So far it seems that all three supplies seem to be delivering adjustable voltage within the ranges they are supposed to, however the meter on the leftmost unit is showing an invalid value and something on the leftmost unit is buzzing, (perhaps the transformer) although nothing seems to be getting hot. Visually it all looks fine. Anyway, if I can get it fixed, it looks like the kind of power supply that I can use for a while, and never grow out of, especially if I replace the caps (although none appear to be bulging). It's good that it has a handle on the side, as it weighs a lot. Almost as much as my scope. This is definitely a linear power supply
. But its perfect for the kinds of things I do, as I like to fool around with radio stuff.
So far no luck on finding a schematic or service manual specific to this XT family of units, despite their popularity. The manuals refer to a schematic in Appendix A which describes the calibration assembly but the online PDFs Ive found so far doesnt contain it! - Just a blank page placeholder where it is supposed to be.
One thing that is intriguing, there are multiple internal headers in each unit, which seems to me to indicate a lot of potential controllability/upgradability. Also, tested the two fully working units accuracy and they are both accurate as far as voltage goes. They have a 10 turn potentiometer for adjusting voltage to very fine accuracy but only a three digit readout for displaying it.
It appears from peering through the space on the side that there are LEDs and a calibration pot under a little shim on the top left panel, but no obvious place to pull at it to remove that plastic.
Looks like I may need to disassemble the panel.