Classic red herring plot twist! We all knew it was Paula. Jan was tugging us in that direction. And moments before we decide to tune out to see what sort of antics Chris Edwards was up to, Jan pops in the replacement Paula and…it doesn’t work! * epic plot twist music * This episode kept me guessing to the end.
I've had similar experiences trying to find a fault with swapping stuff out, but getting nowhere, only for something simple like that resistor to have been the problem all along and everything worked again, I think it's just habit to assume it's the big stuff first, which can be our downfall sometimes... :P
I also (falsely) assumed that I had already looked at the simpler stuff when I first tried to fix this particular one years ago. But yeah, these things happen to me a lot. Especially when I think I KNOW what the fault is. :D
As you point to at the end, start with the basics - voltages, clocks, resets... Glad you got there in the eventually. 😁 It must be annoying that such a simple fault has taken so long to find!
Yeah, I usually do that. For this particular one, I just assumed that past Jan had already done that (which he probably didn't, considering it was such a simple fault in the end). :D
It may be considered annoying, but that's the usual stuff you do when narrowing down possible sources for bugs, one step at a Time. HInt: sometimes, the simplest, smallest things have the biggest, nastiest effects - throwing one off the course on a wild goose chase. You only know it been that little small thing the moment you find it. so - relax, take a breath, cuss the sweet bejeeeezus out ot the thing if you are so inclined, and continue the hunt.
@@JanBeta That's what we german speaking folks call "betriebsblindheit" - and no, "not to see the woods for the trees" does not meet the true depth of meaning. it's especially hard to find one's own bugs, look over one's own assumptions. That's not bad. That simply is. Amithaba. IN the end, you got the bug by the cojones and implemented a nice and nifty fix.
I think you are absolutely correct. Just double checked on another rev 5 Amiga 500 and the colors are clearer on that. Definitely a 1 ohm. I have some of those, so I’m going to put the correct value in. Thanks!
At 31:30, compare the resistor in question to the ones at the upper right corner. I'm certain the resistor was actually supposed to be 1 ohm, but the 2.2 ohm will work in a pinch anyway!
The crash at the end of the chip ram test is normal in this version of DiagROM.. it's since been fixed :) (A major 2.0 rewrite version is underway) Additionally, the first CIA tests failed because, as the screen says, "REQUIRED LEV3 IRQ" and the IRQ tests failed :)
I've got a rev 5 Amiga 500 with a yellow screen also. It's so bad, that not even the diagrom will show anything on screen. I've hooked the diagrom serial port output to a serial terminal on my laptop, and it shows that most of the RAM is bad, which can't be right...? This machine used to work, then suddenly went yellow screen. Watching Jan do his thing here, is prompting me to go back and have another go at fixing mine.
If DiagROM shows all the RAM as bad, I’d probably take a look at the Agnus and the logic chips in the data path first. Sometimes if one of the RAM chips is bad, it can also lead to the rest of them not working properly until you replace the faulty one. Maybe one RAM chip gets hot, that would very likely mean it’s completely shorted internally.
The problem with rev 5 boards and larger ROMs isnt that they missed components - it's that they got the pinout for the ROM wrong! With only a 256K chip (like Kickstart 1.3) everything appears ok, but when using a 512K ROM the extra address line doesnt work.
Hi Jan, could you describe a schematics for the Kickstart EPROM adapter socket for early A500 boards you're using in this video, please? ☺I need to build it to myself but can't find proper info or even pictures of that socket done as DIY.
Here's a very in-depth description (you only need the "Electronics Part 1" portion of the post for most scenarios: bax.comlab.uni-rostock.de/en/hardware/amiga500/kickstart-eprom/
Hallo Jan. Wie immer ein Klasse Video! :) Ich hätte da eine Frage an dich, was bevorzugst du um die meist sehr staubigen Platinen von alten Computer zu reinigen? Ich sehe das du da mit der Bürste und Alkohol drüber gehst. Machst du das mit der kompletten Platine? Zumindest auf dem Video wirkt diese nämlich super sauber als hätte sie vorher ein Schaumbad genommen :) ...
Bei den meisten Platinen reicht Alkohol und eine Bürste. Staub puste ich meistens mit Druckluft vorher weg. Bei hartnäckigen Fällen benutze ich Wasser und Spüli (siehe z.B. meine „Saved from the Flood“-Videos). Wenn du danach ordentlich mit Alkohol spülst, überleben diese älteren Platinen das sehr gut. Commodore selbst haben nach Zeitzeugenaussagen Spülmaschinen benutzt, um ihre Prototypen zu reinigen in den 80ern. 😅
I am at 4:11 at this point. My first thoughts, without knowing could be one of the following three.... Fat agnus, agnus socket or gary. I lean 60 percent to gary at this point. Now to see what it will end with.
Neither my A500 nor my A2000 have any boot issues under normal operation, however, when I use a PiStorm, I get the same yellow screen exactly ONCE when the system is powered on, then it goes on to flash grey, white, Kickstart/HD boot. No idea why it happens, but it's the only time I've seen the yellow screen on an Amiga in person.
Maybe the PiStorm messes up the IRQ timings slightly. It basically takes over the CPU functions completely and probably the timing is pretty difficult to get right. (Merely guessing here!)
Check the voltages, it might be that your power supply is not delivering enough juice at startup. I have a third party power supply and had to turn up the 5 volts because it kept under-powering the Raspberry Pi (which shows up as lightning bolts if you have a display hooked up to the Pi).
Jan, it was a weird comment you did about swapping chips vs using an oscilloscope. Those chips are rare and expensive, your stash is way more pricey than a good enough oscilloscope to debug an Amiga. The educational value of just swapping stuff around until it works is not great. Fixing stuff is interesting because you learn stuff, this is not just about this specific machine working but about: what is an IRQ? How IRQs and sound can be linked? What is the architecture of the Amiga etc...
I would have to do a lot of research to be able to concisely talk about the exact inner workings of the Amiga IRQs. It’s quite complicated and I don’t understand it nearly enough to share my knowledge with the world. Also, you can still buy A500s for under 100€s and the whole chipset for around 50-70€s, even on eBay. A proper DSO is still a lot more pricy than that. Hope that clears up my point a bit.
The CIAs are just labeled like that in the A500. Left one is ODD, right one is EVEN. I think the engineers had loads of fun (and probably some beers) when they came up with the labels. The schematics have some hilarious jokes in them, too.
grüße jan...echt super hilfreiches video. hab das ma an meinen alten 500 versucht, der genau diese probleme hatte....hey, der widerstand ist auch durch!...danke für den tipp. PS: zum thema diagnose chip, kann man den irgentwo käuflich erwerben? das würde meine arbeit extrem verkürzen. ich muß immer noch blindfischen, und das dauert! (weist du ja bestimmt...🙂) ...lg, alles gute, ein echt herzliches dankeschön für deine arbeit und nen super herbst dir...dor GrauKappenHippie
Interessant! Hätte nicht gedacht, dass der Widerstand so ein häufiger Fehler ist. Cool, dass du deinen Amiga so auch reparieren konntest! Habe mittlerweile herausgefunden, dass der Widerstand in Wirklichkeit ein 1 Ohm 1/4W ist. Funktioniert auch mit höherem Wert, aber ich werde den nochmal gegen den richtigen austauschen. Das DiagROM ist Open Source, ich glaube es gibt Anbieter auf eBay und einige von den größeren Amiga-Versandhändlern haben die auch im Angebot. Ich brenne mir die regelmäßig selbst. :)
@@JanBeta hallo, danke für die antwort. ich hatte in den ami zusammen 4 tage investiert und hab den fehler nicht gefunden...tja, einmal deinen clip schauen, nachmessen und schon funzt es..! 🙂... eine frage noch zu zum brennen. ich hab noch nen eprombrenner für den amiga. kann man das auch mit diesem system realisieren oder hilft da nur n neukauf für nen pc?..lg,weiterso und ich bedanke mich herzlich...🙂
@KrautRockt Wahrscheinlich schafft der Amiga-Brenner noch keine EPROMs in der Größe, die du brauchst. Das DiagROM braucht ein 27C400 EPROM. Um das zu brennen, braucht sogar schon mein moderner TL866 einen speziellen Adapter (einfach weil der Sockel am Brenner physisch zu klein ist für 40-Pin Chips).
Double checked on another rev 5 A500 and it is a 1 Ohm in reality. Very much the same current limiting/fusable resistor that I had to replace in the previous rev 3 repair.
They are very similar. As far as I know, the main differences are maximum speed and the missing TOD clock in the Amiga CIAs compared to the 6526s. I heard that you can even use Amiga CIAs in the C64 to some extent but I've never actually tried it myself.
I guess it saw too much current at some point. I said in the video that maybe I plugged a Paula into the socket while the power was on or something. I've also seen resistors just randomly die of old age, although that rarely happens, it does sometimes.
What an interesting and enjoyable video. A good lesson in troubleshooting: if at first you don’t succeed, put it aside for a bit and come back later, if possible. Often when you come back after a bit you can attack the problem with a fresh perspective and renewed enthusiasm. I’ve got similar issues with one of my Amigas, now I think it’s time to revisit it. Well done Jan!
A good lesson in troubleshooting would have been to start with rule #1: thou shalt measure voltages ... but that would have been a boring video I guess 🙂
Great repair and very enjoyable video as always! Regarding the new resistor, I think you put a 1/4W there, and I think the original was 1W. Anyway, the lower wattage may cause that resistor to burn out eventually. It depends on the current consumption of the Paula.
I double checked on another rev 5 Amiga 500 and the resistor seems to be a 1 ohm 1/4W in reality. Pretty much the same as the one I replaced on the Rev 3 Amiga previously. Probably used for current limiting or as a fusable resistor for the Vcc (which somewhat makes sense). Thanks!
You mean the Agnus PLCC socket, I presume? The sockets Commodore used were just really low quality so they fail frequently, I’m not sure if Atari used similar shoddy sockets. If they are marginally better quality ones, they are going to be way more reliable.
The first step to finding the error is always to measure the voltages on the ICs. This can be done with any multimeter and is easy. The second step is to check the reset pulse. This can be checked with a resistor and an LED without complicated measuring equipment.
Very true! The thing is, I was so sure that I did the basic testing when I first tried to fix this one that it didn't even cross my mind to check voltages again. :D Apparently, I very likely forgot to do that the first time around, too. Didn't really have to probe the reset really in this particular case because the processor was clearly starting up fine.
Quality job :) Tho' it always amuses me to see the Insert Workbench Logo is painfully left handed which would always the single most uncomfortable way to insert a disc on the Amiga 500 considering the drive is on the right.
oh, and there is NO SUCH THING as LED blink codes. I have no idea who started this one, but it's completely *false*. The number of blinks is always the same and its just what the fault routines always do. The only thing that means anything is the screen colour. In this case, with a dead Paula, it could well be that spurious IRQ's happen... this would trigger a yellow screen as it's an unexpected interrupt. 1.3 probably disables interrupts early on in the 68000 (using the SR register in the processor) in addition to using the custom chip INTENA register. The freeze at the white screen in 1.3 is the system waiting for an interrupt to happen (it's how multitasking is driven), and because Paula is dead, it never happens.
@@JanBeta Sorry, couldn't resist. Also, could I ask you what is a good source of DRAM for an Atari 800XL? I have one that turns on with a green screen and wanted to start with the memory. All chips on bord are socketed so that would be the easy first step. It has Hitachi 4864-2 DRAM's in it now.
Just yesterday I returned from this year’s 4 day DoReCo party. Had my Amiga (Rev 8a) with me that would suddenly give me all sorts of color codes. First green, then red and then also yellow. Big „Oh no“ moment right there. Note: the machine had worked flawlessly just before going there. After testing a whole bunch of things from loose connections to dirt (everything was spotless) and a lot of head scratching and cursing, the issue turned out to be flux residue on the RAM expander (the Max Plain 512k one). So contrary to popular belief, sometimes alcohol is indeed a viable solution. 😅
A PLCC chip will only fit in the socket one way. One corner of the chip and socket are shaped differently. If the socket is rotated 90 degrees when installed, you won't be able to put the chip in correctly.
I think that’s true for some PLCC packages but not for this particular 84 pin version. You even have to rotate the Agnus if you use a different version for chip mem mods in the A500. This one doesn’t have any physical indentations on the chip side, just a pin one marker.
Great job! I figured the resistor would have been completely open or in the Megohm (which it was) and the 2k reading was because it was still in circuit. Was fun to watch.
From this repair, I learned to start with the basics, like checking the voltage supply to the chips. Then you could see if the reset circuit work, if the processor clock is there (if you have access to an oscilloscope, that is). DiagROM is also a huge help, even if it’s not very well documented. It at least can help narrowing down the fault most of the time.
@@JanBeta Thing is, I made a stupid mistake when I was gonna upgrade kick 2.0 to 3.1 on my rev 5 500. (Don't do soldering when your blood sugar is to low :P) I don't know if I killed the PSU (meanwell) or if something else happened but the power led only flashes once quickly when I put the power on, it's completely dead otherwise.
4.75 Volts is only 5% low anyway, well within limits. Usually when resistors fail it is very obvious! Smell is a surprisingly good diagnostic tool in electronics.
Great video, Jan! As for resistor colors: The only way I can remember them, even after over 45 years playing with electronics is this: Bad - Black Beer-Brown Rots-Red Our-Orange Young-Yellow Guts-Green But-Blue Vodka-Violet Goes-Gray Well-White Have fun! 😅
@@JanBeta For my complicated ways of memorizing stuff, the numbers 2 to 7 are a neat spectrum form red-orange-yellow-green-blue-violet ... brown is not yet properly glowing red so it's 1, black isn't glowing at all so it's 0. Grey is a less bright shade of white, and white is the hottest so they're 8 and 9.
G for grey actually? IIRC gold and silver occur outside the tolerance band only as negative powers of ten. But I might be wrong - wouldn't be the first time and won't be the last.
@@jussikuusela7345 - I believe you are correct. I stand corrected. I jumped the EIA color code and missed the Grey/Gray standard coloring! I corrected the error. Thanks!
Another thing to watch out for are those pesky hidden solder bridges - especially under sockets like the one for the SuperPLA on a C64 assy 250469 - any revision, for they all have that big fat SuperPLA. managed to get a solder bridge like mentioned before and boy, what a Hunt that has been. I changed and socketed all the ICs, even the small ones (and good it been, for there have been broken 4066s), but the main culprit has shorted a five-volt line with address line 0 on the superpla (pin 31 + 32 IIRC) - How to find that out? Well, the whole time the machine has shown a weird double addressing stuff, so I knew it had to be something in that vein. On the scope the traffic was depicted with weird shadows and odd traces not adding up to anything making sense. So I asked: Is it possible that there is a short between lines? And then I went and checked the SuperPLA Pins and 'lo! looksie looksie! I 've found what I been lookin' for. Take that, Bono! After a bit of wondering where the hell that short could be, I ve desoldered the SuperPLA Socket, and there, between the two pads, I've found the solder bridge. Removed it, put everything back together and the machine started to work like a charm. :) So, that was the long story of little me and the big bad SuperPLA - I hope you've found it elucidating in some way, the same as I find Jan's vids both entertaining and informative.
To make the circuit more reliable, install a resistor with a slightly lower resistance (e. g. 1.5 Ω) and with a higher power rating (0.5 W), it should fit that size.
No. The resistor is there to help prevent noise from the logic ICs getting to and from the sensitive stuff like Paula but it's also there as a fuse of sorts so increasing the power rating of the part could end up being dangerous in the event of a short on one of the user ports. Plus, how reliable would you like it to be? It's in a 30+ year old machine
"Thou shalt always check the voltages first!" 🙂You can just solder a 22 ohms resistor in parallel to that 2.2 ohms and get 2 ohms exactly. Solder it under the board to keep the good looks intact 🙂
A small little update video (please watch the original video first to avoid spoilers!): ua-cam.com/video/-4p-7bp0lGU/v-deo.html
Classic red herring plot twist! We all knew it was Paula. Jan was tugging us in that direction. And moments before we decide to tune out to see what sort of antics Chris Edwards was up to, Jan pops in the replacement Paula and…it doesn’t work! * epic plot twist music * This episode kept me guessing to the end.
Ein fantastischer Ansatz, der zu einer erfolgreichen Lösung führte, gut gemacht Jan! Danke!
Jan ho sempre detto che non esiste un problema che possa metterti in crisi,perche' sei il migliore!
Excellent work as usual Jan. Thanks for making lunch interesting!
Thank you! Hope lunch was tasty! :D
I've had similar experiences trying to find a fault with swapping stuff out, but getting nowhere, only for something simple like that resistor to have been the problem all along and everything worked again, I think it's just habit to assume it's the big stuff first, which can be our downfall sometimes... :P
I also (falsely) assumed that I had already looked at the simpler stuff when I first tried to fix this particular one years ago. But yeah, these things happen to me a lot. Especially when I think I KNOW what the fault is. :D
As you point to at the end, start with the basics - voltages, clocks, resets... Glad you got there in the eventually. 😁 It must be annoying that such a simple fault has taken so long to find!
Yeah, I usually do that. For this particular one, I just assumed that past Jan had already done that (which he probably didn't, considering it was such a simple fault in the end). :D
It may be considered annoying, but that's the usual stuff you do when narrowing down possible sources for bugs, one step at a Time. HInt: sometimes, the simplest, smallest things have the biggest, nastiest effects - throwing one off the course on a wild goose chase. You only know it been that little small thing the moment you find it. so - relax, take a breath, cuss the sweet bejeeeezus out ot the thing if you are so inclined, and continue the hunt.
@@JanBeta That's what we german speaking folks call "betriebsblindheit" - and no, "not to see the woods for the trees" does not meet the true depth of meaning. it's especially hard to find one's own bugs, look over one's own assumptions. That's not bad. That simply is. Amithaba. IN the end, you got the bug by the cojones and implemented a nice and nifty fix.
I always learn more from the difficult projects, and this one really tested your patience. Well done.
This might help my broken a500 with yellow screen. Nice video
Unfortunately, a yellow screen can mean a lot of things. But maybe it has something to do with the Paula in your A500, too.
@@JanBeta yes i have tested change all chip and i havent begin check voltage yet so it helps me to get forward ;)
Have had similar, shorted axial ceramic cap in the audio filter circuit burned up a 1 Ohm resistor that fed power to the quad op-amp..
that is not a 2 ohms resistor it looks like a 1 ohms (brown,black, gold)
I think you are absolutely correct. Just double checked on another rev 5 Amiga 500 and the colors are clearer on that. Definitely a 1 ohm. I have some of those, so I’m going to put the correct value in. Thanks!
At 31:30, compare the resistor in question to the ones at the upper right corner. I'm certain the resistor was actually supposed to be 1 ohm, but the 2.2 ohm will work in a pinch anyway!
The crash at the end of the chip ram test is normal in this version of DiagROM.. it's since been fixed :)
(A major 2.0 rewrite version is underway)
Additionally, the first CIA tests failed because, as the screen says, "REQUIRED LEV3 IRQ" and the IRQ tests failed :)
I've got a rev 5 Amiga 500 with a yellow screen also. It's so bad, that not even the diagrom will show anything on screen. I've hooked the diagrom serial port output to a serial terminal on my laptop, and it shows that most of the RAM is bad, which can't be right...? This machine used to work, then suddenly went yellow screen.
Watching Jan do his thing here, is prompting me to go back and have another go at fixing mine.
If DiagROM shows all the RAM as bad, I’d probably take a look at the Agnus and the logic chips in the data path first. Sometimes if one of the RAM chips is bad, it can also lead to the rest of them not working properly until you replace the faulty one. Maybe one RAM chip gets hot, that would very likely mean it’s completely shorted internally.
Nice Repair. 🦄
The problem with rev 5 boards and larger ROMs isnt that they missed components - it's that they got the pinout for the ROM wrong! With only a 256K chip (like Kickstart 1.3) everything appears ok, but when using a 512K ROM the extra address line doesnt work.
Good to know !
Hi Jan, could you describe a schematics for the Kickstart EPROM adapter socket for early A500 boards you're using in this video, please? ☺I need to build it to myself but can't find proper info or even pictures of that socket done as DIY.
Here's a very in-depth description (you only need the "Electronics Part 1" portion of the post for most scenarios: bax.comlab.uni-rostock.de/en/hardware/amiga500/kickstart-eprom/
@@JanBeta Thank you ☺I did it and it's working🙂
@aki_128 Happy to help! 😃
Very interesting, thank you very much❤!
My bad. It was the resistor. Who would have known. 😁 I really thought it was the Gary.
Hallo Jan. Wie immer ein Klasse Video! :) Ich hätte da eine Frage an dich, was bevorzugst du um die meist sehr staubigen Platinen von alten Computer zu reinigen? Ich sehe das du da mit der Bürste und Alkohol drüber gehst. Machst du das mit der kompletten Platine? Zumindest auf dem Video wirkt diese nämlich super sauber als hätte sie vorher ein Schaumbad genommen :) ...
Bei den meisten Platinen reicht Alkohol und eine Bürste. Staub puste ich meistens mit Druckluft vorher weg. Bei hartnäckigen Fällen benutze ich Wasser und Spüli (siehe z.B. meine „Saved from the Flood“-Videos). Wenn du danach ordentlich mit Alkohol spülst, überleben diese älteren Platinen das sehr gut. Commodore selbst haben nach Zeitzeugenaussagen Spülmaschinen benutzt, um ihre Prototypen zu reinigen in den 80ern. 😅
@@JanBeta Na da wird meine Frau aber Augen machen wenn ich demnächst Platinen neben das Geschirr stelle :D ... Danke für die Info :)
Watching it Picture in Picture as i type this. It's zo Zen for me, and no boubt your going to save the system. :)
I am at 4:11 at this point. My first thoughts, without knowing could be one of the following three....
Fat agnus, agnus socket or gary. I lean 60 percent to gary at this point.
Now to see what it will end with.
Nice job, but it just reinforces the old saying, check the voltages first!
Neither my A500 nor my A2000 have any boot issues under normal operation, however, when I use a PiStorm, I get the same yellow screen exactly ONCE when the system is powered on, then it goes on to flash grey, white, Kickstart/HD boot. No idea why it happens, but it's the only time I've seen the yellow screen on an Amiga in person.
Maybe the PiStorm messes up the IRQ timings slightly. It basically takes over the CPU functions completely and probably the timing is pretty difficult to get right. (Merely guessing here!)
Check the voltages, it might be that your power supply is not delivering enough juice at startup. I have a third party power supply and had to turn up the 5 volts because it kept under-powering the Raspberry Pi (which shows up as lightning bolts if you have a display hooked up to the Pi).
Jan, it was a weird comment you did about swapping chips vs using an oscilloscope. Those chips are rare and expensive, your stash is way more pricey than a good enough oscilloscope to debug an Amiga. The educational value of just swapping stuff around until it works is not great. Fixing stuff is interesting because you learn stuff, this is not just about this specific machine working but about: what is an IRQ? How IRQs and sound can be linked? What is the architecture of the Amiga etc...
I would have to do a lot of research to be able to concisely talk about the exact inner workings of the Amiga IRQs. It’s quite complicated and I don’t understand it nearly enough to share my knowledge with the world. Also, you can still buy A500s for under 100€s and the whole chipset for around 50-70€s, even on eBay. A proper DSO is still a lot more pricy than that. Hope that clears up my point a bit.
Great Video! -Mark.
What is the "ODD CIA" inscription on the PCB? Why "odd"?
The CIAs are just labeled like that in the A500. Left one is ODD, right one is EVEN. I think the engineers had loads of fun (and probably some beers) when they came up with the labels. The schematics have some hilarious jokes in them, too.
@@JanBeta And why "FAT AGNUS"? Does "FAT" mean "fat" or it's an abbreviation?
Expecting something complicated and overlook the simpel fixes.
Didn't you check the voltage with the ossciliscope?
I assumed I already did the super simple voltage checks when I worked on this one years ago. Turns out, I didn't. :D
grüße jan...echt super hilfreiches video. hab das ma an meinen alten 500 versucht, der genau diese probleme hatte....hey, der widerstand ist auch durch!...danke für den tipp. PS: zum thema diagnose chip, kann man den irgentwo käuflich erwerben? das würde meine arbeit extrem verkürzen. ich muß immer noch blindfischen, und das dauert! (weist du ja bestimmt...🙂) ...lg, alles gute, ein echt herzliches dankeschön für deine arbeit und nen super herbst dir...dor GrauKappenHippie
Interessant! Hätte nicht gedacht, dass der Widerstand so ein häufiger Fehler ist. Cool, dass du deinen Amiga so auch reparieren konntest! Habe mittlerweile herausgefunden, dass der Widerstand in Wirklichkeit ein 1 Ohm 1/4W ist. Funktioniert auch mit höherem Wert, aber ich werde den nochmal gegen den richtigen austauschen.
Das DiagROM ist Open Source, ich glaube es gibt Anbieter auf eBay und einige von den größeren Amiga-Versandhändlern haben die auch im Angebot. Ich brenne mir die regelmäßig selbst. :)
@@JanBeta hallo, danke für die antwort. ich hatte in den ami zusammen 4 tage investiert und hab den fehler nicht gefunden...tja, einmal deinen clip schauen, nachmessen und schon funzt es..! 🙂... eine frage noch zu zum brennen. ich hab noch nen eprombrenner für den amiga. kann man das auch mit diesem system realisieren oder hilft da nur n neukauf für nen pc?..lg,weiterso und ich bedanke mich herzlich...🙂
@KrautRockt Wahrscheinlich schafft der Amiga-Brenner noch keine EPROMs in der Größe, die du brauchst. Das DiagROM braucht ein 27C400 EPROM. Um das zu brennen, braucht sogar schon mein moderner TL866 einen speziellen Adapter (einfach weil der Sockel am Brenner physisch zu klein ist für 40-Pin Chips).
@@JanBeta alles klar, danke für die infos...! (bin nicht die hellste kerze was brennen von eproms angeht..🙂...schöne zeit dir!
38:32 Er, I think of you as a fancy--or at least OG--UA-camr. :)
Thank you, Jan. Always great content. 👍
Schematics say it should be 1kOhms for your board revision. But as long as you do not produce a short circuit it should be fine ;-)
Double checked on another rev 5 A500 and it is a 1 Ohm in reality. Very much the same current limiting/fusable resistor that I had to replace in the previous rev 3 repair.
@@JanBeta Ok. Good to know
So what happened is Gary caught Paula cheating on him with Agnes and quit paying her bills and now she has no power.
NOICE!
Were the Amiga 500 CIA's different than the C=64?
They are very similar. As far as I know, the main differences are maximum speed and the missing TOD clock in the Amiga CIAs compared to the 6526s. I heard that you can even use Amiga CIAs in the C64 to some extent but I've never actually tried it myself.
no youre skills are better than m ine and youre video was good
But how does a resistor go bad?🤨
I guess it saw too much current at some point. I said in the video that maybe I plugged a Paula into the socket while the power was on or something. I've also seen resistors just randomly die of old age, although that rarely happens, it does sometimes.
@@JanBetaInteresting, I've seen resistors toasted crispy brown and they still worked. Maybe a manufacturing defect.
Brown black gold is 1 ohm, not 2. RED black gold would be 2 ohm. No wonder the voltage is only 4.7V with a 2.2ohm. It needs to be 1 ohm.
Yup, check my pinned comment.
What an interesting and enjoyable video. A good lesson in troubleshooting: if at first you don’t succeed, put it aside for a bit and come back later, if possible. Often when you come back after a bit you can attack the problem with a fresh perspective and renewed enthusiasm. I’ve got similar issues with one of my Amigas, now I think it’s time to revisit it. Well done Jan!
A good lesson in troubleshooting would have been to start with rule #1: thou shalt measure voltages ... but that would have been a boring video I guess 🙂
I think more people have "fancy oscilloscope" than spare obsolete chips ;-)
Maybe!
Another Amiga saved \o/ Fascinating to watch you work out the issues and how to fix them.
Great repair and very enjoyable video as always! Regarding the new resistor, I think you put a 1/4W there, and I think the original was 1W. Anyway, the lower wattage may cause that resistor to burn out eventually. It depends on the current consumption of the Paula.
I double checked on another rev 5 Amiga 500 and the resistor seems to be a 1 ohm 1/4W in reality. Pretty much the same as the one I replaced on the Rev 3 Amiga previously. Probably used for current limiting or as a fusable resistor for the Vcc (which somewhat makes sense). Thanks!
Great video Jan, what an interesting failure. Congratulations on another successful repair.
Great repair, Jan! Does that CPU Socket problem also apply to an Atari STE? Its has the same socket..and i guess also CPU...
You mean the Agnus PLCC socket, I presume? The sockets Commodore used were just really low quality so they fail frequently, I’m not sure if Atari used similar shoddy sockets. If they are marginally better quality ones, they are going to be way more reliable.
The first step to finding the error is always to measure the voltages on the ICs.
This can be done with any multimeter and is easy.
The second step is to check the reset pulse.
This can be checked with a resistor and an LED without complicated measuring equipment.
Very true! The thing is, I was so sure that I did the basic testing when I first tried to fix this one that it didn't even cross my mind to check voltages again. :D Apparently, I very likely forgot to do that the first time around, too. Didn't really have to probe the reset really in this particular case because the processor was clearly starting up fine.
also, don't forget to check for shorts, especially under those sockets.
Quality job :) Tho' it always amuses me to see the Insert Workbench Logo is painfully left handed which would always the single most uncomfortable way to insert a disc on the Amiga 500 considering the drive is on the right.
The artist responsible for that graphic was right-handed and needed a reference - so she used her left hand.
i think the resistor is 1ohm (brown black gold). 2ohm is strange value for 5% resistor. seems not to be a critical value.
Yes, it’s indeed a 1 ohm. I double checked on another rev 5 board in the meantime.
Im curious, commodore 64 was something I never got into , what does POKE 53281,0 do?
oh, and there is NO SUCH THING as LED blink codes. I have no idea who started this one, but it's completely *false*. The number of blinks is always the same and its just what the fault routines always do. The only thing that means anything is the screen colour.
In this case, with a dead Paula, it could well be that spurious IRQ's happen... this would trigger a yellow screen as it's an unexpected interrupt. 1.3 probably disables interrupts early on in the 68000 (using the SR register in the processor) in addition to using the custom chip INTENA register.
The freeze at the white screen in 1.3 is the system waiting for an interrupt to happen (it's how multitasking is driven), and because Paula is dead, it never happens.
Great job Jan. Thankx for sharing with us. We waiting on your next video. Greetings from Steven from the Netherlands
Loved your expression of joy at 37:04, made it all worthwhile!!! Good fix!
So "einfach" kann's manchmal sein! 😜
Schöne Grüße, Doktor64!
PLCC is 84 pin.
Yes! Thank you! 😊
@@JanBeta Sorry, couldn't resist. Also, could I ask you what is a good source of DRAM for an Atari 800XL? I have one that turns on with a green screen and wanted to start with the memory. All chips on bord are socketed so that would be the easy first step. It has Hitachi 4864-2 DRAM's in it now.
Great stuff.
Finally! ❤
Just yesterday I returned from this year’s 4 day DoReCo party. Had my Amiga (Rev 8a) with me that would suddenly give me all sorts of color codes. First green, then red and then also yellow. Big „Oh no“ moment right there. Note: the machine had worked flawlessly just before going there. After testing a whole bunch of things from loose connections to dirt (everything was spotless) and a lot of head scratching and cursing, the issue turned out to be flux residue on the RAM expander (the Max Plain 512k one).
So contrary to popular belief, sometimes alcohol is indeed a viable solution. 😅
Wow, that sounds like a lot of fun. Glad you figured it out in the end! :D
@@JanBetaDefinitely was tons of fun. But just as in your case, somehow the most puzzling issues have the dumbest solutions 😂
@@DeputatKaktus a healthy dose of isopropanol in your case, eh? :)
@@oidadesgibtsned Yes. And then some good old fashioned ethanol for…celebratory reasons. 🤪👉🍺
A PLCC chip will only fit in the socket one way. One corner of the chip and socket are shaped differently. If the socket is rotated 90 degrees when installed, you won't be able to put the chip in correctly.
I think that’s true for some PLCC packages but not for this particular 84 pin version. You even have to rotate the Agnus if you use a different version for chip mem mods in the A500. This one doesn’t have any physical indentations on the chip side, just a pin one marker.
Great job! I figured the resistor would have been completely open or in the Megohm (which it was) and the 2k reading was because it was still in circuit. Was fun to watch.
"Promosm"
2nd like!
Haha, thanks, you should watch the video and see if you really like it now! :D
@@JanBeta The video has Jan and an Amiga in it! That means we can just turn up, like it, and we don't need to watch to check...
@@davidlloyd1526 Yup, just in theory, as it's a pleasure to watch!
DEFINITELY 1 OHM DRY JOINTS CLEAN ALL IC
SOCKETS 😊😊😊😊
Yup, it’s a 1 ohm in reality. I mistook the brown stripe for a red one. Just double checked on another A500!
Well done indeed, Jan. I love trail by error fault finding and got to say that A500 is one clean looking motherboard indeed.
This made me feel I really have to fix my amigas. Just don't know where to start.
From this repair, I learned to start with the basics, like checking the voltage supply to the chips. Then you could see if the reset circuit work, if the processor clock is there (if you have access to an oscilloscope, that is). DiagROM is also a huge help, even if it’s not very well documented. It at least can help narrowing down the fault most of the time.
@@JanBeta Thing is, I made a stupid mistake when I was gonna upgrade kick 2.0 to 3.1 on my rev 5 500. (Don't do soldering when your blood sugar is to low :P)
I don't know if I killed the PSU (meanwell) or if something else happened but the power led only flashes once quickly when I put the power on, it's completely dead otherwise.
I love that such a long-term problem is fixed right in front of us.!
4.75 Volts is only 5% low anyway, well within limits. Usually when resistors fail it is very obvious! Smell is a surprisingly good diagnostic tool in electronics.
4.75 is right on the edge of the functional voltage range of most 5V 74 series logic
Great video, Jan! As for resistor colors: The only way I can remember them, even after over 45 years playing with electronics is this:
Bad - Black
Beer-Brown
Rots-Red
Our-Orange
Young-Yellow
Guts-Green
But-Blue
Vodka-Violet
Goes-Gray
Well-White
Have fun! 😅
This is the exact phrase I was taught as an electrician in the Navy. Was going to comment but you beat me to it. ;)
Haha, maybe this actually finally helps me remember! 🍻
@@JanBeta For my complicated ways of memorizing stuff, the numbers 2 to 7 are a neat spectrum form red-orange-yellow-green-blue-violet ... brown is not yet properly glowing red so it's 1, black isn't glowing at all so it's 0. Grey is a less bright shade of white, and white is the hottest so they're 8 and 9.
G for grey actually? IIRC gold and silver occur outside the tolerance band only as negative powers of ten. But I might be wrong - wouldn't be the first time and won't be the last.
@@jussikuusela7345 - I believe you are correct. I stand corrected. I jumped the EIA color code and missed the Grey/Gray standard coloring! I corrected the error. Thanks!
Ein „Jan-Beta-Tag“ ist immer ein guter Tag 😊
Und wie!
@roheinz5007 So guten jan-beta-tag.
Another thing to watch out for are those pesky hidden solder bridges - especially under sockets like the one for the SuperPLA on a C64 assy 250469 - any revision, for they all have that big fat SuperPLA. managed to get a solder bridge like mentioned before and boy, what a Hunt that has been. I changed and socketed all the ICs, even the small ones (and good it been, for there have been broken 4066s), but the main culprit has shorted a five-volt line with address line 0 on the superpla (pin 31 + 32 IIRC) - How to find that out? Well, the whole time the machine has shown a weird double addressing stuff, so I knew it had to be something in that vein. On the scope the traffic was depicted with weird shadows and odd traces not adding up to anything making sense. So I asked: Is it possible that there is a short between lines? And then I went and checked the SuperPLA Pins and 'lo! looksie looksie! I 've found what I been lookin' for. Take that, Bono! After a bit of wondering where the hell that short could be, I ve desoldered the SuperPLA Socket, and there, between the two pads, I've found the solder bridge. Removed it, put everything back together and the machine started to work like a charm. :)
So, that was the long story of little me and the big bad SuperPLA - I hope you've found it elucidating in some way, the same as I find Jan's vids both entertaining and informative.
Wow, those faults are difficult to catch! Glad you found it in the end!
To make the circuit more reliable, install a resistor with a slightly lower resistance (e. g. 1.5 Ω) and with a higher power rating (0.5 W), it should fit that size.
No. The resistor is there to help prevent noise from the logic ICs getting to and from the sensitive stuff like Paula but it's also there as a fuse of sorts so increasing the power rating of the part could end up being dangerous in the event of a short on one of the user ports.
Plus, how reliable would you like it to be? It's in a 30+ year old machine
That resistor is not working alone. It is the part of the R/C filter there, value is critical.
@@borayurt66 In this case install the same value, but with a higher power rating.
"Thou shalt always check the voltages first!" 🙂You can just solder a 22 ohms resistor in parallel to that 2.2 ohms and get 2 ohms exactly. Solder it under the board to keep the good looks intact 🙂
DO YOU HAVE A NORMAL JOB JAN 😊😊😊