10 May
2010
10 May
'10
2:14 p.m.
Hi Chris
A good way to look for such opens ( usually of feed thrus ) is to use a
two input scope and combine both inputs with one of them inverted.
Check the easy ones first, like address and data lines.
Even a non-active line will show a difference in voltage when probed
this way. I've used this on a couple of trouble cases with good
results.
Dwight
Date: Mon, 10 May 2010 10:17:46 -0500
From: chrise at pobox.com
To: cctech at classiccmp.org
Subject: Re: i8355 from SDK-85 flakey
CC: cctalk at classiccmp.org
On Monday (05/10/2010 at 07:18AM -0700), dwight elvey wrote:
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Hi
As was mentioned, there is a different pin on the 8755A than
the 8355 used on the sdk85. Did you check that it was
at the correct level?
Yes... there are several jumper pads on the PCB which you strap differently
whether there is an 8355, 8755 or 8755A in the socket. I strapped for 8755A,
which is what I am using. No joy.
I'm suspecting a micro-fine crack in a PCB trace as the next culprit so I
will soon get back to looking for that.
Chris
--
Chris Elmquist