Floppy Disk Controller Repair and Diagnostics ROM for the Amstrad CPC 

You can download the Amstrad Diagnostics ROM project here github.com/llopis/amstrad-diagnostics For questions or if you're interested in contributing, join us in the Discord server: discord.gg/ETcCh6J

This is why your channel has grown so quickly, absolutely fantastic work.

Those close-up shots showing the Z80, 8255, and TTL chips bring a lot of memories :) I used to design stuff based on those all the time back in the 80s. Heck, at some point I could read hex z80 code!

This whole video was absolutely killer. Bit of troubleshooting, development and a successful repair. Best retro channel on RU-vid, hands down.

retro development vids are always welcome

Very cool =D Lovely work on the diagnostic ROM!!!

Yet another riveting detective story. No bad IC goes unpunished with Noel on the case. Not only was the repair interesting, this diagnostic you've made already exceeds anything out there for the CPC if I understand you properly. I predict this will be a tremendous asset to the Amstrad CPC community, as you yourself are. Brilliant. It's too bad Amstrad did not make much of an appearance here in Canada. They seem like fine machines. Around here, it was mostly Commodore followed by Apple II, with Atari, TRS-80, and TI99 bringing up the rear. I would have loved one of those CPC machines.

Ha! I love how you evolved the RAM test number outputting code to that easier to visualise version.

Fascinating video! I bought a 6128 in 1985, and used it for 8 years, until I bought a Mac IIci in 93. I still have both, as well as one of the DEC Pro/350 I learnt PDP-11 assembler on in 1988 as a CS student. I had the 6128 powered up maybe 15+ years ago, it worked then, except the rubber band of the floppy drive. I guess the next time I visit my mother, I will dig up all the machines from the basement and see how they are doing. This video was very inspiring!

The wonders of the Z80 CPU. That's why I still program on a ZX81 and ZX Spectrum. I would love to see more of your programing adventures, Noel.

Outstanding! Educating and entertaining us with bonus making available valuable tools - one of the best amstrad related channels!

Brilliant video and repair. Seeing that pcb and those chips brought me back to my first job on the test floor of a semiconductor assembly plant where we tested thousands of Z80s, 765s and 8255s along with 8251s, 8257s 8035s, 8085s and static ram! In any slack time I made cpu boards for projects. Great times. Great channel.

Wow, what a video. That was excellent. Thanks so much for the diagnostics ROM.

I have no experience (or Nostalgia) with this machine, but I really enjoyed this video. I know it took you longer than you expected, but the internet needs more articles and videos like this.

Neatly done! Your approach shows not only good ICO (Input/Conversion/Output) troubleshooting, but a sound knowledge of how the Amstrad platform works at the component level. Your diagnostics will likely catch on with other Amstrad users and technicians.

Ingenious -- taking a partially-working computer and using the stuff on it that *does* work to help you diagnose its own ROMs. I'd have gotten the "must remove the ROM chip so I can read it directly" business stuck in my head, and it never would've occurred to me to write a program to check the ROM's CRC. Such an elegant solution for that! I love it!

Nice one Noel. You are so knowledgeable on Z80 programming and yet, you don't look old enough!

My Amstrad fails from time to time loading from the disk. I don't think I'll have to change any chip but now I know where to look at and clean thoroughly. Many thanks.

Very cool!! Even 3 years after!

I don't own an Amstrad CPC, but I have several ZX Spectrums and I know how useful these diagnostic software are. I use DiagROM from Retroleum and of course the ZX Diagnostics you mentioned. I am sure your diagnostic software will be a huge hit and very much appreciated in the Amstrad community. Great work!

Great work and thank you for sharing your workflow of how to test a system. Also nice that you got around to working on your diagnostic code. Can't wait to see how you have progressed on it and the new features that the you and the community have added to it.

Oh wow, this was a fun little adventure! Got some assembly fun in there too. Nice!

I do not have a Amstrad CPC nor have I ever had one. But loved watching this video to see how you progress through the fault finding route and end up writing some code to help Diagnose Rom faults. I do however have a Zx Spectrum +3 with a Disk error it can not find track 0. 👍

Very interesting. I have a CO664 with that problem. Just now I know how to fix it! Thanks and happy new year from Benicasim!

I love your thought process!!!

Great work as always, Noel. Your channel is truly awesome. 😊

Nice video, I wrote about it 3 days ago. Now I must take time to see the Amstrad PPC videos and write about it too. Thanks.

Good stuff Noel. Well done. Love the development of your own diagnostics. Superb.

I absolutely loved this video, can't wait to see more!!

Bravo!!! Una maravilla, Doctor Noel.

It's always nice to look at the work of a perfectionist. Excellent work organization and clear comments. This is very motivating. Thanks to your videos, I have repaired a cassette audio player and a vintage audio amplifier. Thank you very much and good health!

Hi Noel. Nice troubleshooting and fascinating video. Thanks.

Awesome video, repair and, especially, diagnostics tool. Thanks for putting it on github. Will definitely try it out.

This is my favorite repair video, great job!

I love snooping in code! This is a great way to learn how things work. Thanks for allowing us access to view it! Great job attempting to fix this Amstrad! :D

Great video, its amazing with the older computes you really had to know assembler to accomplish useful things. I would like to see more of your assembly projects.

Great work!

Excellent video Noel and brilliant diagnostics, i'll test them on my Dandanator soon !

Superb effort! Was great to watch this unfold and lead to a fix.

Great Video , Enjoyed the way you made that daignostic tools.

I've recently started learning z80 assembly in preparation to getting a Spectrum Next, some development along with the diagnostic analsys was pure joy, excellent work! I will be checking out your code. :)

Excellent video. You are truly talented!

Thank you very much Noel for this interesting video. Not only have you found the suspect IC's but to do assembly code to diagnose future repairs and to give it to people to use means so much to us. I haven't had a single problem with my 6128's but it's now available if i need it.

Really really cool video, especially the mix between repairs and assembly knowledge.

Very informative and fun to watch, Thanks Noel :)

nice video and nice, that you are doing that diagnose software to help on repair their cpc system :)

Amazing the ad hoc rom CRC checker!!! First class Noel!

Hi Noel, when you tested that 74HC240 in the EPROM programmer, and it reported all the gates failing, it occurred to me that it actually only takes one bad connection to render the whole IC dead: if either the Gnd or the Vcc pin should fail, the rest could theoretically be fine, but there's no way of knowing that. 😉 Anyway, I was really intrigued through the whole process of troubleshooting, and - unsurprisingly! - you managed to sort out all the problems in your usual style; that is to say, with flying colours. 😁 Also good work on that diagnostics program, it is a very clever use of the Z80's OUT instructions to get those numbers on the screen in the (artificially enlarged) border area, I must say. 👍👏 It really shows how amazing Assembly programming can be, doesn't it? Oh and finally, there's something I've been meaning to say to you for a long time... do you remember when you posted your video about repairing the ZX Spectrum 128K "Toastrack"? We exchanged a few comments on that video, and you mentioned something about the lack of a menu system on the Spanish version. Well you can have those menus if you replace the ROM with that of a grey +2*; since the hardware architecture is viretually the same on the Toastrack and the +2, the +2 ROMS will also work in the Toastrack. Thus, you could even have a French Toastrack, if you wanted! 😄 All the ROM files are available on Paul Farrow's great site, www.fruitcake.plus.com/ *Unfortunately, this means the loss of the Editor program that is present in the Spanish version of the Toastrack, but such is life: you win some, and you lose some.

Wow thanks for writing this diagnostics tool Noel, I too always wondered why there was no Amstrad equivalent of ZX Spectrum Diagnostics!

Really good with the programming part. Great video.

Excelente trabajo. Un video muy interesante. Muchas gracias!!!

Amazing how you created a diags ROM !!!. You are the best, mate :-)

This is really awesome. This now should’ve kicked my ass to finally debug my 6128 and maybe do something with that bare 6128plus board that are still waiting on the shelve to get resurrected. Great stuff Noel!

Hoping I enjoyed the software part? YES! That was awesome and thanks for sharing it.

Nice work, that was a tricky one. Hope your mem test catches on.

Great job

Great Noel....eres muy grande..felicidades

It is impressive as usual, you combine hardware knowledge plus programming background without losing your expression 'mmm, interesting' in front of death screens. You demonstrates that a computer is an easy to repair device, always if you have an spare chip or whatever you might need, sometimes very difficult to obtain. Go ahead about diagnostics tool for Amstrad, I am sure you'll offer us a professional solution, for sure. I read comments and I don't see many Spanish followers, don't understand, you offer a really professional work, thanks.

More retro programming video would be good to watch. I like watching the process of how you repair things :)

When diagnostic software hangs, my thoughts was exactly the same - something wrong with CS and there is bus conflicts.. 😂 Great repair! For diagnostic software update, You can add 8255 response test (writing registers with initialization values one by one and then reading back) and for floppy controller and then verifying values.. Main rule - don't read back same register after just writing it.. One time I did it and always get back same value, but in reality, that value wasn't read from chip and was just bus echo, because, there was a fault in one buffer IC.. 😂

Amazing work, more than impressed

Thanks for the video.

Absolutely AMAZING. I like a bunch of repair channels and 8-bit coding channels... But you just do both. Really well done. I would also love to see more coding. Keep up the good work

It was amazing, great job!!!!

Excellent! Thanks for the vid.

Cool video Noel thanks dude.

Great video, thank you! :)

wonderful!

That was great! Way beyond my capabilities.

Again.... well done diag and cool to see you coding in asm...my favorite! Interesting where that corrosion was located. This is why you don't drink or eat around your machines(but every one of us nerds do it!) xD

It's always so fascinating to look at coding stuff. Makes me wish I could wrap my head around it.

Great video!

Great video I think your skills are improving! Remember too PCB traces can be open/ short or high impedance. Liquid damaged?

Really enjoyed the programming portion :-)

I'm sat here screaming there is corrosion around the 74 chips, check them all! Great video.

Awesome diags coding there!

Definitely cool!

Great job! and thanks for your diagnostic tool! :) Useful

I'm currently learning to write z80 assembly for my CPC6128 ... I would absolutely love to see you create a video series (or even a couple of one offs) demonstrating development of some programs for the CPC (or any other z80 8bit to be honest)

Oh my!, that Zacks book, so many memories, back in the days somebody passed me photocopies of some of its pages, I don't think it was the full book. Little trivia: The Z80 ALU is 4 bits wide only, so, if the MC68000 is considered a 16bit MPU because its ALU is 16bit wide, the Z80 should be considered a 4 bit micro. V.g. In order to add two registers it has to perform two passes through the ALU. I didn't know that in the 80s, it wouldn't surprise me if Zilog kept it confidential. Thumbs up, keep on the good work!

Love your diagnostic program. Would be cool if you made it test for everything possible, then for all the decent 8 bit computers with the same user interface, (You can skip C64 and BBC) :-)

Another great video and thank you for giving us your awesome work on the diagnostics tools. That will be very helpful. But I can only buy an Dandanator mini v1.3 on ebay. There is no other available in Germany. And my Schneider CPC has got centronics interfaces so it will need adapter.

Noel, really interesting video. I would certainly be interested in any assembler programming for Sinclair, Amstrad or Commodore machines.

Really liked this video - would love if you could show us how to get started with assembly programming on a Spectrum or C16.

🐨 Another Gem.. APU I dropped a 👍

On 2 and more-layer boards with metalized holes, there is a potential problem with top traces that if the solder does not full overflow to hole and the metalizing in hole is broken, there will be no connection of soldered pin with the top trace. Maybe some people know about it, but most don't realize it.

nice job on the fix Noel..that was a really interesting one!... and the Diagnostics.... seriously AMAZING!... top effort mate! ...just wondering for complete-ness, if a disc and tape diagnostic could be added... i dunno how yad go about it... maybe write tracks directly and read them back?.. same with the tape?.. i guess that wouldnt help with disc head alignment problems tho... just a thought...

Noel needs a Sherlock Holmes hat and magnifying glass ... they would be very appropriate for the “chip detective”. 🕵️‍♂️

Hm. I have a few CPCs in a box that I'm supposed to test. Maybe I'll get myself a Dandanator + your diagnostics and get started. :)

Hi Noel, thank you for another great video! Quick question: at what temperature do you usually use your desoldering station? I am asking because I have a lot of clogging issues with mine and I think it may be related to temperature settings. Thanks!

Zak's books were awesome.

Fruity Frank in the floppy disk... Oh what memories!

"I wonder what got that chip so bad." I have seen that where someone's drops of sweat landed on boards and was never cleaned off for years. When I first saw that chip in the video, sweat was my first thought. ETA: I noticed what looked like discoloration on IC211 below the floppy disk controller as well.

I get the same kind of excitement and wonder in embedded now that we did from 80s micros.

Once again, admirable persistence and calmness! About the diagnostics program, could it be possible to output sound in the form of beeps to indicate where the fault is? Like modern computers do.

No menos mal! Well done! Nasty looking corrosion, any clues on the chassie what had been leaking into it?

Anything amstrad I'm there!

Sounds like whatever was spilled in there may have shorted out the pins on the inverter, seems logic ICs don't like fighting their own outputs for who is correct.

Just wow

To replace an Amstrad IC 32K rom, would EPROM AM27C256-90 or AM27C256-120 be suitable?