Amiga 500 Plus questions

[Reptile]

Hi guys, well my Amiga 500 Plus arrived yesterday and all I can say is what a beautiful machine! I have never owned one before, just a vanilla 500 a 600 and some 1200s. I think the A-500 Plus is definitely my favourite, the case is nice and white I just need to peroxide the keys

Opening her up was a hard thing to do, the warranty seal was still intact after all these years! But that is what worries me, I remember reading somewhere years ago that the A-500 Plus has an onboard battery which leaks over time, due to the warranty seal being untouched I am assuming the original 1992 battery is still on the motherboard, how easy is it to remove the battery without damaging the motherboard?

Also... should the worst have already started to happen, what methods would anyone recommend in cleaning the leakage from the board?

Thankfully the machine is fully functional so fingers crossed it hasn't reached a critical stage just yet


Thanks for the help in advance,

and a very merry Christmas to all Amigans!

[PowerPie5000]

You can remove the motherboard and then de-solder the battery... or do it the quick way and snip it out with a pair of pliers

Use some pure lemon juice (not squash ) or vinegar to neutralize any battery spillage, then use a toothbrush to give it a quick scrub around the affected areas. Some people also give it another final clean with Isopropyl (rubbing alcohol).

Hope this helps and good luck!

[Zetr0]

Hiyas Reptyle

welcome to EAB =D

the A500+ with a 1MB expansion of Chip (giving 2MB CHIP) is a wonderfull machine - when married with an GVPA500 HD8+ its a true joy to have and mine was a solid trooper at R3Play event in black pool - its also got a picture in retro-gamer magazine =D

now as PowerPie is right - you need to remove the battery as soon as possible - I did a write up on AmiBay for the very reasons as to why, and what to do - I figure dumping that info here should help some =)

---
I tried to keep it from A level chemistry as much as possible so not going into full mind-numbing and tounge swallowing reaction equations.

There would be better ways to say this but this is the laymen expression, if anyone feels a better expression or more detail is require please add to or post on =D

It is a bit winded this post so jump to the end of it to catch the highlights.


Well.... if you are still here? then Lets Begin =)


Whats is in the NiCad Battery?

Rechargable battery on the A500 is the same on the A2000 - it is a NiCad (Nickle Cadmium) Accumilator.

A NiCad Battery consists of nickel oxide hydroxide, and metallic cadmium as electrodes - this is then emersed in (potassium hydroxide [KOH]) an alkaline electrolyte.


When it leaks: Reaction Time

Initially what happens is the reaction process here starts off with with the battery leak - this causes the Potassium Hydroxide to react with the air.... this over a time and room temperature will create Potassium Perxoide. Both of these chemicals react quite strongly with Copper.

Peroxide is a VERY strong oxidizer, when you have this combined with Copper (an oxidizing metal) you have a very compound problem, as you can imagine what starts off small will cresendo to a larger problem in a short space of time.

Environmental factors do play a part in this, from temperature to air humidity - all effect this copper - potassium hydroxide / peroxide reaction.

Now potasium peroxide is an inorganic compound with the molecular formula K2O2, it is also a mild alkaline to a base pending on its strength.


How do we fix it?

To neutralize an alkaline we must use an acid: of course acid will also react with Copper, infact theres very few things copper wont react with, so we need somthing safe and controllable - Acetic acid (i.e. spirit vinigar) - although this would react with copper - its relatively insignificant when compared to the peroxide base that has built up in concentrations on the PCB.

The acetic acid neutralizes the base and provides an alternative for oxidization with the peroxide being that its an organic compount. As a plus point it also breaks down the concentrated Copper Hydroxide (those blue/green fuzzy bunnies) left over from previous reactions.


But why?!?!?

Copper Hydroxide is mildly amphoteric, This is the double whammy for the copper tracks as the more that reacts the more alkaine is produced thus the more it reacts untill it runs out of oxygen/copper..

There are four driving factors for this reaction

1. The amount of potassium hydroxid that leaks
2. The amount of potassium hydroxide that reacts to form potassium peroxide
3. The air humidity
4. The temperature of the PCB and environment.

I could go on with the forming of cystal and copper dendrites and electrical impedence - but thats only going to bore the pants off every one lol


In short (for those that skipped)

1. A NiCad battery has an alkaline electrolyte.
2. Electrolyte leaks and reacts with air to form a strong oxidizer
3. Copper is an verilent Oxidizing metal
4. Electrolye is an Alkaline and will concentrate to a Base
5. Copper reacts with Oxidizer causing more Alkaline
6. Alkaline reacts with Copper and Air creating more Alkaline

Once the battery leaks its like lighting a fuse to a firework and running away.


so remove the battery - clean the mess with some lemon juice or spirit vinegar - rinse completely - allow to dry and then coat the effected area with either clear laqure or pcb spray protectorant or even clear nail varnish.

just go slowly but surely and you cannot go wrong =)

[pandy71]

Originally Posted by Zetr0

---cut here---

Great description Zetr0! THX! - as a last step i recommend clean PCB with deionized water (easy to buy - used in steam generator like iron) then use isopropyl alcohol (named quite frequently IPA ISOPROPYL ALCOHOL ISOPROPANOL and also easy to buy) to remove water from PCB.

[cosmicfrog]

and if you can take some pictures as well ..........

It really is`t hard to do, main thing is get battery out ASAP

pah A500+ and GVPA500 HD8+ mine all CBM A500+ and A590
not that I`m jeallious or anything

[8bitbubsy]

Pictures!!

While you open her up, make sure to take some nice pics of the battery area. Some people here are experts to see if the machine is in good cnodition inside or not.

[Reptile]

Hi guys I am more than happy to fulfill the picture requests, I will keep you all updated, Zetr0 I might be getting my hands on a 1Mb expansion ;-)

[Reptile]

The operation was a success! Pictures are here

Reptile