Date   : Sun, 01 Oct 2006 18:59:39 +0100
From   : Mike Tomlinson <mike@...>
Subject: Re: One more BBC B to fix

In article <1ff6e36e4e%mjfoot@...>, Michael Foot
<mjfoot@...> writes

>Do you think the fault is caused by a video circuit problem? Do you think it's 
>more likely to be IC related, connection related or some other component?

It's hard to tell, really.  The symptoms you describe seem to be video
or memory related, but you say the machine will boot properly on the odd
occasion before locking up.  Intermittent faults like this can be a
bear.

Have you scoped or metered the 5v power connections?  Can you try
another power supply?

Leave the machine on for a while, then feel each of the RAM chips with
the back of a finger to see if one or more is noticeably warmer than the
others.

Try putting the user 6522 in the system 6522 socket, leaving the user
one empty.

Try swapping the 6502 from a known working machine.

On pre-issue 7 boards, it's very important to make sure all 6 5V/0V
power connectors are attached and are clean and tight.

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