Changes

Other than the obvious tools required such as a soldering iron , cutters and a screw driver, there are quite a few components you'll need to source. Some of these are standard components that are still readily available and cheap to acquire, others such as the SED9420 Data Separator, the µPD765 Floppy Controller and the RAM ICs may prove more difficult to find.

listed as 1.5Ohm in the Service Manual Parts List, in reality it's a 1. 5K resistor.  The part numbers above correspond to the labels on the PCB, the Service Manual adds 100to all part numbers (ie: R8 on PCB is R108 in the Parts List). 

 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 ratedat 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, especiallyif you intend connecting a modern 3.5in floppy instead an original 3in Amstrad floppy. 

you'll need to do is remove all this solder. You can do this using de-soldering gauss or a pump, depending on your preference. Don't use a drill!Drilling will damage the via connections inside these holes! In most cases you can apply a decent amount of heat to remove the solder, howeverbe careful when preparing the holes for the 41464 RAM IC's as they are very close to the original 64K ICs and too much heat in this area could damage the original RAM ICs. C4 and R55 are also directly connected to the ASIC, so care should be taken when soldering these parts alsotoo.

You will also notice that there are also two black bridge wires running from the top of the PCB down to two of the holes you need to use forC21 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 ofthe capacitors. Take note of which wire goes to which capacitor!

Although most of the parts are concentrated around the bottom left 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.

== Adding the new The New Parts ==

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 morethan 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 tomake testing and debugging easier, I add 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 connectedin 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 thePCB. 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 wireto 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.

If you have chosen to add the external floppy connector, you willneed to cut the additional hole in the casing, but no other case modifications are required.