Amiga 500+ mouse defect

Reynolds · 11 December 2008, 07:40

Hi all,

Recently I bought an A500, with a hope of a nice little machine to set into my collection.
I knew that the mouse doesn't works at all, but thought (and still think) that I can fix it. Checked the red service reference card about the basic clues to find the cause, but I had no luck yet, as I've checked U3 (Paula), U4 Denise, U7 8520, U15 74LS157, but I hadn't find the last piece, a resistor with 5.1 Ohm inposition marked EMI1401.
On the other hand I removed the battery and inserted a socket for the new one. Near to that part I found a strange shortcut. Pictures attached. Sorry for the quality, but I have camera only in my mobile.

The chips are in sockets, except the U15, which is soldered to the mobo. Thinking to "refresh" it's connections. Others have been reseated to ensure the better connection on the legs.

Any suggestions, where to start?

Thx,
Reynolds

TheCorfiot · 11 December 2008, 12:10

@reynolds

Regarding the mouse issue, The +5V supply to the mouse on both ports is protected by a fuseable, it is a very common failure due to people plugging things in whilst the system is powered up.

You need a multimeter set to continuity & check if the "green" coloured fuseable is open circuit. If it is simply solder a suitable replacement on top of the old. I don't recomend shorting it long term but for testing purposes you can try just be carefull & ensure the mouse is already plugged in.

Regarding your photos I can't really make anything out sorry.

TC

chiark · 11 December 2008, 12:14

There's very, very, very good instructions on fixing the mouse port on Antony Hoffman's site:
http://amiga.serveftp.net/JumpyMouse.html

That's aimed at the 4k, but it explains the operation enough to be applicable to other machines too.

It might be just the fuse, as TC says - fingers crossed!

That "strange shortcut" is on my A500+ too... See my gallery for pics!

chiark · 11 December 2008, 12:16

Picture that shows same short:

(before cleanup and battery removal!)

TheCorfiot · 11 December 2008, 12:35

@all

Maybe I've been extremly lucky, but it's always been the fuseable & often down to the fact that people plug the mice in when the system is powered up.

TC

Paul_s · 12 December 2008, 22:15

Quote:

Originally Posted by TheCorfiot

@all

Maybe I've been extremly lucky, but it's always been the fuseable & often down to the fact that people plug the mice in when the system is powered up.

TC

Plugging/unplugging when the Amiga is powered on should be a criminal offence in my book. Naughty naughty people! rahhhh

Hope you get her fixed chap

11 December 2008, 07:40	#1
Reynolds Alien Breeder Join Date: Dec 2007 Location: Szigetszentmiklos / Hungary Age: 46 Posts: 1,112	Amiga 500+ mouse defect Hi all, Recently I bought an A500, with a hope of a nice little machine to set into my collection. I knew that the mouse doesn't works at all, but thought (and still think) that I can fix it. Checked the red service reference card about the basic clues to find the cause, but I had no luck yet, as I've checked U3 (Paula), U4 Denise, U7 8520, U15 74LS157, but I hadn't find the last piece, a resistor with 5.1 Ohm inposition marked EMI1401. On the other hand I removed the battery and inserted a socket for the new one. Near to that part I found a strange shortcut. Pictures attached. Sorry for the quality, but I have camera only in my mobile. The chips are in sockets, except the U15, which is soldered to the mobo. Thinking to "refresh" it's connections. Others have been reseated to ensure the better connection on the legs. Any suggestions, where to start? Thx, Reynolds Last edited by Reynolds; 21 November 2022 at 08:41.

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11 December 2008, 12:10	#2
TheCorfiot Amibay Senior Staff Join Date: Feb 2008 Location: Cardiff / Wales Posts: 1,302	@reynolds Regarding the mouse issue, The +5V supply to the mouse on both ports is protected by a fuseable, it is a very common failure due to people plugging things in whilst the system is powered up. You need a multimeter set to continuity & check if the "green" coloured fuseable is open circuit. If it is simply solder a suitable replacement on top of the old. I don't recomend shorting it long term but for testing purposes you can try just be carefull & ensure the mouse is already plugged in. Regarding your photos I can't really make anything out sorry. TC

11 December 2008, 12:14	#3
chiark Needs a life Join Date: Jan 2008 Location: England Posts: 1,707	There's very, very, very good instructions on fixing the mouse port on Antony Hoffman's site: http://amiga.serveftp.net/JumpyMouse.html That's aimed at the 4k, but it explains the operation enough to be applicable to other machines too. It might be just the fuse, as TC says - fingers crossed! That "strange shortcut" is on my A500+ too... See my gallery for pics!

11 December 2008, 12:16	#4
chiark Needs a life Join Date: Jan 2008 Location: England Posts: 1,707	Picture that shows same short: (before cleanup and battery removal!)

11 December 2008, 12:35	#5
TheCorfiot Amibay Senior Staff Join Date: Feb 2008 Location: Cardiff / Wales Posts: 1,302	@all Maybe I've been extremly lucky, but it's always been the fuseable & often down to the fact that people plug the mice in when the system is powered up. TC

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