Buoyed by the success on my Power Designs 2005 repair, I've acquired a 0-20V 2 amp model, the Power Designs 2020 Precision Power Supply. Note - this is not the same as the 2020B, and unfortunately, it seems no one has a manual or schematic for this sucker, so repair may be a bit more difficult.
The unit powers up OK, and the oven comes on. However, voltage regulation is not up to snuff. The first thing I discovered is that there is no semiconductor control of the oven heating element; It's mains voltage wired straight up to the thermostat, and relies on this mechanical thermostat to switch on/off mains voltage to the heater. Second thing I discovered is that the thermostat starts switching on/off almost immediately (~40C), but the temperature does not stabilize until around 85C! That was measured with the cover partially removed (so I could insert my thermocouple), so in actuality I suspect the temperature is higher than that with the cover on. Too hot? I think so. I got better results running my 2005 at 50C.
So, disconnecting the heater and just running the thing without the temperature stabilization, it initially looked like I was getting pretty good regulation - around 50 microvolts. However, while I was out of the room, something caused a disruption in the output voltage, as when I came back a bit later, the statistics on my meter showed a drift of several millivolts. The unit looks like someone might have been monkeying around with it. I did check all the caps for short/open, and didn't see any issues there.
I am going to start by rewiring the heater and converting it to use a lower voltage off the secondary. Then I will clean the contacts on the switches and recalibrate, and see where we are at.
Pictures below.