Re: HP-67 problem Message #7 Posted by Tony Duell (UK) on 19 July 2002, 1:55 p.m., in response to message #5 by Achim
Both chips are HP-custom parts so you can't go and get them from the local electronics shop. The ROM0 is unique to the HP67. Although other machines (Woodstocks, Topcats) use a similar combined ROM0 and display anode decoder, they contain different code, so can't be used in a 67.
The ACT chip can be obtained from a number of machines, though. I think the one from any Woodstock _apart from the HP27_ or any Topcat is worth trying. I've swaped them round in the past and had the machines work correctly. It certainly won't damage anything to try it.
The HP27 is strange, the chips are NMOS, not PMOS (as in all the other Woodstocks, 67, Topcats), so the power supply polartity is different too. Don't try that chip in a 67.
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