Re: Trying to bring back a AA501


Eric
 

I'll check tonight when I get back to the bench if there is voltage in the
socket with the ic removed. When I curve traced the outputs with the chip
out on a bread board referenced to ic ground point 1 2 and 4 showed a
diode. 3 showed nothing fully open circuit.

On Mon, Jan 6, 2020, 11:41 AM Dave Wise <david_wise@...> wrote:

That happened here a few weeks ago. Fluke 8000A DMM. After a transient,
it would only display even digits. Turned out the 7447 display driver
developed an internal short on its 1's input. The MOS A/D chip was fine.
Whew!

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Chuck Harris
via Groups.Io <cfharris=erols.com@groups.io>
Sent: Sunday, January 05, 2020 10:36 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

I am having trouble imagining how a 15V CMOS device could spontaneously
generate 5V on one of its outputs.... I can see ~0V, or ~15V, or even 7.5V,
but 5V is an odd value for a device that has no resistors in it.

Are you sure that it isn't being bullied around by whatever it is driving?
old style CMOS has very little drive capability.

-Chuck Harris






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