A500 Restoration Rusted mouse port advice

[Nekoniaow]

Originally Posted by Supamax

What's Brasso?

As usual, Wikipedia is a fluffy kitten:
http://en.wikipedia.org/wiki/Brasso

[pandy71]

Originally Posted by Zippy Zapp

I am going to try the Solder Paste technique next although it doesn't look terrible I like the idea of a bit of protection.

[ Show youtube player ]

A bit OT but can't resist - look at the "King of the Leading" !!! [ Show youtube player ]

[rikbliz]

(deleted)

[Zippy Zapp]

As an update I managed to replace the port 1 DB9. Unsoldering the pins was easy, the larger mounting clasps were not. Lots of solder and my desolder tool couldn't do the task as it was not enough power. I ended up clipping the big pins on the front side and removed half at a time. I then had to stick the solder iron on one side and use a solder sucker on the other as my wick just plane doesn't work.

Soldering new connector was fairly easy except, again, those large mounting clasps you really have to heat a while. I upped the temp too but it took a bit. In the end it came out nice. Not bad for a hack.

Powered on and working fine except the muse moves wonky on the left and right movement. Not smooth and very slow. Checked on another 500 with same disk and it is fine so is it possible CIA is going bad?

I'll upload pic of finished job later...

[Jope]

The CIA doesn't have anything to do with mouse movement.. Try swapping Paulas between the boards. If the Paula wasn't the culprit, then check the 74LS157 at U15.

Also measure continuity from the connector side of the mouse port to U15.

Mouse pin 1 -> U15 pin 2
Mouse pin 2 -> U15 pin 3
Mouse pin 3 -> U15 pin 5
Mouse pin 4 -> U15 pin 6

[Zippy Zapp]

Paula, Roger that. I'll swap it out. Come to think of it this board has corrosion on it on one of those 74 series chips. Not in front of my Amiga, at the moment, but is U15 near the CPU/Expansion connector? That chip's legs are green. I may replace it too.

The CIA is more floppy stuff, huh?

Thanks!

[Jope]

U15 is near the joystick ports, a small TTL chip.

One CIA does lots of floppy control stuff (but not the actual reading/writing, which is paula), the other does parallel port stuff. Check out the schematics for the low down.

[Toni Wilen]

I guess I need to post mouse connection correction as usual

CIA: Left mouse button (and joystick fire button)
Paula: Right (and middle) mouse button. (Joystick second/third button if available)
Denise: Movement (via U15). Both mouse and joystick port. It is practically guaranteed broken connection or damaged U15 if only joystick port or only mouse port has movement problem.

[Jope]

Originally Posted by Toni Wilen

I guess I need to post mouse connection correction as usual

CIA: Left mouse button (and joystick fire button)
Paula: Right (and middle) mouse button. (Joystick second/third button if available)
Denise: Movement (via U15). Both mouse and joystick port. It is practically guaranteed broken connection or damaged U15 if only joystick port or only mouse port has movement problem.

Argh, I forgot to correct my post after looking at the schematics. :-D

There you go.

[Zippy Zapp]

Thanks, guys for the info! Mouse buttons work fine as does vertical movement. So U15 or Denise for the wonky movement on the horizontal movement. I will check it out.

Im guessing that the U15 chip is an off the shelf variety that is still quite available today?

Don't know how to test it other than to replace it. Of course I will install a socket.

@Toni
I am betting that CIA for mouse is a common misconception, based on your reply. I have not looked at Amiga schematics since I was still in High School.

Thanks!

[Jope]

Yes, it's a regular 74 series TTL.. Definitely install a socket while you're at it. :-)

Be sure to get a 74LS157 to replace it, chips with other letters in the middle are subtly different in their behaviour, even though the basic function is the same in all 157s..

[Zippy Zapp]

Ok, Thanks Jope! Here are some pics of U15 which is corroded.

First pic is the replacement Joy1 DB9 so you can see before and after if you want. I am not a ninja soldering guy so this was really the first time i have attempted something like this. The more I learn the more I like it!

[Jope]

Since it's not a valuable custom chip, if I were replacing this, I'd just cut the pins off next to the package with a pair of small electronics cutters, then desolder the pins individually.

[Zippy Zapp]

That is exactly what I am going to do. Do you think that corrosion is the culprit? Seems to me that would make for a bad contact and "wonky" behavior... Im thinking the one right below it is going to get changed too as it has corrosion on the pins adjacent to U15. Since they seem to be inexpensive ICs, it seems prudent.

[Jope]

Unless the corrosion has eaten some traces or conducts electricity to mess up the signals, it probably is not the reason.

Nevertheless, you ought to clean it up while you're in there. :-)

[Zippy Zapp]

Good to know. Will most certainly clean it up. Just put an order in to Digi-Key as these parts are very cheap highly available still. I think I paid $0.63 per IC. The sockets were actually more because I went with machined lower profile. I bought a few other extra of the 74 chips on the MB as quite a few were green and corroded. As easy as it is to put a new one in I see no reason not too in case the corrosion causes any probs.

Whoever owned this particular A500 should be slapped. Looks like they stored it in the rain or something.

I probably should replace all the caps while I'm at it but I didnt order any so I'll hold off. I noticed two of the pins on the Denise are white corrosion while the rest are nice and shiny. Same for the socket. Ill try to clean that bit up too. Nail polishing foam block works great for this.