Changes
LR04 (The golden coloured ring on the right in the top picture) is used to filter supply spikes from the floppy motors getting back to the main PCB. The original part SN8D-500 is a 125µH filter rated at 2A. If you can find this part use it, if not any filter between 100µH and 150µH with a rating of 500mA or more should work fine, especially if you intend connecting a modern 3.5in floppy instead an original 3in Amstrad floppy.
NR01 is a network of 680Ohm resistors in star configuration, this part can be hard to find, but it can be also created with 6 six standard resistors
as I have done...
C21 and C23. These connects will still be required after the mod, so you will need to remove and later re-connect the bottom end of these wires to the legs of the capacitors. Take note of which wire goes to which capacitor!
Although most of the parts are concentrated around the bottom right area of the PCB, there are a few other parts hidden around the board that need to be added. R28 (Directly behind the analogue joystick port) tells the ASIC that the CPC has 128K instead of 64K. R55 (between the ASIC and first RAM IC) connects the NCAS1 signal to the new RAM. Behind the power socket, LR04 and C39 (above the 26way floppy header) are required to supply the floppy disk with power.
Althought the new ICs could be soldered directly to the PCB, I chose to use sockets to make any future modifcations or repairs easier. There is more than enough room inside the case to allow for the extra height needed for the sockets. The components can be added in any particular order, although to make testing and debugging easier, I add added only the 64K RAM components first and tested this before I continued with the floppy control components. The minimum parts required to get the extra 64K working are: R28, R55, C12, C13, IC12 and IC13. Remember that the black bridge wires must also be connected in order for the CPC to run in this state.
If you intend adding an ABBA switch to the CPC, it's a good idea to make the modifications to the external floppy connector before you solder it to the PCB. If you have borrowed the floppy power connector and leads from a PC, then you will need to remove the yellow wire from the connector and move the red wire to the position where the yellow wire was, as Amstrad (in their infinite wisedom) decided once again to steer clear of unnecessary things such as standards.
