TECH : 1702a Eprom Voltages

Sep 17, 2006 3 Replies

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garrymaroon 19 years ago

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

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J.A. Legris 19 years ago

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

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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.

-- Joe Legris

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Dieter Wiedmann 19 years ago

snipped-for-privacy@optusnet.com.au schrieb:

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

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

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garrymaroon 19 years ago

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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