11 May
2010
11 May
'10
4:12 p.m.
From: ard at p850ug1.demon.co.uk
Subject: Re: i8355 from SDK-85 flakey
To: cctalk at classiccmp.org
Date: Tue, 11 May 2010 21:38:16 +0100
Hi Tony
With an ohmmeter, it is often difficult to know when the contact is good.
Many times I've seen problems with bad sockets that looked good on the
ohmmeter because I pressed the lead of the IC hard to ensure good contact.
With a scope, you can see visually that the contact is good enough and that no
additional pressure is needed. I don't need a low ohms contact with the
scope lead. A less than optimal contact is usually good enough( especially with
a 10X probe ).
It is also a little faster, especially when running down address or bus leads.
I do use a meter often as well. Once I locate a suspect trace, I use the
meter to pin it down.
Dwight
_________________________________________________________________
Hotmail is redefining busy with tools for the New Busy. Get more from your inbox.
http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:…
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=2C like address and data lines.
How is this better than using a good ohmmeter (with the power off)?
-tony