Amiga 1200 left mouse button strange prob...

[arttu80]

Hi all!

I really could use little help on this one. I recently aquired A1200 Rev.2B machine with strange mouse problem. Mouse works otherwise fine, but LEFT button doesn't seem to respond in neither WB mode neither in Early Startup Menu, but still, I can enter there holding both buttons pressed. Also I can drag WB screen up and down holding left mouse button. BUT I CAN'T select icons in WB or press anything in Early Startup. Weird!

I noticed when I make really cold startup (I mean when machine is cooled down), mouse works 100%. Second launch disables left mouse button. Now, I suspect faulty caps, but which one?  I already replaced U34 (74LS166A) chip, some small caps, like E357C and E351C. Now can anyone pinpoint what really could cause this symptom?

[gertsy]

Is the button or switch stuck down? Have you tried another mouse? Another problem, more common on 500s an 2000s is that the socket pins can slip back in the socket making a bad connection. Or it could be MB as you've mentioned.

[arttu80]

I have tried other mouse, also checked connector and using multimeter verified continuity of traces to some extent.

[arttu80]

Just for the record, managed to solve this mouse problem. Reheated Paula (U3) chip with hot air station gun. First 100C for 1 minute then 30 seconds at 218C. Now my Amiga performs flawlessly!

[vince_6]

Just for the record, managed to solve this mouse problem. Reheated Paula (U3) chip with hot air station gun. First 100C for 1 minute then 30 seconds at 218C. Now my Amiga performs flawlessly!

Great news!

[arttu80]

Great news!

Oh boy. Really must do update on this one since I pulled out  my celebration hat too soon, once again...

The symptom returned pretty soon after my last post on this Amiga so I got little frustrated and slammed it back in storage. After awhile I returned and even changed CIA (U7) I/O chip, which was kind of pain for me with little experience, even managed to damage couple of traces while removing it, so repaired these with little jumper wires.  And oh yes this was reeally helpful tool

http://www.amigapcb.org/

Now, even this din't help my sticky mouse button problem. Sooo, after some headbanging came up with idea that keyboard mouse function was the culprit (you can control mouse with keyboard), because I noticed when in workbench, when left mouse button "frozed" again I pushed any key on keyboard and this would release it for a while... Hmmm.. Now I lifted pins 13 and 14 on controller chip (U13), disabling it. Problem REALLY disappeared! Now I hacked A500 keyboard controller on it, so for now it's done! Luckily Rev2B board had easy to solder keyboard pad (I used Jope's method http://eab.abime.net/showthread.php?t=20302).

Hope this set things straight if anyone have this same problem.

[mechy]

Thanks for telling us about this, i too have ran into oddities caused by just the 1200 keyboard ribbon not making good contact etc. shorted or bad membranes can also cause alot of trouble.

[Kataklysm]

Hi I had the same problem, guilty is capacitor around U12