Amstrad CPC 464 - Part 1 - Repair.

[@retronexusio]

cannot wait for part 2... excellent content as always. Thank you

[@Four_X]

Thanks bud, so glad you enjoy my content.

[@GT-oc2sl]

OMG you just headshot the fault that i probably waste my 4 months to find lol :D Thanks for informative, entertaining and high quality content.

[@Four_X]

Thanks, one of the first things I check with no images or blank screens is check for clock, because it was missing I knew where to start.

[@8bitsinthebasement]

Man, that was a great repair. Hats off on finding that flakey gate. Just as well it wasn't the gate array, those things are well hard to find. Looking forward to part two. I've never owned a 464 so never had to service a tape drive in one. I'm interested to see your take on it. Excellent video ;)

[@Four_X]

Thanks, The DataCorder is very similar to the one in the ZX Spectrum +2 and I've done them before so I'm not expecting any surprises.

[@SLRModShop]

Nice, clean, repair! It couldn't have gone any better, could it =)

[@Four_X]

Just how I like it. Ha. It just shows how one faulty logic gate can kill the whole system.

[@GadgetUK164]

Great job =D Regards hex inverter - that "hex" comes from the fact that 74 IC has 6 gates! So the NAND simply inverting here - not converting into a Hex Inverter as there's only 4 gates! More of a quad inverter =D Very similar to the fault on that first CPC I covered. They are just using that NAND to buffer (well, create higher level too) and clean up the clock btw!

[@Four_X]

Yea I don't know why I was calling it a hex inverter, watching it back now I'm like Ahrrrr. Doh. Ha. I think it because if you look at later revision boards for the Amstrad CPC 464 they do use a 7404 Hex Inverter here. What gets me is why not just use a 7404 here to begin with like later revisions. Did Alan Sugar get a good price on the 7400's or have some stock he needed to offload. Ha.

[@SLRModShop]

You have some sort of 74 series datasheet Bible?! Where did you get that?! What keyword do I need to type on my keyboard to be able to find that?! If that's not available, I think I'll make one for myself, way less convoluted than having to google them sometimes several times a day ^-^

[@Four_X]

There called the "TTL - Pocket Guide" there spanned across 3 flip books \ volumes, each book \ volume covers "Volume 1 = 7400 to 74200 Logic" "Volume 2 = 74201 to 74640 Logic" and the final "Volume 3 = 74641 to 7430640 Logic" there made by GTP LTD. Romford England. You can also get the "CMOS Pocket Guide, it's spanned across 2 flip books \ volumes.

[@madeinjapan3485]

Chuffed for you mate, nothing better than repairing something cheaply and get it functioning again had one of these in 1989. Never knew how to repair one though, can I ask we're you got your scope from and the chip u used and we're to buy em from.

[@Four_X]

I got my Scope from here. telonic.co.uk/product-category/digital-oscilloscopes/rigol-ds1000z-series-oscilloscopes/ the chip from eBay.

[@DollopussD]

Mine has an issue with the keyboard. If I press a key it gives me a few characters as well as the key I've pressed. For example, when I press "n" I get "jhn" and things like that. How do I clean and/or fix the keyboard safely and effectively?

[@Four_X]

Just take your time. There a two keyboard for the CPC 464 a pcb based keyboard or a membrane based keyboard. The pcb based keyboard is the easier to clean.

[@DollopussD]

@@Four_X is there a separate method for each?

[@Four_X]

Nothing much between them just if you have the keyboard membrane version of the keyboard take your time and handle the keyboard membrane with care, these keyboard membrane are getting old now and getting more brittle as time goes by.

[@DollopussD]

@@Four_X how would I find out which one mine is?

[@seanf12012]

I used to have one of these in the day.

[@YNGBLD80]

Mate well done on the find, Super Enthusiasm!, any chance you briefly explain the function of the timing circuit? how the signal is actually generated. I was working on something similar myself although i understood the concept of a hex inverter still don;t understand how the crystal works with the rC circuit always stumps me.

[@Four_X]

It's nothing special there just taking a Analogue signal (Sine Wave from the Crystal) and using a 7400 inverter and some passive components to create a square TTL 5v signal for the Gate Array, think of it as crude and cheap Analogue to Digital signal Converter.

[@YNGBLD80]

@@Four_X OK Sweet mate makes sense like that cheers for the reply appreciated.

[@retronexusio]

Love how you constantly swear but also beep it 😆

[@Four_X]

Ha, KZbin would have a fit if I left it in the Video.

[@carlburton8062]

My first computer. I want one again

[@Four_X]

My first was a Toshiba HX-10 MSX, I didn't use it much and moved on to the Commodore 64.

[@retronexusio]

It might be a "noob" question: but how did you colour the NAND gates in the schematic on screen?! haha

[@Four_X]

It's just a camera trick. I used M$ Paint, yes M$ Paint to colour each gate. I then just overlaped each image with the coloured gates as I went through checking the gates.

[@retronexusio]

@@Four_X Pure wizardry... I see... :)

[@kennethfitzpatrick6726]

I have repaired 3 omega's a commodore 64 but the CPU 464 is causing me grief varios screens on start up. Any advice please