13-02-2014, 10:24 PM
Lawrence has got it close to my proposed circuit for a little Marconi radio that was once owned by my great aunt.
The HT diode in my case is a valve but the rest of the circuit is as I will be testing it.
The HT load uses the positive half cycle of mains and then the negative half cycle operates the heaters.
Should the heater diode fail short circuit the protection diode conducts and blows the plug fuse.
If one fails you would be best off to replace them as a pair.
Use the higher powered 1N5406 type diodes due to the inrush from the cold heaters during switch on.
The HT diode in my case is a valve but the rest of the circuit is as I will be testing it.
The HT load uses the positive half cycle of mains and then the negative half cycle operates the heaters.
Should the heater diode fail short circuit the protection diode conducts and blows the plug fuse.
If one fails you would be best off to replace them as a pair.
Use the higher powered 1N5406 type diodes due to the inrush from the cold heaters during switch on.
