UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

G8UWM-MildMartin · 11th Feb 2018, 3:15 am

The transformer in my HRO PSU also frizzled about 35 years ago.
But the choke was OK. I don't recall finding the capacitors shown on the diagram between HT and heaters or to the mains input.
But I do remember my replacement transformer having only a 4-V heater winding and 250-0-250-V HT windings and room for enough turns of ordinary 3-A rated PVC-insulated wire to give around 6.7V (to allow for loses in the umbilical, as per the manual) and using silicon rectifiers in choke-input configuration to get the HT down to something reasonable without sweaty resistors.

11th Feb 2018, 3:15 am	#3
G8UWM-MildMartin Heptode Join Date: Jan 2004 Location: Stockport, Greater Manchester, UK. Posts: 827	Re: National HRO PSU. Capacitor values. The transformer in my HRO PSU also frizzled about 35 years ago. But the choke was OK. I don't recall finding the capacitors shown on the diagram between HT and heaters or to the mains input. But I do remember my replacement transformer having only a 4-V heater winding and 250-0-250-V HT windings and room for enough turns of ordinary 3-A rated PVC-insulated wire to give around 6.7V (to allow for loses in the umbilical, as per the manual) and using silicon rectifiers in choke-input configuration to get the HT down to something reasonable without sweaty resistors.