[time-nuts] HP10811 Double oven, oven jump?

Dan Kemppainen dan at irtelemetrics.com
Wed Nov 26 12:00:46 EST 2014

Hi All,

I've been playing with some double oven HP10811's. I've been monitoring 
the internal oven feedback vs. temperature and noticed something 
interesting last night. There was a sudden step change in internal oven 
feedback voltage. This is the voltage coming from the amplifier 
monitoring the bridge that feeds the heater transistors.

The step change was on the order of two or three times as large as 
normal swings caused by the furnace cycling in the house. The voltage 
was being monitored by a 8Ch ADC card. All of the other voltages on that 
card were stable.

The jump was very small. I don't recall exactly (Not near that unit 
right now), but somewhere around a mV or less. But it was very sudden 
and compared to everything else on that line, or other voltages being 

I'm wondering if there is something going on in there that may require 
attention. Bad solder, cracked trace, bad component???

Any idea what might have caused this?

Has anyone seen anything similar?


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