A4000 mouse problem

salaxi54

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AmiBayer
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As some of you might have noticed, i did some work on my A4000 mobo, changing the CIAs into socketed. https://www.amibay.com/showthread.php?t=14941
Now, before i even went for the task, i knew there were some problems, actually one being a mouse problem, and the other a floppy-reading problem.
So, i thought that the CIA/s was/were at fault. And while at it, instead of just replacing them, i went for the sockets.
These problems were not caused by me, i got the mobo with said condition.
After the hack was finished, i thought it was something i did wrong with the sockets, but it appears not to be the case.
First off, the floppy is working well now.
Secondly, the mouse buttons do work, both left and right. But i have no pointer movement.
I have no experience over A4000's, this is my first one!
However, after a lot of reading, i'm even more confused than when i started.. :)
Optical observation has shown the following details:
There's two SMD resistors just behind the RGB port, namely R176 and R177. The surrounding pcb area appears to be a bit dark, seemingly overheated?
Then there's two ic's, namely U975 and U976 that have some of the green goo on their contacts. They're actually real close to the battery, and i've read that they have to do with the mouse too.
Also, it is my understanding that there's some "key lock" jumper which has to do with disabling both the keyboard and the mouse functions.
My machine has no key switch on the fascia, so i guess that has nothing to do with it? No jumper on the KEY contacts.
I also read that there's some fuses located at the rear, close to the audio connectors, that have to do with mouse port voltages etc.
If you read carefully my other thread with the pics, i mention a second mobo, one i bought as busted. That one got socketed too, as it was considered a "guinea pig" before working with the first one.
I removed the CIAs from the "good one", and placed them on the "faulty" board, and it works great! So, the chips are out of the question i guess...
Needless to say, the CIAs are brand new.
So, any ideas of what i should look for?
Thanks!
 
"Then there's two ic's, namely U975 and U976 that have some of the green goo on their contacts. They're actually real close to the battery, and i've read that they have to do with the mouse too."

these are your problem m8, i had exactly the same fault with my A4000, replace those 2 and you'll be good to go:)
 
@salaxi

Juv beat me to it, If you find your RTC is not being found either then replace all three SMD chips adjacent to the battery.

TC :cool:
 
these are your problem m8, i had exactly the same fault with my A4000, replace those 2 and you'll be good to go:)

I sure hope so mate, will see what i can do about 'em! It might even be the traces around them! Thanks
 
@salaxi, believe it or not the acid collects between the IC bodies & the PCB & neutralising it is very difficult to access, I recomend removal & then repair any traces & pads before replacing with new IC's.
This will prevent your system from failing at a later date due to continued corrosion.

I was stunned at how much corrosion I found under the IC's when I repaired my A4000, even the pads between the PCB & the IC legs had been eaten away.

TC :cool:
 
@TC: Yes, i have actually gave the "lemon treatment" to the whole mobo, but it trully is difficult to reach some points, just like underneath ic's as you mentioned.
This looks to be challenging..
 
Nah it's not, If you had the patience to change the CIA's then you can do this, just take your time & go easily.

Using a similar process as before but this time instead of a dremmel use a very sharp brand new scalpel & slowly 'SAW' against the legs of the IC's right by the body & slowly & carefully you will remove the bodies leaving the IC legs solderered to the PCB pads, now carefully & gently using tweezers & a soldering iron you can remove the legs...;)

I cannot emphasis the words 'slowly', 'gently' & 'take your time' :LOL:

Best of luck & let us know how you get on.

TC ;)
 
@TC: I'll get ahold of replacements, and try that. Thanks. ΕΥΧΑΡΙΣΤΩ! :)
 
OBRIGADO to Bas, too. I forgot to check under the surrounding components on my already-leaked-when-I-received-it A3000... :banghead:
 
Just ordered a set of 74HCT166's. Let's hope it does the job! :)
 
These just came in... :)

CHIPS.jpg


So it'll be surgery real soon; just not today, for i already spent my "miggy-time" sculpting a fascia.. :LOL:
 
But they are not SMD ?????

TC :cool:

Yes! I goofed! :) That's what happens when you don't see a pic, or don't ask i guess.. Luckily, the next set will be here any day now, for i thought i'd have some spares. Those will deffinitely be the right type. (y)
Fortunately, there's plenty of other stuff to do, and patience is part of my character :D
Hmm, no wonder they looked big in the morning! lol
By the way, could anyone say for sure that they could be "adapted" if ever i attempt this? I don't mean physically, but rather electrically..
 
Electrically they would be fine mate and as a last resort doable, but it wouldn't be pretty.
Knowing you as well as I do after all this time, your goal will be to get that A4000 100% original :LOL:

Best Wishes & if you need any help or advise my PM box is always open

TC ;)
 
Thanks for the offer TC, i'll keep that in mind (y)
As about the 100% original, well, the CIA sockets have already changed the percentage.. :D
 
Alrighty, the SMD chips came in, and i went like TC said, nice n' slow.
Sharp scalpel cut the legs real easy. But then it was time to clean the area.
To my surprise, the whole area underneath the ic's was terribly corroded.
Once i cleaned with isopropyl alcohol and got the area dry, i started to clean the solder pads. And that's when all hell went loose!
Pads started peeling off the pcb. I wouldn't surrender though, and started soldering thin wire to as many spots had problems, so i could solder the chips legs to the wires. Chips in place, fired'er up, no screen!
Desoldered U976, and checked just in case the board would work with U975 only. Still black screen..
Thus, i'm thinking of acquiring another A4000 motherboard and get done with this adventure. I just hope i won't have to spend so much :(
Maybe it's wiser than trying to ship my board to someone for repairs...
 
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