Date   : Sun, 01 Oct 2006 09:54:48 +0100
From   : "Robin Commander" <robincommander@...>
Subject: Re: One more BBC B to fix

A long shot, but have you tried swapping out the 6522 VIA chips ?

A long time ago I had an issue 7 BBC Micro which wouldn't start up (just got
a long bleep and blank screen), iirc there were two 6522's on the board and
I was able to get it to boot by swapping the chips over.

These chips have timer functionality which is potentially used in a lot of
places so they're fairly fundamental.

HTH

Regards,
Robin


-----Original Message-----
From: Majordomo List Manager [mailto:majordomo@...] On Behalf Of
Michael Foot
Sent: 01 October 2006 09:07
To: bbc-micro@...
Subject: Re: [BBC-Micro] One more BBC B to fix

Hi,

In message <$c58DJAT2qHFFwxe@...>
          Mike Tomlinson <mike@...> wrote:

> In article <6ef7606e4e%mjfoot@...>, Michael Foot
> <mjfoot@...> writes
> 
> >I've got an Issue 4 Model B here which won't start up. The best I can get
it to 
> >work is in 16k mode (jumper 26 south). In this setup, most of the time
when 
> >switched on a random configuration will occur. Usually the RGB output is 
> >completely white and the Caps LED comes on then goes off. Usually, but
not 
> >always, I can press Ctrl-Break after this and different LEDs will light
up and 
> >sometimes the RGB output goes black. Also, on only a small number of
occassions 
> >the machine will boot to a prompt but then lock up a few seconds later.
> 
> Have you swapped out the VIDPROC and ic14 (74LS245)?  If the VIDPROC is
> the Ferranti one, does it have the heatsink?

Yes I have since they are both socketed. The current VIDPROC is a VTI one so
I assume in the past the original VIDPROC was replaced with the current one.

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?

Thanks,

Mike.

-- 
Michael Foot <mjfoot(at)paradise(dot)net(dot)nz> *
http://homepages.paradise.net.nz/mjfoot/
* Replace letters between () with @ and . when replying


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