Stumping Black Screen Amstrad CPC 464 Repair
Рет қаралды 42,199
Күн бұрынThis Amstrad CPC 464 had resisted all previous attempts at being repaired. And since I like a good challenge and I have a soft spot for Amstrads, I decided to take it on. The symptoms were a black screen with no video signal at all. It turns out, multiple faulty components made this repair more challenging than usual.
Chapters:
00:00 Intro
00:43 Visual inspection
02:23 Voltages
04:48 Clock signals
08:24 Video signals
10:32 ROM
12:30 CRTC
14:38 Cartridge ROM
17:50 Gate Array
21:06 EPROM fix
23:54 Conclusion
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#amstrad #retrocomputer #repair
@OTuit 2 жыл бұрын
Your screen presence, technical expertise and video quality easily makes this my favorite retro channel!
@thebyteattic 2 жыл бұрын
Ahh, a proper Noel video! Great job, both fixing, understanding, and explaining!
@NoelsRetroLab 2 жыл бұрын
Thank you! That means a lot coming from you 😃
@richardblake8275 2 жыл бұрын
Yes, these videos are the very best kind.
@barowt 2 жыл бұрын
These old boards are so much easier to learn the concept of how all of the components work with each other. Also awesome that we have come so far..
@nutsnproud6932 2 жыл бұрын
I'm glad you got it working. I wondered why there was a 64K EPROM in and A15 was not strapped low or high but you worked it out in the end! I hope somebody does make gate arrays available in the future. I would suggest you cover the erase window.
@melanierhianna 2 жыл бұрын
You could duplicate the ROM in both halves of the larger EPROM. It doesn’t matter if A15 floats then because it will read the same byte value regardless.
@OzRetrocomp 2 жыл бұрын
OMG... I've been trying to fix a BBC Micro B+128 for the last few days that's showing almost exactly the same symptoms on its 6845 as the CPC 464 in this video. The timing is unbelievable! Thanks for giving me some idea of what to check out next.
@NoelsRetroLab 2 жыл бұрын
I have confirmed that if the 6845 is not initialized, it doesn't generate HSYNC, so start looking there. Good luck! 😃
@DavidBrant 2 жыл бұрын
Great vid! Always enjoy your insight into your retro repair work. Shows a deep understanding of computer logic systems. Respect!
@NoelsRetroLab 2 жыл бұрын
Much appreciated!!
@another3997 2 жыл бұрын
That was an excellent diagnosis and repair video. It really is a pleasure to watch someone who is both methodical and meticulous working through a problem. 🙂 I need to try out an Amstrad CPC, as I never actually used one back in the day.
@capybaratech377 2 жыл бұрын
That was amazing. Job well done Mr. Noel. God bless you
@allford1971 Жыл бұрын
Just got my first Amstrad CPC 464 so I’m catching up on all your videos on the Amstrad before I switch it on
@keiiko 2 жыл бұрын
THIS is exacly what I like about retro computing, solving the mysteries 👍
@MichaelDoornbos 2 жыл бұрын
I’ve never seen one of these in person, but after watching several of your repair videos I feel pretty confident that I could take a good crack at one. Excellent video.
@NoelsRetroLab 2 жыл бұрын
Right? It's a pretty straightforward system all things considered.
@TranceTrousers 2 жыл бұрын
Fascinating to watch you slowly figure out what was wrong with this board, and congratulations on fixing it!
@StatusFIX 2 жыл бұрын
while working through your videos and listening to your exsplaintions while reading "an introduction to microcomputers" and trying to crame some learnings , perfect afternoon
@sammy61187 2 жыл бұрын
Noel i swear you have the greatest T-Shirt collection ever p.s fantastic video new subscriber glad i stumbled across you greetings from Australia
@NoelsRetroLab 2 жыл бұрын
Welcome aboard! And yes, the t-shirt collection is something I've gathered over the years, and now I go out of my way to print a t-shirt if I'm working on a new system 😃
@xxTeamFearLessxx1 2 жыл бұрын
@@NoelsRetroLab Oh yeah, this is it. He makes no video, because he does not own a c-16 shirt!
@horusfalcon 2 жыл бұрын
Thanks for sharing the mistakes you made along the way. That helps us all profit from those mistakes, and learn more. You always keep it real, and that's a great thing, man.
@NoelsRetroLab 2 жыл бұрын
Thank you! Glad that helps. I really try to show the whole process, not just the pretty bits. We all make those kind of mistakes and it's fine 😃
@doc_sav 2 жыл бұрын
Great show as always, Noel.
@AS-ly3jp 2 жыл бұрын
Great video as always. It is like watching a murder mystery getting solved. Just great!!!
@sinuheheras 2 жыл бұрын
Buenas! Aquí un seguidor Español, me encantan tus vídeos son una pasada, con cada video aprendo electrónica y retro informática! Gracias por cada uno de tus vídeos, son oro! Te escribo en castellano porque en uno de tus vídeos dices que estás en el norte de España y porque muchos de tus cacharros están en Español, espero que estés siendo feliz en este humilde país. Un abrazo
@NoelsRetroLab 2 жыл бұрын
Gracias! Pues sí, sigo por aquí en Asturias y como viste, casi todos los ordenadores son españoles porque son los que encuentro por aquí 😃
@gertsy2000 2 жыл бұрын
Detective Noel and his AND OR NOR logic. Well done. Most interesting.
@johnsonlam 2 жыл бұрын
I love the walk through with the mistake, each time the correction really help to improve skill, awesome!
@NoelsRetroLab 2 жыл бұрын
Glad to hear it!
@kjamison5951 Жыл бұрын
Genius! Thanks, Noel!
@SirHackaL0t. 2 жыл бұрын
A great video and your presenting style is excellent. 👍
@SatansLtlBaby 2 жыл бұрын
love these diagnostic vids. great work
@NoelsRetroLab 2 жыл бұрын
Glad you like them! 👍
@bitschips 2 жыл бұрын
Me encanta la didáctica, cómo lo explicas, me ha encantado todo el recorrido buscando el problema y descartando posibles fallos. Muy interesante la diferencia del pin A15. Gracias!
@johnnygray8160 2 жыл бұрын
Great episode! Loved it. Thanks for the hard work!
@NoelsRetroLab 2 жыл бұрын
Glad you enjoyed it!
@AlexAnder-or3kq Жыл бұрын
Smart brother. Excellent vid… love my old cpc464 I picked up from a rubbish pile including green screen monitor. All I had to fix was power input capacitor and it’s all good
@retrohaxblog 2 жыл бұрын
Excellent video sir! Loved it!
@macstar8317 2 жыл бұрын
Great video as usual. Excellent detective work too.
@NoelsRetroLab 2 жыл бұрын
Glad you enjoyed it!
6 ай бұрын
Great video and breakdown, thank you!
@zedfragg4134 2 жыл бұрын
This was an amazing video, throw back to the first computer I have ever used (At 3 years old). Love it.
@PabloSantiagoCebak Жыл бұрын
very good video. All components are good in conclusions. like your work.
@sebastianbort8512 2 жыл бұрын
New video from the best retro computing channel, great
@NoelsRetroLab 2 жыл бұрын
Wow, thanks!
@voneschenbachmusic 2 жыл бұрын
As always, well done!
@TaberBucknell 2 жыл бұрын
Detective shows are great! 👍
@SidebandSamurai 2 жыл бұрын
Great work. You pealed the problem back layer by layer like an onion. Not only that you are teaching me board level trouble shooting skills. You are awesome! I would love to see you make the FPGA for the Gate Array. You could make it a series and run these mixed in with all your other content.
@SpeccyMan 2 жыл бұрын
You peel the layers of an onion. Bells peal!
@noureddinebenakrim5458 2 жыл бұрын
I watch your videos every day
@demofilm 2 жыл бұрын
Amstrad cpc was one of the best in its time. The shear count of available games is massive
@wittonleung8732 2 жыл бұрын
My two sleeping CPC464s sincerely respect this video!
@NoelsRetroLab 2 жыл бұрын
Time to wake them up!
@Berend70 2 жыл бұрын
Well I don't (and never had and probably never will) have a amstrad but i like your analyses very much! Keep up the good work Noel!
@NoelsRetroLab 2 жыл бұрын
It's great to hear that someone without a particular attachment to Amstrads can still enjoy the video. Thanks! 😃
@GadgetUK164 2 жыл бұрын
Great repair =D I've got another CPC coming up, will give your diagostics ROM a go!
@NoelsRetroLab 2 жыл бұрын
Thanks! Yeah, I've done a few CPC repairs since I wrote it and it's come in really handy already (even if I say so myself 😃). Let me know what you think when you try it. I'm also happy to incorporate any feedback.
@104d_3rr0r_vince 2 жыл бұрын
Great job Noel!!!
@NoelsRetroLab 2 жыл бұрын
Thank you!
@user-pk7mb9is1e 2 жыл бұрын
very good as always!!!!
@ncbrady 2 жыл бұрын
very interesting video Noel ! I can't wait to see you do the same analysis with your CPC 664 :P
@NoelsRetroLab 2 жыл бұрын
You know, I already have that video down on my schedule for #janstrad 👍
@ASCIITerminal 2 жыл бұрын
Excellent! You can't have too many Amstrad videos.
@NoelsRetroLab 2 жыл бұрын
That's the spirit! 😃
@arbiter1er 2 жыл бұрын
Hey dude we own the same variable power supply! Absolute same model. Very useful
@deathshaker0026 2 жыл бұрын
Good work!
@one_b 2 жыл бұрын
Bwop bwop bwop bwop bwop bwop bwop bwop. Ram! Something pleasing about that while having coffee on a break and watching the repair unfold.
@KolliRail 2 жыл бұрын
Very good! As always!
@TotoGuy-Original 2 жыл бұрын
Well done that was a good interesting video always a pain when more than 1 problem present on something like this
@rockyhill3 2 жыл бұрын
Excellent attention to detail, that floating pin would have driven me crazy for a long time. Great video! I see that at a certain point you switched from Windows to Mac and I imagine it had to do with running the programmer software. Even though it's a Windows program, I run XGPro for my TL866 II Plus on linux under wine . Wine runs well on a Mac and XGPro might work as well. Again, Excellent video!
@braveheart9275 Жыл бұрын
Hi ...Great video. Thanks.
@xicorpt 2 жыл бұрын
Just noticed that the IC103 socket is reversed. A deadly trap for young players.
@NoelsRetroLab 2 жыл бұрын
You're right!! Good catch!
@SimonEllwood 2 жыл бұрын
Definitely testing the bits on a known good board is the easiest way round!
@NoelsRetroLab 2 жыл бұрын
For sure. It's just more of a hassle and you don't always have a good board with the right sockets. And, there's always the possibility of putting an IC so destroyed that it damages something else (but that's not likely, especially if you know the current draw is reasonable).
@VladoT 2 жыл бұрын
Well, this is good reason to learn Verilog and VHDL 🙂
@georgealibinisis4816 Жыл бұрын
Please make a new CPLD array!! Excellent video.
@davidcady6315 2 жыл бұрын
Wow to both your troubleshooting skills, as well as to the computer itself.. Amstrads were rather rare in here (now Slovakia / formerly Czechoslovakia), and mostly sold with the 'Amstrad-Schneider' logo. Only one local shop (that I can recall) had a few of these for sale, but unfortunately, without any accessories and programs for it - on top of complete lack of any documentation. Quite a pity, as later on in my life I found out how great these machines actually were. However.. Throughout the whole video I felt like I was still missing something essential, even fundamental in there, if I may say so - but finally, I figured out what it was.. . . . The cat :-)
@jagc1969 Жыл бұрын
Impresionante. Sencillamente impresionante.
@rondlh20 2 жыл бұрын
Great job, going to the core of the problem step by step. Would writing the contents of the ROM again at an 32K offset solve the problem too?
@annieworroll4373 9 ай бұрын
That soldering looks a lot like mine. It's messy, but consistently results in a working device, that's the most important thing. I should work on it though, which will help with more tightly packed PCBs.
@richshealer3755 2 жыл бұрын
What impresses me is that many KZfaqrs show their mistakes on camera. Like looking at the wrong schematic or the bent pin on the RAM. I don't know that I would have the confidence to show the world my errors. That is not meant negatively on the author as it shows what happens sometimes in the real world. I think my self criticism comes from watching years of repair shows on TV that rarely made mistakes while replacing a door frame or some such.
@projectartichoke 2 жыл бұрын
Good catch on that ROM, you read the chip number aloud a few times and it never even dawned on me.
@38911bytefree 2 жыл бұрын
NICEEE !!!!!. Good job.
@redace001 2 жыл бұрын
Love all the 8bit fun, can't wait to see what you pull out for SepTandy! I have a Model 1+Expansion Int. I want to get working with a floppy emulator like a Gotek. :D
@NoelsRetroLab 2 жыл бұрын
Thanks! September is going to be pretty busy personally, but I'll try to make at least one #septandy video. Possibly two, although it might become #octandy by then 😃
@YogSothoth1969 2 жыл бұрын
Well done, Noel, as always very informative and a pleasure to watch... Michael
@NoelsRetroLab 2 жыл бұрын
My pleasure!
@frankowalker4662 2 жыл бұрын
Nice diagnosis and fix. When I put 64K RAM in my ZX81 I had to do the same thing with A15 as it works best with 32K. :)
@NoelsRetroLab 2 жыл бұрын
Thank you! Yes, that's something to always watch out for. I was kind of kicking myself for not seeing it earlier... but if I had it wouldn't have been quite so interesting, so that worked out OK 😃
@SpeccyMan 2 жыл бұрын
You could control A15 with a little extra logic to have 2 pages of 32K. Not much use in BASIC but certainly useful in machine code programs.
@ismaelyutub 2 жыл бұрын
Clear, very detailed and informative as always. Well done, Noel. One trick to use 512 instead of 256 is to duplicate contents from 0-7fff onto 8000-fffff, thus A15 is not relevant. However, grounding A15 as Noel does is electrically safer that let it floating.
@NoelsRetroLab 2 жыл бұрын
Many thanks!
@lister_of_smeg6545 2 жыл бұрын
You could even burn the 464 ROM to the bottom half and the Diag ROM to the top half, then wire a switch to A15.
@arska6383 2 жыл бұрын
Grounding the A15 pin is the only real solution, as if it is left floating can confuse the the heck of the address decoding logic, and can result in total garbage data being read. Just never leave any relevant signals in "X" or floating input state. Leaving something unexpetdly floating can result also a current spike, especially in older CMOS chips that have essentially linear input to the CMOS pair.
@Cesar-ot1xk 2 жыл бұрын
Haces muy buenos videos,y sienpre se aprende una cosa nueva,saludos desde España
@NoelsRetroLab 2 жыл бұрын
Gracias!
@TMS5100 2 жыл бұрын
@18:45 wow, your drams make the exact same popping sound as mine when i put them in 😁
@WacKEDmaN 2 жыл бұрын
top stuff Noel...this makes me wanna get my board back out and probe around a bit..(i need a diagnostic cart, and some ram chips!) ...im really keen to see the gate array recreated..im thinking it shouldnt need an fpga...it should be able to be done with microcontroller and the right code...i was gonna look into it if i could get my board working!
@NoelsRetroLab 2 жыл бұрын
Some people are already working on a CPLD version and they contacted me, so I may be able to test a Gate Array replica soon!
@WacKEDmaN 2 жыл бұрын
@@NoelsRetroLab yay!..about time someone did it!
@antisoda 2 жыл бұрын
@@NoelsRetroLab Sweet!
@Wtfinc 2 жыл бұрын
this was fun
@jlucasound 2 жыл бұрын
You are a freakin' genius!
@intotron6708 2 жыл бұрын
Back in the days ... oh boy, that's long ago and was a good time. I had a CPC664 myself. I remember the German computer magazine c't had a project with the CPC6128. I think they added even more RAM to this. The important part: they had to modify the Gate Array and IIRC they also published the code for that. I do not have this in my archives, but I'm sure they have. A simple ask for help could meet some support I guess. FWIW and HTH
@cbmeeks 2 жыл бұрын
You should totally start a series on FPGA and creating the Gate Array.
@rapiqui 2 жыл бұрын
That would be awesome. Having some high quality videos like Noel's explaining how to implement a design on a FPGA would be something.
@TRONMAGNUM2099 2 жыл бұрын
Good job on the repair. Too bad about the Gate Array failing. Hopefully somebody figures out a replacement.
@NoelsRetroLab 2 жыл бұрын
Thank you. I'm actually just talking to someone working on a Gate Array replacement and I'm hoping to be able to test it. So that will be happening soonish I hope 😃
@northbrid 5 ай бұрын
This is a great video, I love it’s detail-oriented yet understandible approach. I have a faulty CPC464 and did the debugging steps saw in the video. In my case, the CRTC generates VSYNC / HSYNC signals, but the gate array does not generate interrupt signals out of them. What does exactly the interrupt code do, does it play a role in the initialization? I mean if I pull up the interrupt pin in the Z80, will it display the welcome screen, even if the interactive things will not work? Where do you get a replacement gate array? I have a 40008 to replace, but found nothing in ebay. As a last resort solution, can I install a binary counter between the sync and the interrupt signal, or it’s a more complicated logic than that? The rest of the gate array seems working. Thanks your answers in advance!
@charlesjmouse 2 жыл бұрын
Excellent as always: Questions because I really don't know and I'm somewhat curious, not stupid... Is the logic known or yet to be reverse engineered? How complex is the Amstrad gate array? In other words does a replacement need to be implemented in a CPLD or will discrete components do as in the gate array found in later Spectrums? Indeed could an EPROM implementation work such as found with the 'less good' C=64 PLA replacements?
@ianwilliamtait9909 2 жыл бұрын
That EPROM. How long has it been sitting around exposed to light?
@johndododoe1411 2 жыл бұрын
As an alternative, just repeat the ROM image when burning the chip, so the higher address bits don't matter (except as a source of noise).
@Mikemk_ 2 жыл бұрын
That's a better solution since it doesn't require the extra wire.
@keeleyhoek 2 жыл бұрын
This is not really a good idea: leaving the high address bit floating can cause the voltage at the pin to enter the intermediate voltage range between high and low, which can lead to the internal switching logic inside the device to rapidly oscillating. This causes high power consumption and can even damage the device (especially after some time). e.g. See the Texas Instruments application note entitled "Implications of Slow or Floating CMOS Inputs".
@wayland7150 Жыл бұрын
A15 pin according to the 27c256 should have been VPP not NC.
@JVHShack 2 жыл бұрын
Noel making a FPGA based gate array? I say "Go for it!" I would attempt it, but I'm having trouble just making a 16-bit ISA riser card with only 2 slots...
@NoelsRetroLab 2 жыл бұрын
We'll see. If not for this, I'm sure I'll end up making an FPGA for something else. I really like the idea of replacements of custom chips.
@moterov4 2 жыл бұрын
Good video. If suggestions are allowed, I would propose one: eg. a RAM expansion on motherboard, upload it to 128KB for CPC464.
@jlinkels 2 жыл бұрын
Good troubleshooting. Not many technicians still can do that. Just one thing, I would have checked the supply voltage on the pins with the scope as well. With a digital meter, what you see is not necessarily what it is. Or at least you don't know what you don't see. I still prefer an analog meter.
@SidneyCritic 2 жыл бұрын
If the power supply is reading low on the MB you would assume the leads have resistance, ie, losses. Or maybe the external bricks have a higher voltage, eg, 5.2V.
@rapiqui 2 жыл бұрын
Well done (again)! I really appreciate the detail put in explaining every possible cause and further analysis. What about if he had duplicated the same ROM binary content on the 27C512 despite having A15 floating? Un saludo :)
@granpawa 2 жыл бұрын
That would have worked perfectly. I do that all the time and it's the easiest solution when replacing a 27C256 with a 27C512.
@rapiqui 2 жыл бұрын
Thanks for confirming :)
@NoelsRetroLab 2 жыл бұрын
Thanks. Duplicating data is something that's often done and it works. I don't know about the long-term effects of having a floating input though. It could be that some transistors could have a reduced life because of that? Not sure.
@granpawa 2 жыл бұрын
@@NoelsRetroLab So far, I've never had any kind of problem with that setup. I mainly used that trick in Apple IIc (converted from rom 255 to rom 4X). Can't say it's 100% safe but as far as my experience goes, it is working without any side effect.
@SianaGearz 2 жыл бұрын
I think when you burn a smaller image into a larger capacity EPROM, it would be prudent to just replicate it as many times as it takes to fill up the EPROM. Then the specific value of unused high lines doesn't matter. But then leaving them floating still isn't ideal anyway, because no specific behaviour is guaranteed.
@charlesdorval394 2 жыл бұрын
Looking forward to the FPGA videos ;)
@NoelsRetroLab 2 жыл бұрын
Haha, I'm sure I'll get there some day 😃
@markretro3612 2 жыл бұрын
another excellent video ... ouch i was putting my money on the CRT controller as well ... that diagnostic program you made is excellent .,...i notice that the counter resets after a certain amount of cycles in soak mode.. i think at 255 ?? got one that it is showing 7 bad chips out of the 8 I'm not ready to unsolder them yet until i am sure as its one of the small boards that are sooooo delicate
@NoelsRetroLab 2 жыл бұрын
Thanks! You're right about about counter wrapping around (I never tested it so far). It's just a byte internally. It might be possible to extend it to a 16-bit number. I'll have to check (it needs to survive a reset and a whole RAM wipe in between iterations).
@markretro3612 2 жыл бұрын
@@NoelsRetroLab i like to work them up to temperature as i have had some spectrum +2's that work great then after a few hours the ram failure seems to start
@laurentvoisin8129 2 жыл бұрын
Always thé n'est Noël ! by the way, I love tour shirt !👍
@NoelsRetroLab 2 жыл бұрын
Thanks! 😃
@laurentvoisin8129 2 жыл бұрын
Lol ! I tried to wrote 'always the best'. Automatic corrector doesn't want to cooperate.
@Zadster 2 жыл бұрын
Has the gate array been reverse engineered yet? Designing an FPGA is the relatively easy part.
@SatoshiMatrix1 2 жыл бұрын
I love these sorts of videos but I am not very technically savvy. What exactly does a gate array do?
@ronnyverminck2741 2 жыл бұрын
Is the nodge of the ROM socket on the right side instead of on the left side. Can cause problems for someone who isn't aware of this when replacing a ROM. Great diagnostics btw :)
@NoelsRetroLab 2 жыл бұрын
Yes! Good eyes. Someone else mentioned that. I can't believe I didn't catch it. Probably because it came with the EPROM already on it and I missed during the initial inspection.
@winstonsmith478 2 жыл бұрын
You mentioned in a previous video that you reside in northern Spain. I spent some time in Galicia. A very pretty and green area and I learned that the claim that "The rain in Spain falls mainly in the plain" from the musical My Fair Lady is most definitely not true after visiting the north and then the central plains of Spain.
@NoelsRetroLab 2 жыл бұрын
Haha, very true. Quite the opposite actually. I'm in Asturias, so right next to Galicia and very similar kind of landscape.
@FilipeNeto616 2 жыл бұрын
@@NoelsRetroLab Once I was dinning near Cangas de Onis and it starts rainning, the waitress, out of the blue, commented with us "és así que nosotros regamos los campos"... don't know why, but never forget the way he said it
@winstonsmith478 2 жыл бұрын
@@NoelsRetroLab That entire area is beautiful and green and the people are very friendly. I really enjoyed my time there and didn't want to leave nor did my coworkers.
@SpeccyMan 2 жыл бұрын
"The rain in Spain STAYS mainly in the plain." is the correct quote from My Fair Lady.
@LuisFCorreia 2 жыл бұрын
About lower voltage with that power suply, maybe increase wire gauges that go from PSU to mainboard you are probably experiencing loss from high resistance wires
@hansu-nihon 2 жыл бұрын
Nice repair video Noel, but where can I buy that Amstrad t-shirt that you are wearing?
@NoelsRetroLab 2 жыл бұрын
I got it from an online t-shirt store, but I'm going to see if I can put one on my store. I don't think the Amstrad brand/logo is currently actively used, so hopefully that's fine.
@swisspeach67 2 жыл бұрын
Is it possible to have two different ROMs in the same EPROM (i.e diagnostics and regular) and switch between them by pulling the highest address line high or low?
@SpeccyMan 2 жыл бұрын
It is, with the addition of a little extra logic circuitry or even just a manual switch for A15.
@Retrobution 10 ай бұрын
I am stumped with my one I just had in here, I got this one for myself as it was kept in a case in pristine condition! It is a 1983 model with no ribbon cable ports at all the motherboard is a Z70100. When it's switched on you get a garbled glitch image, switch it off and then on and a sort of chequer board screen shows with some artifacts and that is all. The chips feel all warm except for the AMSTRAD 40009 chip which is stone cold. Do you have any advice for this one? thank you
@NoelsRetroLab 10 ай бұрын
Is the glitch image still in the center and you see the border the way it should be? If so my money is on a RAM chip (even if none of them stand out). Pop in the diagnostics ROM and it'll tell you almost for sure.
@Retrobution 10 ай бұрын
@@NoelsRetroLab I have tried to reply here but for some reason the messages are deleting :(
@Retrobution 9 ай бұрын
@@NoelsRetroLab It was one single ram chip that was bad! I replaced it and all is well. Connecting the diagnostic rom would only display a glitched screen, error beeps and then giant numbers on the screen with coloured bars until this ram chip was replaced. thank you for your help in determining this!
@armando92 2 жыл бұрын
Don't know why but i keep hearing Gatorade instead of gate array, cant unhear now :p
@NoelsRetroLab 2 жыл бұрын
You're not wrong. You're not wrong... 🤣
@matthehat 2 жыл бұрын
Something that I've had success with in the past when using the wrong ROM capacity in a system is burning the ROM with the data repeated across it. My BBC Micro expects 128kbit ROMs in the sideways slots but when I haven't had any to use I've used 256 or 512 kbit chips and burned the data in either 2 or 4 pages so that no matter how the floating address bits are interpreted by the ROM the data will always be the same. It's not something I'd rely on long term, but it hasn't let me down yet.
@darrengoodridge1575 2 жыл бұрын
DO the FPGA Project Noel!!!!
2 жыл бұрын
Hi, some people burn the image twice on the EPROM to handle the floating pin, but I am not sure it is a stable solution (even if it probably works, at least most of the time). Do you have an advice on that?
@SpeccyMan 2 жыл бұрын
The advice is: NEVER leave a pin floating!
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