Restoring Amiga 500 #2, part 2

In this post I’m going to be taking a quick look at the A501 trapdoor RAM expansion and keyboard for the Amiga 500.

First the trapdoor expansion. The A501 has a large metal faraday cage around the PCB that has the top and bottom soldered on with huge blobs of solder in three places. This is a shot straight after I had removed if from the machine.

As I moved it I heard a rattle. That is concerning. This is another device that has a battery soldered onto the board, so there is a high chance that this battery has corroded badly and potentially damaged the board.

Removing the casing was surprisingly easy, soldering iron at 400°C and a solder sucking tool got most of the solder off, then heating up the joint and a gentle pry with the screwdriver opened up the joint. Repeat this for all three joins and the case pretty much fell off.

Luckily the damage didn’t look too bad.

A little bit of corrosion but it looks like the battery broke itself off before it could do too much damage. I plugged this and the keyboard in to another Amiga PCB to see if they worked.

Then I loaded a piece of diagnostics software called Amiga Test Kit to see how things were. The memory tests showed that an extra 512MB of “Slow RAM” was attached and it passed memory tests, so some success, just a bit of cleanup needed to make sure the corrosion doesn’t get any worse.

Whilst I had it loaded I tried the keyboard test, pressing every key on the keyboard. Unfortunately it looks like about 1/3rd of the keyboard is currently dead. This may be a simple fix, or it may be an entirely new keyboard membrane is needed.

In a future post I will disassemble this to find out the cause. For now I shall leave it at this and likely clean up the casing next.

Update 2020-09-19

After some further diagnosis I made the decision to no longer repair this machine. It is going to cost way too much to bring it back to a fully functioning state. So it will be stripped down for parts.

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