01-05-2016, 11:02 AM
Removed the mains transformer this morning and cleaned it up.
I think I now know why it overheated.
From manufacture the two 4 volt windings have been connected transposed, there is one @ 1.6 A for the rectifier, one side should have been the HT take off, and the other winding is 6 A for the rest of the heaters, one side should have been grounded. They were connected to the wrong heaters! So the 5 valves and lamps which add to 5 A were on the 1.6 A winding! Not very clever is it?
I have had the transformer running on the mains with the core earthed but screen floating for a couple of hours without any load and it has not overheated or got any significant leakage to earth. Voltages are what would be expected. Think I may put it back in, wire it up correctly, leave the screen unconnected and see how it goes.
General standard of the wiring and component fixing is deplorable, not surprised they ceased production. A birds nest of strung up components, metal cans of capacitors with earth wires soldered to the cans, earth wires just soldered to the chassis without tags everywhere, no mechanical joints on wires, just tagged on with solder, not pretty. Not found a single tag strip yet.
A far cry from Bush standards of wire wrapping and soldering.
I think I now know why it overheated.
From manufacture the two 4 volt windings have been connected transposed, there is one @ 1.6 A for the rectifier, one side should have been the HT take off, and the other winding is 6 A for the rest of the heaters, one side should have been grounded. They were connected to the wrong heaters! So the 5 valves and lamps which add to 5 A were on the 1.6 A winding! Not very clever is it?
I have had the transformer running on the mains with the core earthed but screen floating for a couple of hours without any load and it has not overheated or got any significant leakage to earth. Voltages are what would be expected. Think I may put it back in, wire it up correctly, leave the screen unconnected and see how it goes.
General standard of the wiring and component fixing is deplorable, not surprised they ceased production. A birds nest of strung up components, metal cans of capacitors with earth wires soldered to the cans, earth wires just soldered to the chassis without tags everywhere, no mechanical joints on wires, just tagged on with solder, not pretty. Not found a single tag strip yet.
A far cry from Bush standards of wire wrapping and soldering.
Boater Sam.
