New (to me) HP 3421A DA/C Unit, some questions

[Dave Frederickson]

(05-11-2017 06:52 PM)4ster Wrote:  Now that a new battery is installed on the DAC I get one error on startup under battery power: Error 7, "Failed 10 Mohm test (not within +/- 20%)". I suspect that this might be due to calibration drift. On battery power, if I run the ROM "FP" program it reports an error and halts. Interestingly, this clears the error symbol on the DAC and I can now run the "FP" program again without the error. Is this behavior caused by an old calibration, or something else?

Error 7 is caused by having something connected to the Mux board when the power-on self-test runs. The error symbol is cleared when the four Error Status Registers are read.

Quote:I tested the voltage of the calibration battery when I had the case open and it is 3.1ish volts. Lithiums drop off quickly when exhausted, I suspect this one is nearly there. I am aware of the posts here about how to change the calibration battery on the HP 3468 meter without loosing calibration. Anyone care to offer advice?

The 3421A uses exactly the same battery for the CAL RAM as does the 3468. There are procedures for changing the battery with external battery and AC power applied.
http://www.hpmuseum.org/cgi-sys/cgiwrap/...ead=176914
http://mrmodemhead.com/blog/hp-3468a-bat...placement/

There's an alternate procedure that saves and restores the cal constants and doesn't require powering the CAL RAM while changing the battery.
http://www.hpmuseum.org/forum/thread-8061.html

Dave