What is it reading in AC 10V mode? Is it something unreaslistically high like 40V?
That would be an indication the Elantec IC is bad. I would have to look up its U number but it is common.
Hi to all,
..
A tech @ Keysight told me that my 3458a is an older version and needs to be updated with the newest ROM, which is way too expensive to add to the costs already put in.
I suspect a temperature drift or error somewhere... Anyone have an idea? Thanks in advance for any tip 
Please identify your current ROM version, and the number of EPROMs inside your unit, very probably, it's a 6 IC version.
You can program the latest version, 8 or 9 ( no difference) by yourself, at no cost, if you erase the existing EPROMs and reprogram them.
There exist different versions of the firmware in the net, and somebody already had partitioned the newer 1 - chip -versions into 6 files .
All firmware versions will work with your board, and a re-calibration is also not necessary.
This will not cure your ACV problem, but will fix a number of bugs.
You might also equip your instrument with opt. 01, 128k additional memory, by adding 4 x32k RAMs.
The replacement of the CALRAM is also recommended, if its datecode it elder than 10 years.
Frank.
The replacement of the CALRAM is also recommended, if its datecode it elder than 10 years.
Frank.
Before mucking around with the memories, I HIGHLY recommend making a backup copy of the CALRAM data. I wrote a program (based on Poul-Henning Kamp's work) to do this over GPIB. The backup program is now included in ke5fx's GPIBKIT package. Note that you cannot write the calram over GPIB... you will need a device programmer to do that. Once the calram chip is pulled, I'd also back it up using the device programmer... belts and suspenders are a good thing.