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Amstrad CPC464 Restoration

I was hoping this would be a plug-and-play, but a machine this old was always going to be a challenge. I received this unit as part of a lot with the other 6128s and have finally received a tape to test on it.

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From the outside, the item was a little dusty. That white piece, which looks like a pivot of some sort, fell out when I rotated the unit to see underneath. Never a good sign... Either way, I plugged in the unit and power it up (it happily uses the same RGB and power setup as per the 6128). To my surprise, I got straight to the main BASIC screen! To try my luck further, I loaded my demo tape and typed RUN"...

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All good so far... then I noticed that only the left spindle was spinning on the tape player. The right wasn't collecting any of the read tape... I had a hunch where it was going......... yep.

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Time to pop it open.

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Dusty... OK... I can handle that... what I can't handle is a spring (from somewhere?) magnetised to the speaker. The ad-hoc shotty taping-and-soldering was also a little bit of a surprise.

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Regardless, looking at the tape player mechanism I quickly found two dead rubber components. The band to the tape counter had perished...

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So had the rubber ring that drives the right spindle. This makes perfect sense and explains why the machine tried to consume my tape.

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Finding spares

There's a few options online for spare parts. eBay was my first choice and I have the two main belts on the way from Germany. This'll take a while. I actually really only need the band for the tape counter, but it won't hurt to replace the main drive belt also.

The second part is a concern. It's a tight ring and my initial searching has come up with zero results. Might have to head to the hobby shop today and find a car tyre or o-ring. Meanwhile, did someome say o-ring?

Drive 'wheel'

Not having much luck with o-rings, I went to my local hobby store and bought some Fleischmann HS Scale traction tyres (00544001) (actual picture here). I bought 4 in total and just layered them up on the wheel. I was a little worried about alignment as any friction would cause the tape speed to change.

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It has seemed to have worked.. but now the main drive belt is slipping. I'm going to assume it's loose and therefore not getting the required amount of traction. More waiting until the next set of spares arrives!

Drive and Counter belts

The set was ordered from eBay and arrived from the UK in good time. As expected, two belts in a bag. Much stronger and more flexible than the belts they were to replace.

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There's one screw underneath to remove and then you just slide the belt over the wheels. Make sure you not twist the belt when installing. It's not 'extremely' tight, so it's pretty easy to install.

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Read Errors

Back to testing. The tape drive started operating perfectly, so I attempted to load the cassette once more.

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Yosh! We're getting somewhere... but then...

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Read Error Codes indicate failures whilst reading from tapes. Sometimes this is a dirty head, other times the head is out of alignment. I wiped down the head with an alcohol swab and then started to attempt alignment. Not really knowing what I was doing, I hooked up the audio to 'listen' to the data and twisted the alignment screw until the audio was loudest and clearest.

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After a lot of errors, I seemed to have it stable, so I restarted the machine and tried again. It got all the way to Block 11! Then it just wouldn't continue. I hung around until I could make it say 'abba'.

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Was the tape dead? All of a sudden I had a hunch it could be the power supply... so I swapped to an old AT power supply... but it didn't seem to be able to provide enough current...

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And then I accidently plugged in 12v...

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Take your time when playing with old electronics... I've now received the dreaded Grey Screen of Death and that means any of the internal ICs could be toast. I might muck around and try and swap the socketed ones between the 6128... but otherwise... I might have just lost the battle. $%$#%#$%#%.

There's a lot of good information here on over-voltage. Seems I've cooked the lot.

Chips on the board

I'm putting this here in case I ever feel game enough to do a full board chip replacement.

Chip Purpose Quantity Status
AY-3-8912 Sound 1
AMSTRAD 40009 32K ROM; O/S and BASIC 1
74LS145P BCD-to-Decimal Decoder 1
74HC153P Dual 4-input multiplexer 4 Found, not ordered.
HD46505SP Video PPI 1
D8255AC-5 CRTC 1
74HC273P D FLIP-FLOP 1 Found, not ordered.
Z8400AB1 Z80A 4Mhz CPU 1 Found, not ordered.
74HC32P Quad 2-input OR gate 1
74HC244P Octal buffer/line driver; 3-state 1 Found, not ordered.
74HC373P 8-BIT DRIVER 1 Found, not ordered.
M3764-20RS (Or 4614?) RAM 8 Found, not ordered.
74HCU04 Hex unbuffered inverter 1
AMSTRAD 40010/40007 Gate-Array 1
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About stevenh

Trains... trains... trains... + Electronics + Japan.
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  1. The heads on the tape drive can be finicky as well, I used to spend more time trying to align them than actually using my old CPC464

    • Thanks for the heads-up! I assume there’s a screw to adjust the vertical position? I’ll look into that once the bands are in. Meanwhile, I’m surprised it actually read the header on the tape at all.


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