I stripped down the Acorn, so that I could remove the mainboard and then very carefully cleaned, with Isopropyl Alcohol, the area where the Battery had previously leaked. I might have been a little too careful, as the photos make the area look filthy, even after a good wash…
Checking over the board, with the help of a magnifying glass, has revealed a couple of obvious problems.
Firstly, Capacitor C169 looks like it’s cracked, so I’ll need to investigate replacing that component.
Secondly, there are areas of corrosion on components and IC’s. I sat with a multi-meter and started checking the corroded looking pins on the ARM processor, mostly Pins 80 down to 70, and all appear to have continuity to the tracks on the mainboard. As the socket is empty, I’m not currently too concerned that this is the source of the boot problems, but it’s worth checking whilst I’m at it. There are some other components, such as surface mount Resistors and Capacitors, that look worryingly corroded on the connections.
From the Retro-Kit page, on restoring A5000’s, similar problems to mine seem to be caused by the RTC/RAM circuit centred around IC58. I found the schematic for the mainboard and checked the connections going to IC58 for continuity the (easy) components such as Resistors. The continuity and resistance checks revealed all was generally OK in the circuit, except for the following:
- The ground side connection on the Battery appears to be bad; probably a dry joint from my previous poor soldering job.
- The Positive power ( pin 8 ) to IC58 doesn’t appear very reliable. This is an area that appears to have picked up the worst of the corrosion, so I’m not completely surprised.
So, from what I’ve seen so far, my ‘to do’ list is:
- Replace Capacitor C169.
- Remove the Rechargeable Battery and resolder, but not before:
- Checking the corrosion to Pin 8 on IC58. Possibly cleaning and/or attempting to bridge any break with some solder or jumpwire.
- Check for any further damaged components and replace.
If I’m really lucky, this may resolve all the problems. I’m not sure I’m that lucky though.
However, I’m currently working on the principle that I should fix all the obvious, visible, problems first and then dig deeper if required.