Time to put the newly built voltage references to work. All my DMM's are way overdue for calibration except the Fluke 8810A and the Siglent SDM 3055. The 500VDC reference isn't ready but “half” of it is at a stable and accurate 250VDC. So I decided to use it and it will be applied to the 750VDC/1000VDC ranges. Not ideal but better than nothing.
Started the calibrations. 3 done and about 7 more to go.
First up. Fluke 8000A. If you recall this was the unit that had the poorly designed power supply resulting in significant drift. I redesigned the power supply and eliminated the drift. All it needed was a slight tweak of the 190.0mV but all the other ranges were OK.
Next. Fluke 8010A. This one was a surprise. When I bought it 2 years ago the DCV was way off and the ACV completely dead. The DCV thin film input divider was somehow damaged. I removed it and built up a replacement of discrete 0.1% resistors. The ACV issue was a bad tant. Despite those significant repairs this guy was well within limits on all ranges so there were no adjustments required.
Fluke 8600A. This one has also had significant repairs in the past year to fix drift issues. But everything was within limits except the 1000VDC range as shown. Now it's OK.
That's it so far. Volt-nut at work.