Date : Mon, 01 Nov 1999 12:11:24 +0100
From : "Mark Usher" <marku@...>
Subject: Re: Further investigation
A singed finger tip, and a stiff neck later...
> You should get fairly good results just checking them in circuit
> without doing
> anything special. But yeah, I'd look for dry joints first.
Checked round and everything seems to be fine.
Did a some multi meter tests... and did them again after disconnecting the
econet lead...
bad bbc good bbc
IC95 pin 5 - IC94 pin 5 66.2Kohms 72.6Kohms
IC95 pin 5 - IC95 pin 10 86.4Kohms 87.4Kohms
IC95 pin 7 - R61 996 1011
IC95 pin 12 - R61 996 1011
IC95 pin 9 - R64 29.88K 33.0K
IC95 pin 4 - R64 29.88K 32.7K
IC94 pin 4 - R41 99.6K 98.9K
IC94 pin 5 - R40 99.4K 99.5K
IC94 pin 4 - IC94 pin 12 10.53K 10.76K
IC94 pin 5 - IC94 pin 12 10.00K 10.8K
IC94 pin 12 - R46 1000 996
IC89 pin 3 - R46 1000 996
IC91 pin 5 - R61 997 1011
IC93 pin 12 - IC94 pin 4 99.2K 98.9K
This seems to suggest that the connections are ok, as are the components.
I also tested the DFS just to make sure, and that seems to be working OK.
So, the machine hangs when 8271 is fitted, and boots OK when it is removed.
The machine hangs when S2 is removed (the Econet NMI) but boots when fitted
(disabled).
When booting without the econet enabled the DFS functions as expected.
Time for another look through the circuit diagram.
Mark