Date   : Fri, 05 Jun 2009 15:59:32 +0100
From   : michael.firth@... (michael.firth@...)
Subject: Issue 4 will not accept a 1770

You have removed the NMI link (I think its S9) haven't you (it doesn't mention
this in your message)?

Regards

Michael 

> -----Original Message-----
> From: 
> bbc-micro-bounces+michael.firth=bt.com@... 
> [mailto:bbc-micro-bounces+michael.firth=bt.com@...
> .uk] On Behalf Of Andy Ford
> Sent: 05 June 2009 15:51
> To: bbc-micro@...
> Subject: [BBC-Micro] Issue 4 will not accept a 1770
> 
> Hello.
> 
> Just a bit of advice really :)
> 
> I have here an Issue 4 'B. As far as I am "aware" , this has 
> always been 
> a tape only machine. However, I am unable to get a 1770 based DFS to 
> work in it. It's simply completely ignored.
> 
> To confirm a few things first.
> 
> The parts I am using (I have tried two different sets, one by 
> WE and one 
> by RetroClinic) , both kits function and are 100% ok in 
> another machine. 
> It's just this particular Issue 4 that does not seem to like 
> it for some 
> reason. As I say, all the kit parts do work in another machine.
> 
> IC86 = Fitted a link
> IC87 = Fitted a link (as an extra note I did have a spare 
> 74LS123 that I 
> tried as part of my "testing" too)
> IC79 + IC80 = Fitted 7438's (tried the ones from the WE machine too)
> 
> The other links are set as follows (have not touched them)
> 
> S18-North
> S19-East
> S20-North
> S21-2 x East/West
> S22-North
> S32-West
> S33-West
> 
> I do not have enough spares lying around to try a 8271 based 
> interface 
> at the moment (yet) although I really only want the 1770 kit to work. 
> Yes, I did fit the ROM and the module (as I say, I have two kits and 
> have tried each component in another machine and it all works 
> fine) , I 
> traced a few of the pins of IC78 and they seemed ok.
> 
> It was suggested to me to replace the 7438 on the far left 
> side ( thanks 
> Mark :) ), this I did yesterday evening (after cursing Acorn for not 
> fitting a socket here, I have done) , although it's no better (I made 
> sure the socket I fitted was fine regarding continuity etc)
> 
> Just wondered what the next sensible thing to test / replace would be 
> really. I have a multimeter but I do not have an oscilloscope so can 
> check a few things if directed. I do have a machine on its 
> way here via 
> Ebay to put this kit into but I'd rather not have this 
> machine in this 
> kind of "limbo" state if possible.
> 
> 
> Thanks :)
> 
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