My 8569B spectrum had several problems that I ended up repairing, but most were related to adjustments. Now the analog or digital display and traceDATA via GPIB have the same values. Flatness and precision are good tested up to 18.5GHz (limit of my RF generator). Noise floor was between 3 to 5 dB better than specifications measured at the end of each band.
The REFlevel button had two problems, the first: four levels had no effect, it was the rotary switch that had lost a group of 4 contacts that I found at the bottom of the frame, I had to disassemble everything the mechanical assembly of this control, but I ended up repairing it.
The second problem was that the potentiometer for the REF Level 0 to -12 dB variation was very intermittent. I tried to repair but I did not succeed. So I replaced the 10k linear potentiometer by a 20k that I shunted a 20k resistor to have 10k and I made a slight mechanical adaptation by adding spaces on the mounting screws because of the length of the shaft. However, the mechanical stroke of the new potentiometer is not enough to cover 12dB of range as the original, it only covers 11.7dB max. The BCD decoder rotary switch therefore displays from 0 to 11dB only.
HP's part number is 2100-3625, it's a 10k 5% lin wirewound potentiometer, I've evaluated the mechanical displacement at around 320 degrees. I found on eBay this potentiometer but the price is 215 $ USD delivery included or about 271 $ CAD for me, I think that it's very expensive for a potentiometer.
The question: Would anyone know an original or equivalent to this potentiometer at a reasonable price ?
The best equivalent I have found so far is at Digikey, a 10k wirewound potentiometer 5% 20ppm / 'C 2W, mechanical rotation of 330 degrees ±5%, 140B00103-ND (Vishay 140B00103), it is 55.21USD or 76.59 $ CAD...