[volt-nuts] 3458A - To Modify or Not To Modify?

Bill Gold wpgold3637 at att.net
Mon Nov 7 17:31:01 UTC 2011


Joe:

    When I removed my original NVRAM, put in the sockets and then installed the original NVRAM I got a few error messages when I turned the meter back on.  I don't remember exactly what the complaint was but it involved a few calibration constants missing and the calibration password missing.  My initial guess was that the batteries were gone and desoldering the NVRAM just finished the process.  The date codes on the NVRAM was 1989 so I was just running on borrowed time anyhow.

    I don't have a ROM programmer anyhow so I just installed the new NVRAM and did a full calibration to my local standards.  I really don't care about traceability to NIST anyhow.  What I have here is close enough for what I do.

    I have tried to find out what material is used for the pins of the NVRAM is but no such luck from the Maxim/Dallas package datasheets.  My guess would be the usual tin plate.  Yes, gold against tin isn't the best idea, but it is better than tin against tin.  You are simply not going to find these NVRAM with gold plated pins so you have no choice.  I forget whether the gold migrates into the tin or the tin migrates into the gold.  When we specified the plating of the "fingers" of our PC Boards, we used nickel over the copper and then 60u of gold over the nickel.  This gave the best results for constant insertion and removal of the PC Boards from the mother board sockets, which were gold plated.  We produced expensive ATE for Discrete Semiconductors, in the range of $100k to $200k each, so we wanted absolutely, positively good contact all the time and no failures due to repeated removal and insertion.

    IMHO you are on the right track.  Let's see what happens when you finally get the Loveland calibration.

Bill


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