[volt-nuts] [Bulk] Re: 3458A reference boards on ebay

[Hendrik Dietrich]

Well, sounds like you already prepared against some of my suggestions.
Still there are possibilities to troubleshoot it - i cannot neither see 
that you checked everything I listed nor that my list is complete and 
you had much bigger ideas.
The datasheet gives some figures telling how much some influences, like 
R variations (and as a result I variations) get supressed on the output -
I would go hunting for nodes where the noise bursts are biggest if all 
preventive actions failed. Up to a certain point, troubleshooting is fun.

Hendrik


Am 29.01.2015 18:22, schrieb Randy Evans:
> The reference module is in a metal box and uses an external linear PS with
> internal separate regulation.  I don't think its external EMI, but anything
> is possible.
>
> Randy
>
> On Wed, Jan 28, 2015 at 10:28 PM, Hendrik Dietrich <don_hendi at gmx.de> wrote:
>
>> Am 29.01.2015 04:07, schrieb Randy Evans:
>>
>>> I bought two HP-3458A ref boards from John Daly (he no longer has any
>>> more)
>>> and they worked fine but have intermittent noise bursts.  I suspect they
>>> were rejects from HP/Agilent.  At some point I will probably replace the
>>> LTZ1000As and reduce the internal temperature set point for better
>>> stability.  Has anyone else had any issues with these units?
>>>
>>> BTW, I packaged the units in an enclosure for a stand-alone reference and,
>>> except for the occasional noise bursts, seem very stable according to my
>>> HP
>>> 3458A and fluke 732A/ESI RV722 KVD.
>>>
>>> Randy
>>>
>>>
>> Hi Randy,
>>
>> Noise bursts, especially if they get back on track again, sound like
>> electromagnetic interference from your short description.
>> If applicable, turn of the CFL or LED lighting, replace the switch-mode
>> power supply with a linear one or even better a battery, try a known
>> non-reject in place of the ebay reference module, spread some capacitors
>> on/around the module and/or invest in a metal box.
>>
>> Hendrik
>>
>>
>>
>>
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