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Old 09 November 2010, 07:28   #1
hoptoit
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Almost got it, but now a sticky mouse on A500?

Anybody having some input on this would be greatly appreciated. I've nearly completed updating and restoring our A500 to full operation. I did a Chip RAM upgrade by adding x4 DIP sockets and chips, modified JP2 and JP7A, replaced the floppy drive.

But I'm noticing an occasional glitch with the mouse sometimes. Every so often it will hang in place on the screen when I'm trying to move the cursor, usually when moving down or to the right. It seems to be momentary, then corrects itself. But it is very noticeable playing Marble Madness, as the marble goes off in the wrong direction suddenly.

I tested the phenomenon happening on both ports, and with 2 different mice - one optical and one ball driven. It's hard to tell if this is occurring with the joystick very much.

Capacitors wearing out? Did the memory modification interfere with something? I ran a few memtests and the new memory showed no errors. This isn't the worst, but any ideas?
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Old 09 November 2010, 08:47   #2
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My A2000 had similar issues I found that the DB9 connector had snapped on a few pins where they bend before going into the board, that would be where I would look first.
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Old 17 November 2010, 21:38   #3
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Quote:
Originally Posted by Loedown View Post
My A2000 had similar issues I found that the DB9 connector had snapped on a few pins where they bend before going into the board, that would be where I would look first.
I couldn't see any thing wrong where the DB9 connectors meet the board, and besides, I don't think a bad connector would exhibit the same problem on both ports.

I got this advice from over at amiga.org, to replace some of the minor mainboard chips. Does it sound like a likely answer?

Quote:
Next logical step is to replace EMI400 and EMI401, but I'm pretty sure the problem is U15 (74LS157).
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Old 17 November 2010, 21:59   #4
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U15 is what I'd swap first.
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Old 18 November 2010, 10:46   #5
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Where would you get a replacement U15 from?
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Old 18 November 2010, 10:50   #6
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Where would you get a replacement U15 from?
Farnell, RS Online or your choice of electronic service agent.
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Old 24 November 2010, 01:10   #7
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There are a few online sources which have the U15 chip for .50 cents, so no big deal there.

The only real trouble is that I've already handed off the machine to my brother and his kids:


My brother is pretty handy, so I'll ask him to work on the machine sometime. But at the moment these rugrats didn't really wanna wait around for more repairs.
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