[G0HZU_JMR]

Assuming ~240V AC mains I think the original transformer typically produced 16.5Vrms at the secondary. This would mean the (smoothed) bridge rectifier would give out about 22V DC at light loads. This would mean there would be about 8V across the pass transistors.

At higher load currents this 22V DC voltage at the pass transistor inputs will drop due to losses in the bridge and the various connections and there will be some ripple here as well.

I used similar 1.1degC/W rated heatsinks as the original on my build and I made up an adjustable and switchable load. This was made from some huge 0.47R and 0.22R and 10R metal clad resistors mounted to a big aluminium plate and I still have this load up in the loft somewhere. I recall switching the load in and out and measuring the dynamic regulation from the supply. It was very good even with a harsh test like this. To prevent transient sagging at the output it did require the current limit setting to be set quite high and I think I could rapidly switch between load currents of 1.4A and about 20A in this test.

I do remember that it got very hot at a continuous 15A load current so I'm not sure how well it would perform on a 20A continuous soak test. I'm not sure the original heatsinks are big enough for this test and my old test load certainly wasn't up to it.

However, a typical 100W CW/SSB radio will probably run at a much lower duty cycle even though it will probably gulp current at 20A peak. I don't recall the PSU heatsinks getting very hot when transmitting 100W SSB or CW with an old Yaesu FT707 or a Trio TS430S.