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TECH : 1702a Eprom Voltages

Hi All,

I have in a 1978 model pinball machine, one 1702a.


I would like to backup it contents, but my eprom programmer works with
2716 and later.


My question is -


When I probe the cpu board with a scope, around the eprom, I was
expecting to find 5, -5 and -12.


I only find +5 and -12.


Can I power this device from an external -12 and make a adapter to then

read its contents like a 2716.


I can then program a 2716 and using a couple of sockets, rewire for the

2716 in place of the 1702a.


Any help appreciated.


Kind Regards, Garry
 
J

J.A. Legris

Jan 1, 1970
0
Hi All,

I have in a 1978 model pinball machine, one 1702a.


I would like to backup it contents, but my eprom programmer works with
2716 and later.


My question is -


When I probe the cpu board with a scope, around the eprom, I was
expecting to find 5, -5 and -12.


I only find +5 and -12.


Can I power this device from an external -12 and make a adapter to then

read its contents like a 2716.


I can then program a 2716 and using a couple of sockets, rewire for the

2716 in place of the 1702a.


Any help appreciated.


Kind Regards, Garry

Here's a data sheet for an MM1702A, but it uses -9V not -12.

http://www.jmargolin.com/patents/1702a.pdf

If it's only 256 bytes, just set up a bank of 8 DIP switches for
addresses, some LEDs for output, and read out the contents manually.
For posterity, you may want to have someone take your picture as you do
this.
 
D

Dieter Wiedmann

Jan 1, 1970
0
I only find +5 and -12.

Should be +5V and -9V. Datasheets from Intel and MOSTEK are
available here.

Can I power this device from an external -12 and make a adapter to then

read its contents like a 2716.

Better you make an adapter generating -9V from +5V, simple job for
the MC34063A. Later EPROMs, like 2716, do just this on chip.


Regards,
Dieter
 
Thanks guys,

I will attempt to use a small Z80 trainer I have and wire in a dc-dc
converter to get -9 from this 5volt only system.

This is a handy little system that allows direct connections to the bus
via a breadboard.

Regards, Garry
 
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