Always Check The Basics First - Amstrad CPC Repair
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- Опубліковано 9 чер 2024
- Some repairs are epic and others... not so much. But it's really important to always do the basic checks before moving on to other things to identify easy faults as quickly as possible.
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Chapters:
00:00 Intro
00:57 Initial checkup
02:45 Clock signals
04:28 Candidates
06:25 What are those signals?
08:26 Conclusion and announcement
Music tracks:
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More awesome music by McKlain: www.mcklain.com
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#amstrad #z80 #retrocomputer - Наука та технологія
Hi Sir, I wish all the luck with you, your family and retro-computers in this moving process.
Thank you!
Good luck with the move
Yes, good luck with the move as well. Hope you're moving to the West Coast. :) Would love to meet you.
The thesis of this video is so super important in all things troubleshooting. Excellent video!
Wishing you all the best to you and family with your move :)
Personally I like seeing your content even when it isn't a super tricky solution. I'm sure I'm not the only one who misses your content when it's been so long since the last video. I'm trying to learn 6502 assembly and for me it's a struggle. But videos such as yours help keep me enthused about retro computing in general and have a positive influence on my own motivation. Thanks! I think I'll branch out to z80 assembly in future. Good to see the retro community alive and well, not just repairers such as yourself, but enthusiasts who want to keep their computers in working order and not behind glass in a museum.
The old M1 trick. Great short video Noel. All the best with the relocation.
All good wishes for you move, and WELCOME to the USA!
That Amstrad T-shirt reminds me of when I used to install satellite systems and used to keep the vinyl Amstrad stickers that were supposed to be stuck to the dish for our tool boxes and other things, happy days! 😎
I had a CPC464 back in the 1980's, and although I don't repair any electronics or even own a retro computer, I love watching your videos and find the repair process fascinating. Good luck with your house move, and I look forward to when you get to make more videos in the future.
good luck with the move and looking forward to seeing the new RetroLab! :)
Thanks Noel, as a fairly dedicated 6502 man I'm looking at the Z80 in a new light mainly as a result of your videos! Hope the move goes well and best wishes to you and your family.
Have a good move! See you after settling in
My best to you Noel!!!, will wait for your next video!!
Great to see that sometimes these repairs are not that dificult, and just involves replacing an easy to find component (although knowing what to replace is never easy :-) ).
Thanks for the video and good luck with your relocation!!
That thumbnail reminds me of a simple repair I had many years ago. I bought a 1200 baud modem from a Radio Shack outlet store. It didn't work, so I did a visual inspection and found that the main IC had a leg sticking out of the socket. Worked fine after I pulled and reinserted it, making sure ALL the pins were connected. I wish I had time, energy, and money to learn more about electronics and repair. I've been a "hobbyist" for 40 years, but I know there are some large gaps in my knowledge.
I used to repair arcade machines back in the early 80s, and never came across a broken Z80 MPU !!
Hope the move goes smoothly.
9:47 Yes, it will be very interesting and informative. Happy to hear you plan to make videos about your new lab. ¡Buena suerte!
Best of luck with the move.
Good luck Noel, look forward to new material when it comes. Video like this particular one are invaluable, especially when you cannot see the wood for the trees!
My favorite example of this from my experience was when I couldn't get output from display port on my desktop. Spent a good 20 minutes.
The problem? the cable wasn't pushed in all the way.
Great video noel , and good luck with your move.
Good luck on the move Noel. It is the same with most IT related problem solving. Start with the basics and methodically work through.
User: My PC isnt working
tech: Ok, is it plugged in?
user: has left the chat
double check the basics. My commodore 64 had 4.5 volts and was working fine but once I plugged in the 1541 Ultimate 2+ cartridge it was glitching colors. Still works fine, but the colors are off. It took several chip swaps before I realized that the U2+ was causing a voltage drop down to 3.5 volts. It's amazing it even worked like that at all. Ultimately the cause was the cheap POS MIDI cable I bought to use as a power cable. I have a new power cable (same power supply that I built myself) and now it gets 4.9V even with the U2+ plugged in. It was a basic problem that I missed.
Good luck building a new lab of 110v equipment. Look forward to your US based videos
Thanks 👍
Thanks for all your very interesting videos and best of luck with the move!
So good to see you Noel, all the best and have a safe movement trip...Take care! Michael...
Good luck with the move - it will be interesting to see you build a new lab in the states
We would love to see highlights of your move! Thanks for all the interesting content!
Wow! Moving to USA, that is a big change. I know you've spent some time there, I asked about your American accent once and you told me, but still moving to a different country is a huge thing. I am guessing we will be seeing more C64s and very less Sinclairs and Amstrads from now on. I wish you and your family a safe trip and best wishes in your new life. It will be fun to watch you build a new lab, so keep them videos coming.
I wish him all the luck in the world but I’m not interested in C64’s at all, also they have bern done to death with other creators, maybe Atari content might be good, hopefully it’ll be varied.
@@SteveInScotland
More Atari content would be fantastic!
Welcome back to the US! Hopefully your move will be smooth and as trouble free as possible. Looking forward to your next video, whenever that might be.
Solid stack of Z80's there! :D
Noel thanks for the video and best wishes with the move. I want a CPC now I'll try and get one with the board you showed more options for keyboard and gate array.
Buena suerte con la mudanza!
Good luck on the move
Best of luck with your move -- I've really enjoyed your channel and have learned a lot. Perhaps we'll lean why you're moving to the US in a future episode. I'm looking forward, in time, to seeing your new lab setup.
Best wishes for the move! We'll be here when you are set up to make more videos.
Good luck with the move :)
Thank you for this video Noel...very instructive.. (Y)
Wow, big move coming up! Good luck!
Please have a safe and successful move! Bon voyage!
Congratulations Noel.
Good luck on your move. I know how you feel I'm also moving Just a hundred miles not intercontinental but packing away the workshop bit by bit so I can continue to work is a pain!
great video
Amazing how all these signals turn into things like Rolland on the Ropes...:)
Great vid and informative... Rolland would be proud.. :)
N x
I hope you move goes more smoothly than some of the computer repairs
I was wondering what was going on with the lack of videos lately. Good luck on the move (it's never easy), once you're settled I may have an interesting repair for you with a computer that has little (if any) documentation. A Panasonic MSX TurboR FS-A1GT :)
Hope all goes well for you soon !
Woohoo, welcome new neighbor!
I Wish you the best luck on other side of the ocean. Best regards from Portugal.
Great video! Really shows you know your way around the board. What state are you moving to?
Good luck with the move! Seems it is not the first time you do this :)
Hope all goes well with the move. :-)
quite a timely vid!... i feel like you made it just for me! LOL
....now ya got me wondering if my z80 is bad! (i realised my other z80s are CMOS and not gonna work in the CPC!)...the M1 line is about the only one i havent checked!
good luck on ya move Noel...
nope not my z80... works fine in the z80-mbc2... gotta be bad logic or bad ram...
Very interesting.
exellent!
Très bonne vidéo
Hi Noel, glad you are doing good, was wondering why the delays on videos, but now I understand, we wish you an uneventful trip, take care and hope to see the next video soon. One question, did you try that Z80 on another board?
Thank you! No, I didn't get a chance to test that Z80 on another board. It would have been interesting to see if it was just the M1 line or if it was completely dead.
Oh no! Less NRL videos in the near future. :( But, I hope the move is good for you and your family. Very informative video, as usual - thanks for sharing!
Wish you a success life in the USA, :) hope to see your videos again, we will miss you
You should definitely put the easy ones up as UA-cam shorts or something 🙂
Spain is the best place for live, and you know. Come back soon.
Perhaps the CPU was from a Spectrum, as you said the Spectrum doesn't need the M1 line and the expansion port has the - 12v line next to M1, so many Z80 in those get their M1 fried from moving the connector with the computer on.
Perhaps someone tried to replace the CPU in the amstrad with one of those semidamaged ones and couldn't make it work and though the problem was elsewhere.
I came here to say something similar - this CPU might work as a replacement for a Speccy CPU right?
@@bencollier3758 For normal operation it should if only M1 is damaged, but for example Divmmc devices need a working M1.
Thanks for the fantastic videos. I am going to ask the obvious. What does the broken Z80 do in a spectrum?
Good luck with moving to the US
Very nice video!
7:18 How does the gate array use WAIT signal to access RAM?
The purpose of the WAIT line is to make the RD, MREQ, IOREQ and WR signals longer for slow components. The address line and data line won't be put in high-impedance. However, BUSREQ line will let one put data and address lines in high-impedance, letting any other component master the bus.
Did the Amstrad have a bus transceiver or line driver to control RAM line inputs?
A check of the circuit diagram would answer your question. Yes. RAM A/D bus is separated from the Z80 by buffers/muxes under control of the GA.
BUSREQ is only actioned by the Z80 at the next clock, which may be too high latency for noise free video unless actions such as locking the CPU out for whole line times are taken.
Best of luck and wishes for the move, who knows somewhere down the line there could be a NRL/8-bit Guy collab?!?
Noel, after getting settled after your move, maybe you should troubleshoot & repair your bench PSU to correct the "unnatural" voltage drop that you've been putting up with. Now it's time for me to watch past the 02:58 mark in this video! ;)
Chip swapping is almost an art. It is like part swapping. You don't just want to be a part swapper just to find a problem. Though sometimes you do that. Same thing with chips on a motherboard. A few years back I purchased an Apple II with a video problem. So after cleaning and restoring chips / such (oxidation.). Plus knowing what is wasn't. I found a diagram of video tls chips. Once I verified change the 3 tls chips around change the issue. I ordered some replacements chips. Problem solved. Took me longer to find a idiot diagram with sections circled with what it was. Compared to fixing the issue.
Exactly. Whenever I have to resort to blindly swapping chips I feel I have "failed" the repair 😃
Any channel with my initials is always a great choice .🤣
Try to get an 240v and 50 amps outlet in the garage to charge a EV.
I thought about getting a 240V outlet just to run European computers, but I think it'll be simpler just to use a good voltage transformer. We'll definitely set thing up for an EV at some point though 👍
@@NoelsRetroLab Be wary of those voltage transformers. Tech Tangents did a video about one within the last year and he had to completely redo the internal wiring of the one that he got. I am planning a short move of my own and I want to install 240v outlets in my new place so I don't have to use that sketchy transformer. I bought one from a flea market a few months ago and I'm kinda scared to use it. I will use it if it's the only way to get something working, but only for a few minutes to test it.
Get a subpanel installed in your lab, then it is easy to run the circuits.
@@NoelsRetroLab Unless it's different in the US but all canadian homes are wired for both 110 and 220v. The drying machine in on the 220v circuit, so as long as you link to it and have a proper isolated circuit with easily identifiable outlets (not hard since they're completely different between Europe and NA), you should be fine.
@@Fularu same in the USA, normally 240 is for water heater, dryer so 240 is not normally a wall outlet. Getting the subpanel in the lab then you can have European outlets installed.
Z80s with faulty M1 lines are pretty common on Spectrums...It's fine until you connect them to a divIDE which relies on that line 😅
Hey Noel, what OLED screen are you using on your Amiga Gotek?
Yes, plese make video(s) about making new lab :)
Just wondering in regards to using an oscilloscope whether 100MHz is sufficient? Looking to upgrade from what I currently have which is an old Hitachi 40 MHz and thought I would go digital. Bit of a price difference between 100MHz and 200MHz (Hantek DSO5202P) - for just using as a bit of a diagnostic tool and checking the stuff like you have in this video. What are your thoughts?
Reading the specs we see that the 200MHz, 100MHz and 70MHz models in this line all share most of the hardware including sampling frequency. All three run at 1 GS/s shared between the two channels which means it's a bit limited above 100-133MHz *IF* both channels are enabled - as the number of samples per "wave" goes down it's forced to guess more and more, it only have 2.5 samples per wave at 2*200MHz which isn't very much, it's way too close to the Nyquist limit (effectively 2 samples).
This is pretty standard, even say premium brands like Tektronix sells "shared dual-channel 1GS/s" scopes in 50/100/200MHz variants, I suspect the difference is a software-limit and possibly more expensive capacitors on the front-end and/or better probes - and for some of these (non-chinese) scopes you can upgrade frequency via a license code (IE provably no HW difference on those).
This sampling limit slightly reduces the "value" of that higher frequency but it all depends on what you're going to use it for and it's not THAT uncommon to only use one channel, but it all depends on what you want to do. Only you can judge if it's worth, checking, something like 33% extra?
My feeling is that 1GS/s is overkill for retro computers of this vintage, I'd argue even the 40MHz scope you mention should be overkill for 8-bit micros.
I suspect you could use these 1GS/s scopes to tackle vintage Amiga/Mac/PC up to perhaps 75-90MHz for the 100MHz variant, and up to perhaps 150MHz using the 200MHz models (with judicious use of single-channel mode in some cases). OTOH having overkill on the sampling speed means you get a display that can be easier to interpret due to "nicer" wave-form displays and models cheaper than this often isn't in "scope form-factor".
Ref: Adrian's Digital Basement showed that even a shared 48MS/s scope-to-PC (Hantek 6022BE) was mostly usable for these types of computers (up to 4MHz 8-bit), the wonky trigger and clunky software was a worse problem than the sample rate!
He later tested a handheld shared 250MS/s scope and the main complaint was some rough edges in the software (Hantek 2C42, 40MHz). If you're in the market for that kind of handheld another options that often gets mentioned is the Owon HDS242 (another 250MS/s scope). I don't have either so I can't comment personally, I see that there's plenty of people who discuss them on UA-cam. And do watch Adrian's videos too.
many zx spectrums have been found to have 'faulty' z80s with missing or 'weak' /M1, but computer working normally, only showing the problem when an add on is connected that needs the /M1 for something, such as the interface 1, it has been said the /M1 output is quite easily 'damaged' by incorrect/slipped connections to the expansion slot or fault in an add on, surely the cpu designers shouldve buffered that signal? or would it introduce too much delay to it? it has also been said genuine zilog made ones seem to be afflicted more...maybe a substandard batch?
Which part of the US are you moving to? (I'm in Idaho up by the Canadian border)
Buen viaje y USA ciertamente necesita mas especialistas en Z80s, los gringos estan sobrecargados de 6510, llevales las computadoras europeas para que vean que hay vida aparte de las Commodore!
Let us know what area of the country you end up moving to, and follow-up with how you are liking it! Have a safe travel.
interesting…if this broken cpu will work properly at zx spectrum?)
3:27 - wrong time base of scope so it shows aliased signal (no proper sync on scope), try changing timebase to around 1µs or even less
Buen vaije. I am pretty sure that soon you'll have a bunch of new equipment in the USA now everything is so cheap on ali-express.
Last time i wasted my time to fix stuff's like this was maybe in the 90's
I heard that Sinclair got a good deal on Z80 chips with no M1 signal, as the Speccy does'nt use it, nor did most of the hardware expansions, it did'nt matter. LOL.
Good luck with the move. Sadly, you would have to replace most of your equipment anyway as America is 120V. :(
He could buy a step up transformer and power everything off that.
I haven't confirmed that story. An alternate version I read is that /M1 on the expansion board is very easily shorted to Vcc/Gnd and so it's often damaged on the Spectrum. Not sure which one to believe 😃
As for the voltage differences, you're right. I'm definitely getting a good transformer to be able to run all the European computers here.
@@NoelsRetroLab You will have to get one that converts 120V 60Hz to 230V 50Hz.
@@NoelsRetroLab I've just looked at the edge connector on the Speccy schematics, and M1 is right next to a 12V line. LOL. So that would explaine a lot.
@@NoelsRetroLab Most newer stuff is likely multi-volt but, yeah, always check first. Older stuff can be picky, but MOST US houses (IE apartments is more variable) have either 240V (homes, some offices) or 208V (larger offices & industry) easily available but it's obviously still at 60Hz. Yes, US is officially 120/240 or 120/208, not 110. Still, you may still end up with a transformer for some things.
If you DO need 230/50Hz or 240V/60Hz the cheapest way to get that for small loads tends to be via 12V, 24V or 48V DC intermediary. IE an US car/lorry/telco AC->DC converter plugged into mains, then feeding that DC voltage to an EU/UK car/lorry/telco DC->AC converter, probably with "pure sine wave" or a similar label (and it should specify a single-digit THD or THDv at 100% load) since if the hardware cares about frequency it may well get upset by "square wave" or "modified sine-wave" (only marginally better).
Also, *some* online (IE battery is always in the loop) UPS can do this if you have 208V or 240V, but it depends on them having a way to override output voltage (not that uncommon) and frequency (less common, auto-sense is defintely default but I've seen models which had it). Exploring this probably starts making sense around 500W+? Usually the spec sheet doesn't actually SAY whether you can force frequency so you'd likely have to read the manual to find out that part and again you'd want some kind of pure sine wave (see above for spec).
Or bringing over a power generator as part of the move can also work but you need to be careful to get one that's rated for "electronic loads" and honestly even then the power qualify isn't always THAT great.
Would the faulty CPU work in ZX spectrum?
Perhaps, if it was just the M1 line. I suspect it was mostly dead though.
Noooooo you said zee not zed when talking about a British computer how could you, 👍 video
The voltage drop on your bench PSU is not the bench PSU, its the chinesium red+black cable on the output. These are absolute trash with very thin aluminium (sometimes steel) wire, 1 Ohm is nothing unusual. Make your own one with a good quality solderable connector and 0.5mm² copper wire and good 4mm plugs on the PSU side.
80% of the time its something basic, something I wish I could hammer in my 3 new tech's brain. OMG the vision system is reading all kinds of crazy all hell is breaking loose on line X call a software developer FIRE FIRE FIRE. Come in next morning, grab the vision system alignment jig ... discover a couple nuts loose, grab a 25 cent spanner FFS
Its 2022. Just put that obsolete piece of technology in the garbage bin.
Europe/The EU (further and foremost) and the Euro is currently on a downward spiral - better to leave.
Thanks for another fantastic video!! Btw, given what you said, does this mean that the Z80 with the faulty M1 owuld actually work as normal in a ZX Spectrum?