A500 + with leaking battery

[avinitlarge]

Ive bought a faulty A500 + from eBay, I expected the battery to have messed everything up. It arrived today and it in excellent condition, VERY slight yellowing on the keys but the case has no yellowing at all. I popped it open and, Ewww, what a mess. I normally do reballing and other SMD work but this actually looks like fun to repair. Ive cleaned most of the mess up, there were a few rotten traces near the battery which were easy to fix, Nearly all the traces under U12 are open circuit, Thats tomorrows job. I was going to use my hot air wand to remove U10 and U12 but due to the age of the motherboard, I didn't want to risk delamination, So I cut all the legs on the chips then removed the legs separately. I ordered the new chips before doing any work on the board, There were too far gone plus replacements are cheap. Hopefully it will spring into life after the trace repair and chip replacement.






Here are a few traces Ive repaired

[Zetr0]

WoW,

some nice rework there avinitlarge!

[avinitlarge]

Thank you. I actually enjoyed doing it, far more interesting than the BGA's I usually deal with

[Zetr0]

Well it shows you enjoy it, thats a lot of time in that motherboard there - and thats not just with an etching pen and de-soldering!

Having repaired a few A500+'s - I doth my hat sir - very nice work =)


U10 and U12 certainly had been leaked on - I suspect the A500+ was stored on its end for a while =)

[dlfrsilver]

yeah. U10 and U12 need to be removed, and finger crossed that you can repair and trace -patch all the vias deteriorated by the gunk :/

[spannernick]

Very nice work,well done.Love it when people show what they have done,shows how good they are at doing this sort of thing.

It was stupid putting a battery on the board,so many of them leak,shame they didn't design it so it was not near anything.Will you be putting in a coin battery in or no battery at all..?

I had that sort of battery in my Alfa Ram board for my A1200,lucky it didn't leak,I took it out and replaced it with the same type of battery(I know I should of put in a coin battery) but it's still not remembering the time even when it's found the clock.

[demolition]

Originally Posted by spannernick

It was stupid putting a battery on the board,so many of them leak,shame they didn't design it so it was not near anything.

I wouldn't call it stupid as most of these batteries did not leak for maybe 10 years. That is a very good design lifetime if you ask me. If they had specifically designed the entire Amiga for a 20 year life time, nobody would be able to afford it in the first place. Then they would also had to make sure that all the capacitors would last that time. While we know now that the non-SMT caps in Amigas are generally problem-free after 20 years, they would have had to pay a premium to get some that were guaranteed to last that time.

I remember replacing identical batteries on many PC motherboards in the 90s and they were leaking heavily even after 3-4 years so they were much worse designed. Perhaps they were over-charging it which caused the early leaking.

[avinitlarge]

Originally Posted by spannernick

Very nice work,well done.Love it when people show what they have done,shows how good they are at doing this sort of thing.

It was stupid putting a battery on the board,so many of them leak,shame they didn't design it so it was not near anything.Will you be putting in a coin battery in or no battery at all..?

I had that sort of battery in my Alfa Ram board for my A1200,lucky it didn't leak,I took it out and replaced it with the same type of battery(I know I should of put in a coin battery) but it's still not remembering the time even when it's found the clock.

I take pictures of everything I do, Its good to have something to look back on and can be useful for other people. You should see my engine build and car albums, Stupid amount of pictures.

I have a some new coin battery holders, I will be fitting one of those with a diode once I know its all working.

I repaired a 500 expansion board, Clock circuit was messed up due to a leaking battery. I repaired it all and it works fine but that won't remember the time either, I need to have another look at that at some point.

[spannernick]

This is a video of the same repair you are doing to your A500+ ..interesting.. [ Show youtube player ]

[avinitlarge]

I was watching that exact video a few days ago, Thought the repair was a little untidy but if it works, it works

[avinitlarge]

Hopefully thats it all done. Got to tidy it up a bit then fit the IC holder. Still waiting on the new chips



This looks messy but its better than what was there before. Fitted new clock components too

[spannernick]

Whats the blue stuff,is that like the solder mask,to protect the board..?

[avinitlarge]

Originally Posted by spannernick

Whats the blue stuff,is that like the solder mask,to protect the board..?

You could call it that, its nail varnish

[avinitlarge]

Ive hit a bit of an issue. Im unsure of 1 point, On U12 I am getting a short reading between pin 7 and pin 13, It looks like there is a trace between the 2 points I have circled in the picture. Problem is, Ive fitted the socket so can't actually check it. Ive looked at the schematic and can't see anything, Ive checked on a 6a motherboard and there is no short. Would anyone have a motherboard that they could possible check??

Cheers

[prowler]

There's no short circuit on my Rev.8A motherboard, nor does it look like there's a link.

[avinitlarge]

Ive just been through my pics and I think I know whats happened. On the pin hole of pin 7, it looks like there was a loose piece of copper. That has moved and joined the 2, because it is copper, it makes it look like a trace.

Thanks for checking

[Zetr0]

Thats quite a lot of work there ahead of you, I hope you are 'aving it large... err.... avingitlarge

[avinitlarge]

I had it large this afternoon and finished it all, Sorted the little error I came across too. Ive beep tested everything and it all checks out fine, there is no reason why it won't work but something in the back of my head is saying it won't work, thats just my way of thinking, Think negative and you don't get let down.
Just waiting on the new chips, U10 and U12 (74LS244N), I also decided to order U11 and U13 (74LS373N) earlier just in case. Fingers crossed

[Zetr0]

Good luck sir, and keep us posted

[kipper2k]

i posted a hi Res pic of the exposed a500+ motherboard without the chips a while back, not sure which thread now, i also posted it on a1k.org in the hardware thread

Found em... here is the small pic...




and here is supersized

BTW, yes, there IS! a fly on the motherboard lol