Repair
Just before I was about to throw the CPC464 into the recycling pile while cleaning up our hobby room, I fortunately turned it on once more (for the last time, I assumed), and the startup message flickered briefly across the screen again before it went back to black. This motivated me enough to open the device's case and take a look inside. I then discovered that it even had a Vortex memory expansion card with 512 kB of additional RAM!
While trying to remove and reinsert all the ICs -- a simple method for at least partially cleaning corroded contacts -- the heatsink of the gate array came loose. This was a good opportunity to replace the remnants of the old, sticky, chewing-gum-like cooling paste with a dab of modern, silver-based paste.
After much pushing and tugging, the startup message occasionally appeared again -- a clear indication of a loose connection. To this day, I don't know exactly where the unreliable connection is (possibly somewhere in the ribbon cable connecting the old CPU socket to the memory expansion board), but at least the computer now boots fairly reliably.
During another attempt to get the gate array out of the socket (why again was I trying to do this?!), I unfortunately managed to cause the stubborn IC to do a somersault, leaving two broken pins behind in its socket. Fortunately, this was remedied by inserting the damaged IC into another socket, which contained short pieces of wire to replace the missing pins. After soldering the wires to the remnants of the broken pins, the system worked flawlessly again.
After inserting the gate array/makeshift socket combo into the actual socket on the SP512 board, the construction unfortunately turned out to sport a slightly too high profile, so that it now hits the keyboard board from below and puts mechanical stress on the case when screwing it shut. Let's see how long this lasts...
Speaking of the Keyboard
Further transport damage manifested itself in a few permanently depressed keys in the cursor block. After unscrewing the keyboard's circuit board, it became apparent that only a few of the "rubber caps," whose graphite-coated undersides close the contact on the board when a key is pressed, were permanently dented – but this was easily repaired.
Reset Button
The CPC464's power button is notorious for not being particularly well-equipped to withstand the mechanical stress of thousands of switching operations and eventually failing to function. To prevent this, installing a reset button is recommended and described in detail in the CPC Wiki. However, I chose a different location for tapping the GND level than suggested (namely, the corresponding line on the CPU socket), since the GND point suggested in the Wiki is located below the memory expansion card.
The computer's case already had a hole that seemed appropriately placed for the reset button (to the right of the video output) -- however, recesses had to be cut into the two plastic strips flanking the hole to make room for the somewhat overly thick button.
Final Touches
The computer's case was originally adorned with several toggle switches and a lock switch, which, however, were not connected internally or no longer served a function due to the lack of a key, respectively. The toggle switches were removed, and the lock switch was removed from the power supply wiring.
To cover the remaining holes after their removal, pieces of paper of a suitable shape and size were printed in (approximately) Amstrad gray and attached to the case from the inside (lock switch, to the right of the cassette drive) or the outside (toggle switches, above the keyboard). In the latter case, an attempt was made to reproduce the look of the original badge that would normally have been present in this location.
