PSU Calibration

[Cheemo]

Just wondering if anyone has had a similar issue.

Went to calibrate the PSU on my vintage mini. Got to +10v easily enough. When I went to dial in -10v it jumped to +7 where it stayed for a while, then it went back to around -10, then back to +7 and now it's stuck there.

Any help would be greatly appreciated.

[VCO]

What year is it?

[Cheemo]

Not too sure. ‘72 maybe?

It’s the second version for sure. Pre 10,000 Serial #. Definitely not the earliest.