On Jun 05, 2016 07:09pm, Dave Drum wrote to Mark Lewis:   
      
   Dave,   
      
   I don't know if this will fix it but I have access to a couple of broken C64s   
   that may fit the bill.   
      
   Allen   
      
   ---   
      
   This text file describes what to do in order to fix Amiga 500(if one   
   of the CIA's is dead) with the parts taken from broken Commodore 64.   
      
   I SHALL STATE THAT THIS IS A HACK, ITS A HACK! ITS A HACK!!! HOWEVER   
   CONFIRMED, IT WORKS FOR ME.   
      
   ---   
      
   OPERATION:   
      
   So lets start. If your Amiga 500 has one of the two CIA's dead then you   
   can fix it for OS use and some rare NDOS games/demos. There are two such   
   chips(8520A), one labelled ODD CIA (A) at U7 and the second one EVEN CIA   
   (B) at U8, they are both socketed. The simpliest method to check which   
   one is dead, if Miggy does not start at all, is to remove the B one and   
   power it on. If it does start and shows up the so famous floppy screen,   
   then its obvious B died. But if it does not display anything then you put   
   B in place of A and try again, and if it does start then you leave it   
   there and go to strip the replacement chip from broken Commodore 64.   
      
   Note, if swapping chips does not work then you can stop doing anything   
   further as this may not be CIA's fault or (not likely to happen) both of   
   them are dead - and if so then you may skip as there is a need for at   
   least one 8520A!   
      
   In C 64 there are also two CIA's and they are at (locations according to   
   new pcb) U1 and U2 they have printed 6526B on them. So now you just need   
   to desolder one of them or both, clean up the pins and put in your Amiga   
   in place of B one. The pinouts are same so nothing can go wrong.   
      
   There are several mothods to strip the chip from pcb. I used ordinary   
   soldering iron and the simple sucking device to pick the tin. If you got   
   no such tools then you may use simple handy gas burner directly on the   
   pins from some distance. But before doing this set the nozzle not to cut   
   but to distribute the heat smoothly. Then try to toggle the burner form   
   one side to another and if you notice tin melting grab the ic - be   
   cautious its hot! Also, dont heat the chip too long!   
      
   ---   
      
   DOWNSIDES:   
      
   You can only use 6526B in place of EVEN CIA (B), why? I dont actually   
   know why doesnt Amiga boot when put in ODD CIA (A) as i have no plans   
   of these chips to see what are the differences between them. I however   
   suspect that this might be something with the registers or timers but   
   that is my own opinion, so dont take it as a real issue. Some day i try   
   to fiddle with some system monitor and peek-poke to see what is   
   different from under the OS.   
      
   As you read at the begining some NDOS games/demos might not work,   
   especially the ones who bang the CIA's directly or do some trickery   
   around them.   
      
   ---   
      
   OTHER IDEAS:   
      
   If you dare you can check if 8520A will work in Commodore 64 :) -   
   unfortunately, i wasnt able to check that since my C 64 has burnt   
   memory. I recommend to solder the socket first.   
      
   ---   
   megacz@usa.com   
      
   /\llen   
      
   ... Like Sand Through The Hourglass... These Are The Days Of Our Lives   
    * Origin: Derby City LiveWire - Louisville, KY - livewirebbs.dy (1:2320/100)