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

[J. L. Trantham]

Bill,

I don't know if I have damaged my 'cal' DS1220Y or not.  The two DS1230Y's
had files that looked like what I was expecting when I read them.  On the
DS1220Y, the original read on my BP-1600 gave an over current warning and
shut down.  The chip was a bit warm from the unsoldering and, perhaps, that
was it.  I then moved it from my BP-1600 to an Advin MVP and it read
promptly.  I then re-read it on the BP-1600 and it read promptly.  So, don't
know.  Would be nice to find an image to compare with just to get an idea
about what it should look like.

That chip had a date code of 9713 and the two DS1230Y's were 9703.

In any event, new sockets and chips are on the way.  If I have lost my
calibration constants, I would anticipate that the meter is still 'calable'
which is what I am hoping for.  Then, once it gets back from Agilent, I will
be able to harvest the data from the new chips, archive it, and be in
business the next time the chips fail.  Then, again, my current chip may
still be OK.

Joe

-----Original Message-----
From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
Behalf Of Bill Gold
Sent: Monday, November 07, 2011 11:31 AM
To: volt-nuts at febo.com
Subject: Re: [volt-nuts] 3458A - To Modify or Not To Modify?


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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