[time-nuts] another 3458A error

Dick Moore richiem at hughes.net
Tue Aug 4 17:51:51 UTC 2009


On Aug 4, 2009, at 7:29 AM, time-nuts-request at febo.com wrote:

> Message: 8
> Date: Tue, 4 Aug 2009 07:29:15 -0700 (PDT)
> From: "Don @ True-Cal" <true-cal at swbell.net>
> Subject: [time-nuts] Another 3458A problem
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Message-ID: <353825.97738.qm at web81803.mail.mud.yahoo.com>
> 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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