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Old 18 October 2017, 16:55   #1
Signman
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Please Identify wire mod on A2000 MB

I have tried to resurrect this 2000 MB but to no avail.
With it hanging at the gray screen, many suggest it is a CIA chip problem
So I look on the back and there is this modification with a wire to the chip from the expansion Port/slot?

Take a look at pic and see if anyone can help.
Thanks
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Old 19 October 2017, 10:49   #2
Sanxion
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Hi Signman

I am in the process of doing exactly the same thing as you...I do believe my Revision 4 board has the same wire modification as in your picture but do not know what it's purpose is.
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Old 19 October 2017, 15:52   #3
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You guys should compare motherboard revisions. Could be a standard factory mod for a PCB error. Looks like a connection from the video slot, probably would not affect booting. Check the schematics and let us know exactly which two pins are connected.

Have you tried getting back to basics and removing the accelerator in the picture, all expansions and replacing the kick switcher with a single ROM?

Can you post larger pictures of the rest of the board?
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Old 19 October 2017, 15:54   #4
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Also just noticed that Varta still there! Check out other A2000 posts in this forum to deal with any battery leaks and potential corroded traces near the CPU!

Could be my eyes but looks like green on the legs (battery acid) of the CPU so almost certainly that could be a big part in you black screen.
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Old 19 October 2017, 16:21   #5
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I have been getting a light gray screen which many point to cia chips, just switched and reseated them, could scrounge up some spares.

Here are better pictures. I have pulled everything since that photo was taken, new rom, new cpu, no more rom switcher. The foam residue on memory chips is from rom switcher.

From my untechnical eyes, I can't see any damaged traces.
Yes, 4.2 revision board. wire from video slot to cia chip. There was a Video toaster in that slot.
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Old 21 October 2017, 07:24   #6
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I agree with the above poster, looks like early stages of battery corrosion going on - you need to snip that off asap or you'll end up with a repair job the size mine was. It will happily corrode the pins and contacts on the CPU slot too by the way. I managed to clean mine up so that it's working, but I plan to replace the whole slot connector just like I did the 68k socket. And the kickstart socket. And the keyboard socket, and the mouse and joystick sockets. You get the idea
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Old 21 October 2017, 15:22   #7
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The first photo is how i received board and right away snipped off battery. Some minor corrosion but I can’t see any spreading of damage.

Still after everything I have done, hangs on light gray screen.
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Old 21 November 2017, 12:32   #8
A10001986
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This mod connects pin 18 of the CIA U180 to Pin 36 of the internal video slot. This is a parallel/centronics signal (strobe), which is supposed to be there. Either it wasn't on Rev 4 boards, or the trace was damaged somehow.
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Old 23 November 2017, 05:14   #9
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This is a revision 4 board that has been “field upgraded”

I am about done with this and still looking for MB replacement. I wouldn’t care except this came with some nice upgrades, 50 mhz accel. and video toaster with megachip.
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Old 23 November 2017, 05:24   #10
dalek
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Have you tried removing the megachip and using a regular agnus? I know that if the megachip is not making proper contact you'll get a black screen. If you don't have a spare agnus at least remove the megachip and clean the contacts on the socket and megachip and try a reseat.
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Old 23 November 2017, 06:07   #11
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I did try with another agnus, same thing.
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