[volt-nuts] 3458A reference boards on ebay

[Will]

The boards are factory rejects.

I bought five of them several years ago when the price was around $40.

One of them had the heater transistor flipped. Worked fine after
reversing the transistor. One had misaligned connector, which would
have been easy to repair but the HP policy seems to be reject rather
than repair small boards. One had corner of the Vishay resistor
cracked.

Two of them were cosmetically perfect but had much higher noise than others.

Be prepared that there is always something wrong. Could be a good idea
to prefer those with some obvious cosmetic problem...


> I am puzzled why there are so many reference boards that are supposed to
> come from 3458As on the used market. It makes me wonder if they are
> genuine.
>
> One seller,  with the two high stability reference boards at $750, claims
> that they come from working and recently calibrated 3458As. Why would
> anyone wreck a working and recently calibrated 3458A?
>
> It is not beyond the bounds of possibility that a 3458A might be worth more
> in parts than as a complete unit. I know this is true for some HP items,
> but I doubt that is the case with a 3458A.
>
> Another seller,  who has them at $395 "or offer", has sold 17 and has 11
> left.
>
> Although expensive,  having two and monitoring the difference between them
> would probably allow their stability to be measured with a DVM of modest
> specification.
>
> There are lots of counterfeit components around,  and I fear that it could
> be some of these boards could fall into that category.  This makes the
> building a board from new components more attractive.  In the short term it
> is likely to be less stable than an old reference,  but at least one would
> know the history of it. If the components were sourced from reliable
> sources, it would get around the  potential counterfeit problem.
>
> Dave.
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