Good place from which to order 27256 EPROMs ?

Upgrade or replace the ROM.
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Petari
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Good place from which to order 27256 EPROMs ?

Post by Petari » Mon May 07, 2018 9:50 am

I see that it is still available, although here, in Hungary not really. Anyone can recommend good source ? OTP version is OK too.
As I see, it goes straight into 6-chip, 28-pin sockets of STs. I certainly did it some 30 years ago, but was not sure now, so looked schematic.
Better would be to go on 2 chip solution, but early STs have no 74LS11 for it, so I guess that 6 chips will not cost more afterall - no need for some extra board and soldering by users.
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troed
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Re: Good place from which to order 27256 EPROMs ?

Post by troed » Mon May 07, 2018 10:01 am

Petari wrote:
Mon May 07, 2018 9:50 am
I see that it is still available, although here, in Hungary not really. Anyone can recommend good source ? OTP version is OK too.
As I see, it goes straight into 6-chip, 28-pin sockets of STs. I certainly did it some 30 years ago, but was not sure now, so looked schematic.
Better would be to go on 2 chip solution, but early STs have no 74LS11 for it, so I guess that 6 chips will not cost more afterall - no need for some extra board and soldering by users.
I recently bought a bunch from here: https://www.ebay.com/itm/10PCS-IC-27C25 ... 2749.l2649

(they are, "of course", not _new_ .. )

Most were indeed ST 27C256B, some were from a different manufacturer (TI, still stamped ST so "fake") and a few I couldn't get to work at all. The seller has sent new ones without fuss though, waiting for them now.

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