Another IC I Can't Identify

Brent Hilpert bhilpert at
Sun Nov 11 15:50:04 CST 2018

On 2018-Nov-11, at 1:32 PM, Rob Jarratt wrote:
>> -----Original Message-----
>> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Brent
>> Hilpert via cctalk
>> On 2018-Nov-11, at 11:52 AM, Rob Jarratt via cctalk wrote:
>>> Thanks for all the replies. If that is indeed what it is, then I still
> have not
>> been able to find the source of one of the signals that seems to be
> causing
>> the Reset, every pin I have found so far is an input, I have not found it
>> connected to the output of anything yet :-(
>> Have you tried the reverse? : follow an origin that you know should be
>> controlling reset, such as the power-on indication from the PS, and see if
> you
>> can trace it to the CPU.=
> I have already found that source and it all looks OK. I think I have
> identified another input to a NOR gate that is high and causing the reset,
> but I can't find where it comes from.

Perhaps I'm not clear on what you're saying, I was taking you as meaning you hadn't found a source driving the reset line.
While you've found a PWR-OK signal and it looks good, have you found how it connects to the reset line?

Reset-line arrangements on small machines aren't usually that complicated.
(Usually the power-on signal source is a series RC combination (often with additional discretes such as diodes) between a power-bus and ground).

Perhaps put up an image of the schematic you have so far.

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