(100% !) Verify that reading EPROMs with known contents produces the correct data.Where IC sockets are used: remove & re-socket IC's.Replace electrolytic capacitors on the board (I see only two? 10 uF can be had in ceramic these days, tantalum would also be a good choice here).Do you have a way to read these EPROMs outside the programmer? A few other things to try:
I'd definitely get some more different types of EPROM (27(C)64, 27(C)128, 27C256 without -A or -B, 27512) to get a clearer picture of what's going on. So some bytes DO get written? That means a blank check fails after you've tried a write attempt?Ĭould be a data integrity issue perhaps, a data or address line making intermittent contact, etc. *Furthermore, a read (verify) of the eproms also requires 6,25V +- 0.25V and here I get also into troubles, because the eprom gives inconsistent results when reading the eprom. I don't know if the duration of the program-pulses is a problem. The programming voltage I have is okay (12,55 Volt wich is within the specs of the datasheet =12,75 -0.25V). The problem I think is with the constant VCC of +5V, the datasheet of the eprom says that it should be 6,25V (+-0,25 V) during the programming of the eprom and the datasheet also says that the program pulses should be 100us and my programmer uses 1 ms.
27c512 eprom programmer software#
The software that comes with this eprom programmer only allows me to select the type of eprom (27c64, 27c128, 27c256, 27c512), I can't change anything else. The programmer I use is one that was published in elektuur march 1997.
* The manufacturer of the 27C256B I have is ST microelectronics.
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