| Electronics > Metrology |
| Keithley 155 restoration project |
| << < (3/3) |
| Rax:
--- Quote from: lowimpedance on November 16, 2024, 05:01:43 am ---Would be interesting to see pic's from inside the 1554 module :) --- End quote --- Here you go! |
| Rax:
--- Quote from: lowimpedance on November 16, 2024, 05:01:43 am ---As for the battery compartment it's the dissolving foam and it's adhesive I had to remove from mine , and from your pictures that is what you have waiting on your unit. Not much fun :-\. --- End quote --- So true. I've spent a good part of yesterday digging into the mess in there. I put a sheet of paper between the messiness and the PCB - I hope I managed to protect the electronics. |
| Rax:
Finished project (the batteries part, that is). |
| Oldtestgear:
Keithley 1554 PSU schematic as requested. Hope this is what you need. My mains PSU arrived with a dud transformer. After a bit of trepidation I replaced it with a cheap transformer without the nice screening & was surprised that it was stable down to the microvolt ranges. Cheers Phil |
| EC8010:
I note that guenthert mentioned that null meters have a high impedance to ground and your power supply diagram shows a mains transformer having E/S screens around both primary and secondary. That typically reduces CPS to <5fF. The significance being that it keeps that high impedance high to mains frequency and harmonics. An off-the-shelf transformer will be >20pF. For sensitive work, you'll want to use battery power. It would be interesting to measure CPS on that dud transformer. |
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