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

[J. L. Trantham]

My conversation with the folks in Loveland led me to believe that they do
almost exclusively component level repair in an effort to preserve the
'character' of the meter.  I also got the impression that they wanted to
minimize uncertainties about parts long term reliability by keeping as much
of the original meter as possible.  When the NVRAM's are replaced, they
unsolder and resolder them using NVRAM's with date codes of less than a year
old.  My understanding of the DALLAS chips is that the 'battery' is not
connected until the first time the chip is powered up.  Therefore, the 'new'
chips should last 10 to 15 years although they consider them in need of
replacement when over 10 years old.

According to the parts list info on the website and Service Note 19A, it
would appear that only the 03458-80047 and 03458-80048 (Opt. 01) variants of
the A5 board are available.  As best I can tell, the 03458-66505 was
replaced by the 03458-69505 which appears to have been a 'refurbished'
03458-66505.  However, when searching for that, it is 'obsolete'.  The only
thing I can find on their site is the 03458-80047 'Update Kit'.

>From my perspective, if I want to have the meter long term, having the EPROM
and NVRAM's socketed would be desirable to permit archiving the data,
reprogramming new NVRAM's when the time comes, and ease of updating the
firmware if needed.  Otherwise, it's unsoldering and resoldering.  I hadn't
really considered the issue of them becoming dislodged from their sockets.

There was/is an issue with some NVRAM batteries not lasting as long as
originally thought, discussed in Service Note 20, and once the data is gone,
if you don't have it archived and can't reprogram the NVRAM, it's off to HP
for repair and/or recalibration at $550 to $2350.

However, perhaps there is a way to harvest the data by HPIB, archive it that
way, and use HPIB to 'reprogram' new NVRAM's without the need to do a 'cal'.
In any event, old NVRAM's, at some point, will have to be removed and new
one's installed.

I am trying to solve the HPIB conundrum now.  It promises to be a fairly
steep learning curve.  All suggestions appreciated.

Joe


-----Original Message-----
From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
Behalf Of Bill Gold
Sent: Saturday, November 05, 2011 11:16 AM
To: volt-nuts at febo.com
Subject: Re: [volt-nuts] 3458A - To Modify or Not To Modify?


Poul-Henning:

    Excellent point that I had overlooked.  But I agree with you that HP
should have used some sort of securing method for the NVRAM.  One good drop
from ye olde UPS brown suit gorilla and it would be all over.  I have seen
these sort of devices that are heavy, strapped in as you point out.  No spec
on how much G force the meter can be subjected to and still work correctly.
I have had 3456A meters calibrated, and upon request Agilent will send you
an empty shipping box designed for the instrument which is just like the
original shipping box when the meter was first delievered.  They certainly
return the meter in this box, no matter what packaging you send it in, to
the calibration facility.  Seeing these boxes I would believe that the meter
would survive most anything short of falling out of the plane at 40,000
feet.

    I guess that then this would affect what Joe would want to do to his A5
board.  Also I doubt that Loveland would take the time to change the NVRAM
on Joe's board, just replace it with a "new" one.  If they would put in an
A5 board with the new surface mount "snap hat" NVRAM then he would not have
anymore problems.  Of course we don't know if Agilent is still making new A5
boards or if they are "refurbishing to factory specs" old boards.  But then
the 3458A is still a current product being sold.  I don't know.

    Since I have my local standards, shipment by UPS didn't enter my mind.

Bill
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