Amstrad CPC464 Plus - Restoration, Repair, & 'Super Plus' Upgrade
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02-10-2022 8:16am#1
PART 1 - Monitor
A large and image heavy thread this, for a large and drawn out restoration project. The CPC Plus range were obviously guilty of failing to deliver, albeit, Amstrad never gave the range a fighting chance to begin with. Nevertheless, I'm a fan of all things Amstrad, and the CPC Plus range is no exception. I picked this up on eBay earlier in the year, complete with its original CM14 monitor...though they were only tested as far as powering on, and that's all....so a slight gamble. It arrived all packed up, safe and sound which is the first hurdle overcome!
^^ As can be seen, it's absolutely filthy, so will need a complete disassembly for deep cleaning. Onwards wit that....
^^ Monitor opened, discharged, and completely taken apart. This later got the full on bath treatment, and an intensive clean.
^^ I compiled a cap kit for the monitor chassis, these are the original caps in place. The chassis looks in relatively clean condition which was a nice surprise.
^^ Shiny new caps in place. The pcb is a nice single sided one to work on, desoldering was simple and quick.
^^ These x2 grey caps were listed in the service manual, but what it didn't mention was that they're non-polar caps, so the replacements I bought weren't suitable. Turns out the nature and values of these caps aren't particularly easy to source here in Ireland without paying significant postage costs from the US, so they'll remain in place for now. They're part of the audio circuit, so non critical. I'll replace them later on at some stage.
^^ Similarly C508 here is listed in the service manual as an electrolytic cap, but doesn't appear to be that type. I've left it in place, and will get to it down the line at some stage.
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PART 2 - CPC Disassembly and Clean
Next up is the 464 Plus itself, and as seen earlier, is thoroughly filthy. I notice on it too, that the tape eject button doesn't appear to work, in that the button presses fine, but the spring tension to lift the lid is missing causing the lid to stay closed.
^^ Eject doing nothing.
^^ Ahh, upon opening the unit I seen the spring was out of position. I popped it back into place, and will test it later on when it's back together (it worked perfectly.
^^ Absolute filth.
^^ PCB got an IPA bath, ready for working on.
^^ Disassembled, and ready for a real bath with the monitor shell.
Post edited by Inviere on1 -
Part 3 - Keyboard Disassembly and Clean
The keyboard itself was the same as everything else, filthy. So that needed a good taking apart and cleaning.
^^ Much better. There is some slight yellowing on the keycaps themselves, but nowhere near enough to warrant a retrobrite at this stage.
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Part 4 - Capacitors, again.
^^ Capacitors on the main PCB replaced.
^^ Capacitors replaced on the tape deck pcb...tape deck also given a thorough cleaning.
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Part 5 - Reassembly and Testing
So, time to put it all back together and see if it still works!
^^ Back into its shell.
^^ Well, it certainly looks so much cleaner and brighter. Does it work though?
^^ Boom, nice one, it works.
^^ My phone is making the images of the screen look a little washed out. They're more punchy in person, I just can't seem to get a decent picture of it.
^^ Finished up by giving the power & video cables a good scrub too, they were flithy.
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Part 6 - the C4CPC
Next up is something that when I seen, I knew I had to have one. It's a custom made flash cartridge for the CPC Plus range, called the C4CPC. You can get them through a gentleman called gerald over on the CPCWiki forums. It obviously allows you to play and & all CPC cart software, but it can also load games converted from disc to cart, and so on. A huge library available.
^^ The C4CPC in all its glory. I had @Steve X2 print me up a nice case for it too, which came out lovely (thanks again Steve, as always good sir!).
^^ It works an absolute charm. Instant loading of and access to any Amstrad cart software (and more).
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Part 7 - Beginning the "Super Plus" Upgrade...
The 464 Plus and the much more expensive and harder to find 6128 Plus have one thing in common, one very important thing actually, the mainboard itself. It turns out the 464 Plus and 6128 Plus are identical, with the aforementioned 464 Plus only missing the extra components that the 6128 Plus has. Luckily, all we have to do to convert the 464 Plus to 6218 Plus spec is to add those components in!
Lets start with the ram. The 464 Plus naturally has 64KB or ram, whereas the 6128 Plus has double that, totalling 128KB of ram. Lets add the missing 64KB of ram here, to bring the total on this 464 Plus up to 128KB. But first up, let's check the current 64KB of ram is all present, accounted for, and working. We can load the Arnold 5 diagnostic cart image using the C4CPC to do this...
^^ As can be seen here, banks 0-3 (x4 banks of ram) are detected, and ultimately check out fine.
^^ The pcb is wave soldered, meaning any & all through-holes are filled with solder. The tedious task of firstly desoldering the required holes. IC13 here is half done, and this is where one of the new ram chips will go.
^^ The required resistors have been added to R28 & R55.
^^ x2 DIP sockets for the ram, and some new ram chips (only x2 of them here are needed.)
^^ Sockets added, and new ram installed. That should bring us up to a total of 128KB.
Next, are the pcb components needed for the ram to work.
^^ New capacitors added to C12 & C13.
^^ That's the board with the newly added components in place, and ram upgrade complete. Will it work though?
^^ Loading up the ram test again, we see now that banks 0-7 are detected, and thankfully, all test perfectly. Noice, that's 128KB of ram.
Time to test that with some 128KB-only tech demos from the C4CPC cart...
^^ Sweet as a nut, 128KB of ram working away perfectly.
Post edited by Inviere on6 -
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Part 8 - Adding Disk Drive Functionality
This is the big one. The 6128 Plus had an internal disk drive, while the 464 Plus only had the tape deck. We can add in disk drive functionality to the 464 Plus to bring it truly in line with the 6128 Plus. There's a few ways to go about this, ultimately I wanted to preserve the original case aesthetics, so I'm choosing to use an external GoTek drive. To do that, I'll still need to add all of the required components, so let's crack on...
^^ On a 464 Plus, pressing SHIFT & ENTER is a shortcut to the tape run command. As you can see here, doing this initiates the tape loading procedure.
^^ Christmas morning for an adult!
^^ There's a LOT of wave soldered holes that need to be desoldered...
^^ I found the easiest way to do this, was to add solder onto the original solder, and then vacuum it off using a desoldering gun. You can see here the top row of IC3 I've begun to add solder.
^^ LOTS more solder blobs added
^^ IC Sockets added, and then chips installed. Note the chip down in the bottom right is still missing, slight boo boo made there, I'll show later.
^^ All resistors added and soldered into place.
^^ Network resistor needed for position NR01. They don't seem to make 7 pin versions of these anymore, so the advice was to get a 9 pin one and snip the back two legs off, which is what I done here. Don't worry, I did solder it in after this pic 😊
^^ Not sure why Amstrad fit these patch wires in, as the pcb traces go where they're supposed to go. Anyway, with the new components in place, the wires don't really fit where they were originally. So I chose to fit them back into place but on the underside of the PCB.
^^ Almost there, you can see the resistors, caps, and IC's in place now. That little chip in the bottom right though is missing still. It's a hex invertor.
^^ Here's why it was missing, the one I ordered was a different model altogether, and was SMD based. The one on the foam protector arrived later on, and that's the one needed.
^^ Balance has been restored, the missing chip is in place.
^^ Now lets try the SHIFT & ENTER shortcut again....this time, it throws an error, because the 464 Plus now thinks it's a 6128 Plus and is in disc-mode....fantastic, it's looking good, and everything seems to be working.
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Part 9 - Testing the Tape Deck
^^ The only Amstrad tape software I have, it better work!
^^ Now I've to manually switch to tape mode, with the command :TAPE.
^^ The moment of truth, will the tape deck work?
^^ Wow, delighted, it works a charm. Tape loading times though? Christ....we're so spoiled today!
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Part 10 - Keyboard Fault
Having now tested the machine a fair bit, I noticed one significant issue. The UP cursor key wasn't working normally, and required an unhealthy amount of pressure for the key to trigger. The helpful people over at the CPCWiki forums advised me the membrane is likely the issue here, and needs cleaning. So onwards with that...
^^ Keyboard back out, disassembled, and membrane exposed.
^^ Wow, look at that. It's caked in 30 years of dust and hair.
^^ Back together, and a quick check with the C4CPC and the Arnold 5 Diagnostic rom keyboard tester, the UP key was now fixed. A gentle press is all that's needed now, same as the other keys.
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Part 11 - Disc Drive Connections
There's a few ways of doing this, and like I said I didn't want to cut the case to fit a fixed connector. So I opted to use the IDE ribbon method, but one small difference was that I didn't want a long wavy IDE ribbon hanging from the back of the machine. So I chose to fit a female IDE extension cable, giving me a nice clean connection at the back, and nice and neat/unobtrusive when disconnected.
^^ The female IDE extension cable. Stripped, and prepped. The wires are pretty thin and fiddly.
^^ Wires split into the correct order, and soldering begun.
^^ Done. It could have been a little neater, but the soft/bendy strands of wire make this very fiddly. A steady hand needed, because causing a short here is easy.
^^ A small patch wire added to tell the Amstrad to use the external drive as Drive A: - without this, it defaults to Drive B and that can cause compatibility issues with some software.
^^ Next up was the route 5v for powering the GoTek.
^^ Cables routed, and case closed. Delighted with that, it looks very neat while preserving the case without any nasty holes etc.
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Nearing the end now, one last thing is to...y'know...actually see does any of this work! Time to connect the GoTek and put it all to the test..
^^ Yus! It powers on the GoTek, and the GoTek is able to browse the game images perfectly. Just need to see if the Amstrad can load anything now...
^^ Lets select a game on the GoTek...
^^ Ok....the Amstrad is able to browse the "disc" as if it were a real disc....
^^ Good god...it actually works. It's now a fully fledged 6128 Plus specced machine.
^^ Trying one of the very few Plus disc images that wasn't cart based...works perfectly.
^^ Some "Doom" homebrew...yeah, that was never going to happen on a machine like this 😊
^^ This is fun....
^^ Remember that Tape game I had above? This is the disc version. I tried it to compare loading speeds. Needless to say, the GoTek blows the cassette out of the water.
^^ Everything working perfectly.
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Part 12 - GoTek Speaker
One last thing was to add a piezo buzzer to the Gotek, so it can mimic the sound of a disc drive reading. Very easy to do, but the buzzer I ordered was WAY too big, and had to be cut down to size to fit. Not my finest work, but I really wanted to finish this project given how long it had gone on for.
Pins and connector added to buzzer wires, and then the connector simply plugs onto the appropriate GoTek pcb headers. The drive now pulses away when reading, and really gives an extra layer of authenticity to using it.
^^ Job done. Finito.
The 464 Plus is now a 6128 Plus spec machine, even eclipsing the 6128 Plus because it has cart features, disk drive features, AND tape deck features...all in the original footprint. A very enjoyable project this one, but also one I'm glad to put to bed.....for now. I say that because I'm on the waiting list for an SVI-CAS, so it'd be nice to add an external tape connector to this machine later on, to truly open it up for any & all game formats.
A huge thanks to the knowledgable folk over on the cpcwiki foums, and to Gerald for the C4CPC.
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