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After buying and selling proms and eproms for over 20 yrs, you tend to learn a thing or two,
so I figured I would share some insight on a new [bad] trend I am seeing more often now .... :

Sellers selling chips as NEW, when I know they are not.

This is especially important for [bipolar] proms which can only be programmed once.
(... UV eproms can be erased, so that's not as much of an issue, but still )

Bipolar proms must be new (NOS) in order to be of any use.
[ they can not be re-used if they have been programmed, even just once ]

The problem is that a prom might appear new, but has actually been programmed.

It was not uncommon for some manufacturers back in the day to program 100's of chips to be used
on their electronic devices during production , and oftentimes , many of those chips were never used.

Imagine mass programing 500 proms for a specific device in a production line ,
and then for whatever reason you end up only using 200 of them.

You would have 300 "un-used" chips, but that have been programmed.

Fast-foward 40 years and imagine a chip re-seller that finds tubes of "un-used" proms which look brand new,
and they don't know any better so they sell them as "new" .

Virtually NONE of the sellers on ebay actually test their chips ,
so in their defense, they have no idea that the chips have already been programmed .
Most incorrectly sell them as "new" out of ignorance.

--

The telltale sign of a mass pre-programmed chip is a lot number printed on the chip.

Most proms would only have markings for the prom type and a 4-digit date code, that's it.
If you see other numbers, it is most-likely a specific programming LOT number,
which would indicate that the prom has been programmed with some specific file.

If you look at this eBay auction :


Capture1.JPG

You can see an extra number (circled in red) which looks printed separately from the original markings.
This is classic example of mass-programmed lot number

I would bet 100% that these chips are already programmed and therefor useless.
(... and not only is this seller likely blissfully ignorant about his useless chips,
he's also delusional in thinking that they are worth $32 each ! ;-)

--

I personally try to avoid eBay because the sellers are so clueless about what they are selling,
but it is getting harder to find reliable sources for good proms these days...

So buyer beware...

Cheers,
Steph

www.Hobbyroms.com
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