Date   : Wed, 16 Sep 2009 19:34:34 +0100
From   : pete@... (Pete Turnbull)
Subject: No longer Mouldy Beebs

On 16/09/2009 11:36, Mark Haysman wrote:
>> This is the chip just above the ROMs, to the right of th CPU/VIA. Mine are 
>> marked (C)Acorn and what looks like a VLi symbol? (Picture at 
>> http://i743.photobucket.com/albums/xx75/dominicbeesley/vidproc.jpg)
>>
>> No signs of heatsinks anywhere.
> 
> The VLSI chips do not require a heatsink. From the fault you describe, it 
> could also be the data bus buffer at IC14 (LS245), that can cause spurious 
> things to appear on the screen and odd crashes if it starts to play up. 
> Timing is critical on those, you can't even use an ALS245 in there, it must 
> be an LS245. As it's in a socket it's an easy thing to try first.

Actually, substituting an ALS245 is the official Acorn modification for 
timing problems when using a second processor, and I've never known an 
ALS245 to cause a problem itself.

-- 

Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York