Date   : Sun, 27 Jul 2008 15:03:32 +0100
From   : jumbos.bazzar@... (Mark Haysman)
Subject: BBC B+ Disc Fault

Hi.

Did it come to you in a non-working condition, or was it working one day, 
then all of a sudden stopped? The reason I ask is if it came to you broken, 
have you checked things like a bent or pushed in pin in the 34 way 
connector? Is there other track damage around the broken VR1?

If it was working and suddenly stopped,  check the EPROMs (and any other ICs 
in sockets) have not come dislodged - reseat them a few times, and if 
possible, verify the DFS rom to ensure it's not started to lose it's 
program. Apart from that, it's get the scope out time, unless anyone else 
has some suggestions. Myself, along with a few others in here I'm sure would 
repair it for you if need be.

Mark.


----- Original Message ----- 
From: "Ian Wolstenholme" <bbcmailinglist@...>
To: <bbc-micro@...>
Sent: Sunday, July 27, 2008 2:52 PM
Subject: [BBC-Micro] BBC B+ Disc Fault


I have a BBC B+ 128K, complete with the 64K daughterboard and
1770 disc interface but unfortunately, the disc interface doesn't
seem to work.

DFS will attempt to access the disc for about two seconds and then
the drive light goes out and nothing else happens, the Beeb just waits
there and doesn't come back with an error message or anything.

I checked the disc interface against the fitting instructions in the
Service Manual and all the chips and link settings are present and
correct.

The only obvious damage to the motherboard is that variable
resistor VR1, just below the speech sockets, appears to be broken
but I don't think that's related to the disc interface.

It has had a replacement PSU at some point in its life, it is date
coded 8718, well after production of the B+ ended.  I wonder if
the PSU blew and could have blown the disc interface chips?

Is there anything obvious I can try or check, such as checking
the disc chips for voltages?

Best wishes,



Ian







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