vaporized transformer varnish off of everything.
HOW is that possible?
What about the primary fuse?
You probably had a full short on the main secondary and an oversized or bypassed mains fuse .
It's no point to raise the filament voltage, it only increases the load on
the tiny transformer.