Thanks Greg Burnett and Frank Stellmach -- good suggestions. I should
have provided a bit more info. On power up, the display usually shows:
-OVLD DCV
Then when I run self-test, I most often get the 209 error.
The CAL? values are good, which is reassuring. I'm thinking it's in
the DC front-end somewhere as Greg suggested.
Frank, this instrument came to me completely untested and not powered
up by the seller -- the power button and actuating shaft are missing,
which makes me think it was in a lab or ATE setup where an accidental
power off would cause big problems. It is in generally very good
physical condition and is very clean.
I don't have schematics for this box. I do have a right-of-return for
refund, which I will most likely exercise.
Best,
Dick Moore
On Aug 1, 2009, at 11:28 AM, [email protected] wrote:
".. internal overload: 72" might be caused by a failure on
calibration,
as '72' might refer to the 'dcv 10V gain' (see calibration manual p.
5-6).
Either an ACAL failed, caused by interrupting this process, or an
attempt to calibrate the internal 7V reference has gone wrong, also
because of interruption, or because of unstable / inappropiate
external
voltage reference.
Please read out cal constant 72 by "CAL? 72", on my instrument it's
1.00435...
If you scroll the text to the rightmost, an additional string states
if
the calibration constant is valid.
Then read out cal constant 2 by 'CAL? 2', that's the internal 7V
reference. Should be betw0en 7,0V and 7,5 V, acc. to LTZ1000
datasheet,
but typ. around 7,2V. It's 7,2165..V on my 3458A. Again, scroll the
text
righmost, if the constant is valid.
If 7V ref constant is corrupted or out of range, a basic calibration
might help.
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