Yeah. It's an HP8920 calibrated at a friend's house with his GPS reference 6 month ago. I picked up another oven from a Micor at a hamfest over the weekend. I'm gonna try that tonight. If it's still off, I'll drag the monitor back to his house for another calibration. I really wish I had kept that rubidium standard I sold a couple years ago
The FTR probably didn't take into account that this crap might just happen to be a little off 25 years later. However, if the crystals were fine-tuned at the factory with graphite, they will age.
Just dawned on me that I could check the heater lines with a amprobe. Might try that first to see if it's working.