Thank you for the information, that saved me some ghost hunting for drifted resistors in the meter circuit.
Both the voltage and current adjustment pots are Bourns series 3540 which are rated at 2W.
Voltage Adj: 3540S-419-503 (50K)
There is also another part number on them, which seems to be Tektronix related:
311-0946-00: "Tektronix Test Equipment Potentiometer Precision 10 Turn 50K 5% Lin = .05%, Bourns Part # 3540S-419-503".
Current Adj: 3540S-504-203 (20K)
And also has: 3100-18S7 but search did not lead to anything related.
The replaced 50K voltage adjustment pot has a very thin (about 1/8") shaft, and the current adjustment one has a regular 1/4" shaft. Both have identical looking grey knobs with a black inset despite the different shaft diameters. After comparing them with online pictures of the power supply they are definitively different from the original ones, and only the black meter select switch knob seems to match. Taking another look at those two knobs, they definitively look very Tektronix like and this makes me think that the tech that serviced the power supply might have had access to Tek parts, and chose the 50K and corresponding knob just to make do, and even replaced the knob on the current adjust to match.
Was thinking that will now need to ideally find the equivalent 100K Bourns 3540S-419-104 (if that is an actual existing valid number) with the same 1/8" shaft to match the existing knob. But can't seem to get anything on that PN, neither does searching for 3540S-504-104. Instead all I am finding is 3540S-1-104 which is also 100K with the same linearity specs but with a 1/4" shaft. It does come up at Mouser as Obsolete, but they suggest the alternate 3540S-1-104L ROHS part instead for $34. Ebay also has a couple of options at around $20-$25.
Seems like not going to find anything with a 1/8" shaft, so by any chance does anybody have a pair of the correct original matching black HP 1/4 inch shaft knobs?
