On Jun 4, 9:40 pm, "JA" formula1vhs@ TOGLIMI hotmail.com wrote:
hi guys!
I need to have an obsolete 2708 eprom programmer-reader..
It's very difficult to find modern eprom programmers that do this!
I have buyed a willeim but it does everithing but 2708!!
Well if it's possible i would make one.
I'm very good skinned as electronic handy man , but i can't know how to make
it.
Can someone help me?
And if someone got an old eprom programmer let me know!

The 2708 requires two additional supply voltages, +12 and -5 in
addition to the +5 required by 2716 onwards. That's probably why most
programmers don't support it.

Should not be hard to make one though - I made a 2716 programmer in
high school, and you could probably do a 2708 if you got the extra
voltages. I used an 8255 I/O chip wired into an expansion memory
socket on my Z80 computer; but you could also hang the 8255 off a
parallel port as an I/O expander. Either that, or get a USB-connected
microcontroller with enough I/O pins. For programming you'll need a
VPP supply and something that can generate a pulse of the right width
- back then I didn't want to trust software timing, today you might.
Or you could use a 2716 in an adapter as the replacement and only have
to worry about accomplishing the readout.