Date   : Sat, 06 Jun 2009 12:56:22 +0100
From   : jumbos.bazzar@... (Mark Haysman)
Subject: Issue 4 will not accept a 1770

Hi.

May have a Chip select fault then somewhere, you're going to need a spot of 
luck to diagnose that without a scope.

Mark.

----- Original Message ----- 
From: "Andy Ford" <acorn@...>
To: <bbc-micro@...>
Sent: Saturday, June 06, 2009 12:03 PM
Subject: Re: [BBC-Micro] Issue 4 will not accept a 1770


> Thanks to everyone so far for help and advice.
>
> I verified via *FX that the roms are identified (they were) , although
> as I say none of the components fail in another machine (I have two 1770
> interfaces)
>
> I had an hour this morning so I whipped the board out and tested the
> following...
>
> 1. Visual inspection on solder side of board to check all pins are
> present (all ok)
>
> 2. Checked continuity between socket side and solder side (all ok)
>
> 3. Carefully checked for continuity between each socket pin (component
> side) by following the tracks one at a time to the nearest suitable test
> point / component along the board (so at least I know the socket is
> wired ok to other components)
>
> Not sure what to try next really,  I do have something else I could use
> this machine for and have one that should arrive via Ebay in a few days
> which will become the new "home" for this kit. Just a bit unfortunate
> (typical for me) that the machine I had dedicated for this has this
> fault. Oh well. :D
>
> :)
>
> Andy.
>
>
>
>
> Mark Haysman wrote:
>>>>  I'm certain the ROM's are fine, as I have a functioning WE 1770 board
>>>> (the WE is an issue 1) in an Issue 7 B, that's the machine I
>>>> used to test the newer components in too.
>>>>
>>> Have you checked the machine is 'seeing' the ROM? Does another ROM work
>>> in that socket? I've had one iss4 machine with very dodgy ROM sockets in
>>> the past.
>>>
>>> While 1770DFS doesn't start up if it can't see it's controller, it
>>> wouldn't be too hard to write a bit of BASIC read the first few bytes
>>> from the ROM to check it is actually there.
>>>
>>> I'd also check the /CS line on the FDC  is being driven correctly (ie.
>>> the address decoding is working)  tho this really needs a scope.
>>>
>>
>> You can check a ROM is being seen by forcing it to do a language startup, 
>> if
>> the ROM is in the socket next to the OS for instance, a
>>
>> *FX142,12
>>
>> Should give a short message identifying the ROM, although it will crash 
>> the
>> machine. 13, 14 and 15 are the next ones alog.
>>
>> As for the Watford DDFSs, V1.54T is compatible with the Acorn boards (and
>> mine), and uses the DDB3 PCB, all (?) earlier versions use the DDB2 
>> board,
>> and have things located differently.
>>
>> Mark.
>>
>>
>>
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>>
>
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