Delmar Evans wrote:Do you remember what your unloaded voltages were on your Heyboer? MM transformer is 380-0-380. I'm thinking of changing out to a 350-0-350 or a 330-0-330.
As built in 2013:
Pri: 124.5 VAC
Unloaded DC at 5AR4: 479.8 VDC,
698 VAC at pins 4 & 6
Filament voltage at V1: 6.87 VAC
(698/2 =
349 VAC unloaded)
V4 & V5 Tung-Sol 5881 : 436 VDC plates, 434 VDC screens
Voltage at 220K junction: -48.4, at cathodes, V4: -30.4, V5: -34.8
However, IIRC that PT was wound for a 123V primary and it had the correct range HT rating so that it would load down to around 430V or so with modern mains voltages.
In 2014 a sub station was added close to my home and now mains voltage hovers around 122.4/5 VAC year round. I would imagine if I opened it up, the plate voltages should be several volts lower.
TM