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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: TjLaZer on December 29, 2010, 06:58:21 AM

Title: A590 memory problem after trying to mod
Post by: TjLaZer on December 29, 2010, 06:58:21 AM
Well I had a spare A590 and some time and thought I would try the power mod hack.  But at the same time I installed 2MB RAM and when I tried to power it up it did not make a sound, but made a bad smell!  Turned it off right away and the RAM chips were hot and smelly.  I'm sure they got toasted.  The mod looked fine not sure what happened.  Removed the mod and tried to see if the thing was still alive.  Well ROMs were toast so I installed a new set and it fired up.  But now I cannot get any RAM to show up. Tried some 512k RAM from my A2091.   Any ideas?
Title: Re: A590 memory problem after trying to mod
Post by: alexh on December 29, 2010, 09:56:00 AM
You've probably melted the PCB somewhere. Go over it with a magnifying glass both sides looking for a burnt track.

Perhaps you put a RAM chip in backwards and inadvertently connected +5v and GND?
Title: Re: A590 memory problem after trying to mod
Post by: TjLaZer on December 30, 2010, 01:57:05 AM
Quote from: alexh;602633
You've probably melted the PCB somewhere. Go over it with a magnifying glass both sides looking for a burnt track.

Perhaps you put a RAM chip in backwards and inadvertently connected +5v and GND?


Thanks.  I will have a look over on my board.  

I wonder if I got the wrong RAM for my A590.  Is this the correct RAM for it?

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_42315_-1
Title: Re: A590 memory problem after trying to mod
Post by: alexh on December 30, 2010, 09:24:09 AM
That is the correct RAM, 256K(bit)x4 (128Kbytes each) @ 80ns (120ns minimum required) so 16 chips should have given you 2Mbytes. I think all 256Kx4 PDIP DRAM chips have the same pinout.

Should have been fine. Did you check each one to make sure they didn't send you a rogue one?
Title: Re: A590 memory problem after trying to mod
Post by: TjLaZer on December 31, 2010, 07:22:52 AM
Quote from: alexh;602822
That is the correct RAM, 256K(bit)x4 (128Kbytes each) @ 80ns (120ns minimum required) so 16 chips should have given you 2Mbytes. I think all 256Kx4 PDIP DRAM chips have the same pinout.

Should have been fine. Did you check each one to make sure they didn't send you a rogue one?

Well I managed to get 512K working without errors, but anything beyond that I get errors and lockups!  I also noticed that some of the memory sockets melted a little bit from the heat!  Really did a number on it.  But at least it works with 512K...  I swapped over all chips from a working A2091 to see if it was one of the socketted chips.  No juice.  Not sure what else to try.
Title: Re: A590 memory problem after trying to mod
Post by: mechy on December 31, 2010, 12:21:52 PM
As alex said,thats definately the right ram,sounds like they were in backwards.If its melted/tarnished the sockets then it may be a case of the ram not making good contact that is causing errors. Do you have jp1 set right for the amount of ram?
Title: Re: A590 memory problem after trying to mod
Post by: Zac67 on January 01, 2011, 12:25:08 PM
Cheap sockets with heat damage are unreliable at best - you'll need to replace them with decent ones.
(http://www.reichelt.de/bilder//web/artikel/C130/GSP.jpg)