[volt-nuts] HP3468A

[Roy Phillips]

Bob
Is it possible that this  has been left in the "calibrate" mode ?   I seem 
to remember that there is a DIL switch at the rear (number 8), for this 
purpose. This is of course an instrument that is equipped with HP-IL, which 
makes it a little less attractive, but otherwise a very well made DVM. Good 
luck.
Roy


--------------------------------------------------
From: "Bob Smither" <smither at c-c-i.com>
Sent: Sunday, August 28, 2011 6:08 PM
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
Subject: Re: [volt-nuts] HP3468A

> gbusg wrote:
>> Neil's suggestion (to check the power supplies) is a good one.
>>
>> Make sure the +5V, -15V and +15V rails are correct - and use an 
>> oscilloscope
>> to check for excessive ripple.
>
> Done.  All the supply rails look good.
>
>> You didn't mention if you have the rechargable battery option (opt. 001),
>> but if so, that adds to the number of possible problems.
>
> The unit does not have that option.
>
>> I definitely would replace the 3 volt lithium cell (BT551) ASAP.
>
> I did this, but no change.  I wonder if the boot process is assuming
> something that has been lost from the RAM.
>
>> Also make sure that the front panel "Reset" button isn't stuck in the
>> pushed-in position.
>
> Reset button?  Don't see that.
>>
>> If you're lucky, doing all the above will lead to a cure. If not, then it
>> sounds like some other fault is still causing the "RESET" line (at U501) 
>> to
>> keep cycling. It doesn't sound like you're getting through the turn-on
>> self-tests far enough to see possible further error codes (e.g., 
>> Calibration
>> RAM error, or RAM error, or ROM error, or A/D converter error).
>
> Agreed.
>
>> Let us know how you come-out on it.
>
> Will do.
>
> Thanks for the feedback!
> -- 
> Bob Smither, PhD                                   Circuit Concepts, Inc.
> =========================================================================
> Blessed is he who expects no gratitude, for he shall not be disappointed.
>   -- W. C. Bennett
> =========================================================================
> Smither at C-C-I.Com  http://www.C-C-I.Com  281-331-2744(office)  -4616(fax)
>



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