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

Steve steve-krull at cox.net
Tue Nov 8 00:07:04 UTC 2011


I have the images from the chips in my 3458A. They had '94 dates so a few months ago I unsoldered them, read them, installed machined-pin sockets and burned new chips, and the meter came up with no problems. I hope to send it to Loveland soon. I'm on the road for the week but have asked a fellow ham to send me a copy of the files as we did the reading and burning at his place.


Sent from my iPad

On Nov 7, 2011, at 5:23 PM, "J. L. Trantham" <jltran at att.net> wrote:

> 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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