[volt-nuts] Making a Reference IC

[M K]

On 14/09/2015 12:08, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
> On 13 Sep 2015 09:15, "M K" <m1k3k1 at hotmail.com> wrote:
>> There has been some of those references available second hand from ebay,
> mostly pulled, but some may be counterfeit, so look for sellers with
> pictures showing it as old..
>
> Several sellers have more than 1, but with one photo, so you would have a
> hard time arguing that your board is a fake just because it looks newer
> than the photo. I believe it is standard practice to photograph a genuine
> article but to ship a fake.
>
> In any case, it is probably possible to make a board look older.
>
> A used 3458A fetches several thousand USD, so I find it hard to believe
> that many would be broken for parts. But even if there is a reason 3458As
> are being broken up, why are other parts not showing up as often as  the
> voltage references?
>
> I just looked on ebay for "3458A board" There are 10, of which 6 are the
> voltage reference and the other 4 being various other 3458A boards.
> Looking for "3458A PCB" changes it to 6 references and 2 two other PCBs. It
> seems a bit suspicious to me that the one board that has wider usage than
> the others is available in roughly 2~3 times the quantity of all other
> boards put together.
>
> We why don't we see 3458A front panels, power supplies etc,  showing up
> much - why all the voltage references?
>
> The fact that there seems to be a market for 3458A reference boards
> suggests to me that there would be a market for a voltage reference board
> based on the same chip, but designed as a stand alone board.
>
> I can think of a few improvements over a 3458A board.
>
> 1) Option to run from batteries to keep it as stable as possible when there
> are power failures.
>
> It should also make it possible to ship a board to another volt-nut,
> keeping it powered in transit.
>
> I don't know the power consumption of the reference,  and I am aware that
> there are some issues shipping batteries,  but these seem much more relaxed
> if the battery is inside equipment.
>
> 2) Option to run chip at a lower temperature than in a 3458A, as some have
> claimed is better.
>
> 3) Temperature sensor that recorded min and max temperatures during
> shipping.
>
> 4) Ability to read time board has been powered on.
>
> I for one would buy such a board, if someone produced one, either as a
> blank PCB or populated with components & adjusted. Specialist components
> would be more readily available is there was a number wanted.
>
> Dave
> _______________________________________________
>
A 731 is not the same beast at all as a 3458, it uses a very different 
reference indeed, I was talking about the IC itself in the 731, not 
buying a completed pcb.