A500+ cleanup and keyboard repair (Part 1)

Updated: Mar 14, 2021

I've been a bit delayed in getting this post together as I've been waiting for deliveries!


I felt that it was time to start working on the 500+ and getting it up and running properly. I want to run a few tests to see what issues I have, then get it all stripped down and cleaned before I get stuck into the repairs.



The disk drive clearly wasn't working. Although the Amiga turned on and displayed the kickstart screen, I wasn't getting that familiar 'ticking' from the disk drive that I remembered. I figured that swapping the floppy drive with the Gotek from my A600 would be a good way to test the rest of the machine.


With the Gotek installed, games were loading, but I wasn't able to reset the 500+ using the Amiga, Ctrl, Amiga keyboard command, I hoped that this was just down to a fault with the keyboard and nothing more sinister than that.



After some reading online, I found Amiga Test Kit (https://github.com/keirf/Amiga-Stuff) which provides a number of helpful utilities to test your Amiga. I downloaded the ADF file and loaded it onto the Gotek (see previous post if you need more info about this process https://bit.ly/3rKrpI1), booted it up and started the keyboard test.


The keyboard test registers each keypress so that you can very clearly see which keys are working and which aren't.



As you can see, all the keys were working except for Ctrl, L Shift, L Alt and L Amiga. I have to say this was a relief. It made me think that they were probably connected and a single repair would fix all 4 of the keys, also given that it was the Ctrl and Amiga keys that were faulty, I'm hopeful that once these are repaired the Amiga will reset as it should.


I did some more research online and found that the keyboard works by connecting contacts on a thin keyboard membrane and that it was common for traces on the membrane to become faulty over time. I also found this handy schematic (https://i.imgur.com/KxI1hh8.jpg) which makes it loads easier to follow the traces to work out where the issue is.



As you can see from the schematic, the four faulty keys are all connected together. The black trace runs from Ctrl, through the other three contact pads before connecting up with the right Amiga, Alt and Shift keys. I got to work and dismantled the keyboard. First thing is to remove the several hundred screws from the back of the keyboard. Once these are out the front of the keyboard lifts right off, revealing the keyboard membrane. I then used my multimeter to check some continuity. Straight away I was able to establish that the four faulty keys were all connected correctly, however, there was a definite break in continuity between the left and right Amiga keys.


In order to try and identify were the break was I scraped away the covering on the trace in a couple of places and continued probing with the multimeter. Unfortunately, it seemed like quite a large section of the trace was not working. I, therefore, decided that I would add a copper strip as a new trace and connect it directly between the left and right Amiga key pads. To do this I had to make some purchases.


I took to Amazon and bought some copper foil tape and conductive paint. It was recommended to use silver conductive paint, which is what I bought first, however, this didn't work for me at all. So I requested a refund and bought this carbon paint instead. while you are on Amazon, I STRONGLY recommend that you buy yourself a keycap puller (you will see why in a min!).


While waiting for my Amazon deliveries I decided to remove all the keycaps and clean everything up. I read a few different methods online to remove the keys but I won't repeat them here. What I learned was that the keycaps have to be pulled perfectly vertically, any lateral force can cause the plungers below the keys to crack or outright break. The best way to remove the keycaps is with a keycap puller and for £5.99 I can't believe I was daft enough to try any other way!



Whilst removing the keys I managed to completely break three plungers and cracked five more. Following a post on a couple of the Amiga Facebook groups, I was incredibly lucky to have a couple of people reach out to offer me replacement parts. Firstly Karl from Retro 32 (https://www.retro32.com/) reached out and offered some 3D printed replacements. These are still in development, but I expect that he will have them finalised soon and available on his website. I also had another member reach out and offer me some spare original parts which was incredibly generous!



It is also worth noting that the larger keys also have a metal support bar that helps the key to depress evenly, regardless of where it is pressed.


Below the keycaps were small springs, I carefully collected these together and cleaned any dust and debris that had caught within the springs.


With the keycaps removed I cleaned them up with some warm water, a toothbrush and far more patience than I normally have! I also gave the rest of the keyboard and the Amiga case a good clean, using some household cleaner and cotton buds to get in between all the fins.



Once the amazon delivery had arrived I started my repair on the keyboard membrane. I had read that some tapes can cause further damage to the membrane, so I tried to keep things as gentle as possible. I laid a piece of low tack painters masking tape onto the membrane where I wanted to place the new trace. On top of this, I stuck a length of the copper foil tape. I cut it lengthways so that it was a thinner strip and wouldn't interfere with the other nearby pads.


At each end of the copper tape, I used the conductive paint to connect the tape to the R Amiga and L Amiga pads. Once the paint was dry, I checked continuity and got a reading. It wasn't as strong as I had hoped, but I expect it will be good enough.


I plugged the membrane back into the mainboard and booted it back up into Amiga Test Kit. Using one of the plungers I shorted across the pads to check to see if the keys worked. Straight away the Ctrl, L Shift and L Alt were working. However, the L Amiga key was still faulty. This means that the trace for the other pad must be broken too.


Unfortunately, this is as far as I have managed to get so far. I will continue this in a second part, where I will attempt to repair the send trace and get everything back together and retested.


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