[time-nuts] Another 3458A problem

Roy Phillips phill.r1 at btinternet.com
Tue Aug 4 15:02:57 UTC 2009


Don
I have always wanted a 3458A - but I am amazed at the number of faults you 
fellows are encountering with this instrument - -this must make it a very 
hazardous purchase, in particular from a private source !! I have both 3456 
& 3457, which for some years have been faultless - maybe because they are 
less sophisticated ?
Roy

----- Original Message ----- 
From: "Don @ True-Cal" <true-cal at swbell.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Tuesday, August 04, 2009 3:29 PM
Subject: [time-nuts] Another 3458A problem


> 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
>
>
>
>
> ________________________________
> From: Dick Moore <richiem at hughes.net>
> To: time-nuts at febo.com
> Sent: Sunday, August 2, 2009 2:08:08 PM
> Subject: Re: [time-nuts] new request for 3458A info
>
>
> On Aug 2, 2009, at 5:00 AM, time-nuts-request at febo.com wrote:
>>
>> Message: 4
>> Date: Sun, 02 Aug 2009 03:00:06 +0200
>> From: "Dr. Frank Stellmach" <drfrank.stellmach at freenet.de>
>> Subject: [time-nuts] 3458A info
>> To: time-nuts at febo.com
>> Message-ID: <4A74E516.5020202 at freenet.de>
>> Content-Type: text/plain; charset=ISO-8859-15; format=flowed
>>
>> Dick,
>>
>> did you already try an ACAL DCV, or ACAL ALL from the front panel?
>>
>> Maybe the false cal constants will be set correctly.
>>
>> In the calibration manual, its explained, which constants are set by
>> atocal (and cured), and which one are set by basic calibration,
>> requiring external standards (10 volt, 10kohm).
>> I think, DAC Vos and 10V gain are set by ACAL.
>>
>> Frank
>
> Yes, tried all that. Last night I gave up and opened the box, which I had 
> been reluctant to do -- DC board had burned components right in the 
> center. There are 2 unrecognizable ICs and a handful of resistors, etc, 
> and a badly charred board. Probably unrepairable. Have no idea what could 
> have happened to make it so bad without also killing the power supplies, 
> which are AOK. Shouldn't have been anything on the input, which is 
> protected against over-voltage/-current. Too bad.
>
> Thanks for all the advice and tips.
>
> Dick Moore
>
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