Amstrad CPC 6128 'restoration'

1st August 2023
​Not really a full restoration as it didn't need it, it arrived in good condition, reported as working but it would at least need a recap before testing. I want this to be one of my main workhorse computers so it will need a few mods, etc.
​I put the monitor aside for the while as this would need a different inspection, so I powered the 6128 from my own power supply. This is where the trouble started!

​Looked fairly clean inside, mainly tarnished edge connectors, good clean coming up.
Had trouble powering up, intermittent, dodgy power switch, stripped, cleaned and now all good. Next issue was the CPU, if I 'tapped' the board, particularly near the CPU it would reset, it was in a single wipe socket (#HATE_THOSE). So, next job was to swap the socket.
While I was going over the board I reflowed all the external connectors and sockets. The board was fitted with Rubicon caps, which actually tested better that the proposed Nichicon replacements, so, I only changed those that were out of tolerance.
​There were a few board mods, they looked untidy but as they matched the schematic I guess they were factory mods. There were also a few partial mods, wires floating around inside, suggesting 2 things; they had brought 5V back out of the case and at some point a reset button was somewhere as these wires went straight across the Z80 reset line/gnd. I cut these off pretty much after I first opened the case as I don't like floating wires when I plan to power it up.


​Powered up ok with a 1.1A current draw but the disk drive didn't work.
May be something to do with the 'putty' that was a drive belt, drive wheels, etc. all cleaned, and new belt fitted.
​Also, serviced the whole mechanism, cleaned, lubricated, etc
Left the motherboard on power for a few hours and covered with a cloth to simulate the case being on then took a thermal image, all looked reasonable though a few IC's were running in the high 40's and low 50's, anything that ran higher than 45 received a heatsink, now everything runs lower than 40.
2nd August 2023

​Time for a keyboard clean, so, stripped and cleaned, no issues there.
I bought a GoTek to go with it, made a rough and ready case and wired it up as drive B as I wanted to leave the base unit as the original disk drive. Generally it worked well, however, I had heard (and experienced) that some software would only work from drive A. Solution needed, I have seen a few mods on the web for this but they all involve cutting tracks, bending pins, cutting wires, etc. My requirement for this was it needed to be instantly reversible without any cutting/bending!
Looking at the schematic I decided to intercept the drive select signal coming out of IC206(pin8), so I made up a daughter board to take IC206, isolate pin 8 and put it through an Exclusive OR gate with the other input from a 1/0 switch, so it would either pass it unchanged or invert it.
​I appreciate that I could have just intercepted pins 8,9,10 on the daughterboard and used a spdt switch, but, I have other plans that will need a few switching inverters, hence the 74LS86.
In other mods.... I added a 5v (protected) tap feeding a USB socket on the Cassette connector side of the case, this is for a TZXDuino unit to enable cassette file input.
​It really does need a reset switch, this will hopefully protect the power switch that had already failed.
​A reset switch was wired in series with a 100k resistor across the capacitor C135