Additional sockets are for extra RAM for option 001. It is useful in digitizing applications if you need it. You can just buy usual SRAMs to add it. No need Dallas NVRAM for extra memory.
Calibration data indeed stored in lonely DS1220. You can backup it for history reasons. I would also recommend replacing electrolytic caps on A4 and A6 PSU boards, and Shaffner mains filter as preventive measure. Latest firmware for 3458 is Rev9, you can find caps BOM and firmware dumps on my site at /fix/hp3458a/ . After this I strongly recommend to run meter for 3-4 weeks 24/7 and log SN18 service note calibration values , in sequence - store values, run ACAL ALL, store values again. This test can help you to determine if your meter have bad ADC (can be fixed only by replacement, typical issue with 3458s) or other problems with stability, like big DCV tempco. Typical 3458A have tc about 0.2-0.3 ppm/K, but some gems like mine have that below 0.05 ppm/K for 10V range. If you want to keep meter for metrology purposes, you can opt in to modify A9 LTZ reference for lower oven temperature. That will help you to obtain <2 ppm/year stability at expense of extra noise and invalidated calibration. BR, Illya xDevs.com On October 26, 2019 6:45:28 PM EDT, Didier Juges <[email protected]> wrote: >NVRAMs are Dallas parts with date codes of 2009 and 2010, which >explains >the 1934 CALRAM BATTERY sticker on the back of the instrument and may >be >the reason it was discarded. The next cal was going to be expensive. >Not >socketed. > >There are 4 empty sockets next to the NVRAMs, is that for optional >firmware? > >Are you saying only the 2kB part contains cal data? > > >On Sat, Oct 26, 2019 at 5:35 PM Didier Juges <[email protected]> >wrote: > >> Thanks Frank, it seems like it's time to take the covers off and >figure >> out what I've got. >> >> On Sat, Oct 26, 2019 at 3:38 PM Frank Stellmach < >> [email protected]> wrote: >> >>> Didier, >>> >>> if you have the old board with DALLAS RAMs: >>> >>> - make a dump of the CALRAM into a file, as Poul-Henning explained >>> - buy the 2kB and 2x 32kB DALLAS RAMs, available from several >distributors >>> - DS1220AD-120+ for about 11$/€ and DS1230Y-150+ for about 22$/€ >will >>> do the job >>> - unsolder the old RAMs, and solder precision DIL sockets instead >>> - use a programmer like the TL866 to first make an additional >download >>> from the RAM directly >>> - program the content of the old CAL RAM to the new 2kB one, and >insert >>> all three new RAMs, maybe add these four 32kB RAMs for additional >data >>> buffer >>> >>> Alternatively, you can replace the nvSRAMs by FRAMs, description >>> somewhere in eevblog, or at TiN >>> >>> if you have the new board with the SnapHat batteries, you can't >upload >>> the RAM content again, but: >>> >>> - buy 2 SnapHat battery replacements >>> - switch on the instrument >>> - remove the old batteries >>> - insert the new batteries, I would support the PCB with something >like >>> isolated plastics, due to heavy bending forces >>> >>> video and description at M. J. Lorton (not competent at all, but >>> instructive) >>> >>> Frank >>> >>> >>> _______________________________________________ >>> volt-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com >>> and follow the instructions there. >>> >> >_______________________________________________ >volt-nuts mailing list -- [email protected] >To unsubscribe, go to >http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com >and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com and follow the instructions there.
