On Aug 4, 2009, at 7:29 AM, [email protected] wrote:
Message: 8
Date: Tue, 4 Aug 2009 07:29:15 -0700 (PDT)
From: "Don @ True-Cal" <[email protected]>
Subject: [time-nuts] Another 3458A problem
To: Discussion of precise time and frequency measurement
<[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset=utf-8
Hello,
Seems this is the month for errant 3458A DMMs. I have a unit that
was working fine and passing both the power on and full Self Tests.
The unit has been stored away for a few years and is very clean.
After several days of continuous error free operation, is started
kicking out the error:
?
114 System Error ? multislope rundown error
?
At first, the error was only every few minutes (all default power on
settings) but is now almost constant. I can clear the error and
proceed for a few more seconds. It is also the only error in the
stack.
?
Suspicious of electrolytics, I checked all voltages and ripple on
both outguard and inguard supplies with everything looking good. I
did replaced some caps that showed barely low values. This unit is
11 years old. At this point, I am reasonably sure it is not power
supply related. I am also sure it is not a cal related condition as
I started a procedure and it would not get past the first offset
section ? same error.
?
Does anyone have any documentation of knowledge of this error?
ERRSTR 114 is not mentioned in the Assembly Level Repair manual.
Thanks.
?
DonRegards...
Don
HP, for good reasons, never intended for anyone but themselves to do
component-level repair, but they never expected the 3458 to be the
last of the high-precision DMMs, either, so their expected useful life
for these instruments was not the 20 or 30 years that some have racked
up and are still going. And that's why they don't unpack the error
strings in the docs. "Rundown slope" sounds like it might be a dual-
slope ADC error, perhaps involving a film-type capacitor that has
dielectric absorption problems, but this is a guess that's so far out
in left field that you can't see it from here.
Now don't forget those cotton gloves when you touch the boards, and
*never* clean up the board after soldering.....
Dick Moore
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