I honestly like the lighting in the Adrian After Dark videos. It feels more like chatting over a drink and sets the visuals apart from every other retro tech channel out there.
Always satisfying to find the problem and get a board working again. I was surprised the motherboard wasn't tested without the RAM expansion board as one of the first diagnostic steps.
For calcium stains (that's what hard water stains are), a mild acid works fine, just as with kitchenware. Citric acid is commonplace and sold as powder, so you can mix that up to the concentrate level you want.
Brilliant deduction about the mouse button, very impressive! When you first talked about the vertical lines, I was hoping you'd use their exact positioning to help you narrow down the failing RAM chip and sure enough, that's what ended up happening. It's so interesting seeing how close to the metal these older systems are where you can have a 1:1 correspondence between a hardware failure and the actual symptoms, rather than just the random crashing you get nowadays due to all the layers of abstraction between the user interfaces and the hardware itself.
This was a great video, it was amazing watching you go through everything! I have almost no experience with Macs, and I certainly didn't work on them. My elementary school had Apple computers, and got a suite of Macs donated to them shortly before I left. It's always neat seeing the insides of all these computers I was aware of, but never got to truly experience. ^_^
I would've thought removing the ram expansion and restoring the motherboard to stock would've been one of the first troubleshooting steps. After documenting how the expansion was set up, of course.
Great Episode. I never ran across that card while supporting the 68000 Macs but I do remember that RAM errors were always annoying as heck on those, which is why any RAM error got you a spares replacement board and your board went to Apple for repair ( it was faster thus cheaper ). I also remenber how I became the only shop tech who could work on Macintoshes. Now to preface this, my father was and E.E. and actually has a very cool patent from the 60s that is a way to get 8 phone calls over a single radio channel, kind of a tdma sort of thing, and my Dad usually ran a TV repair shop, and so, I kinda grew up those. So I'm trying to do a live power supply/display adjustment on a mac 68000 which means I've a mirror on the bench, and I'm reaching into the Mac to set the gain or whatever it was that made them bloom, and I keep getting tickled now and again by the high voltage, and I softly say "damn" each time, somehow that makes it not hurt. The shop manager, call him Ed, goes "What's wrong" and I tell him "I'm adjusting the gain and I keep getting zapped, and I twitch and miss the setting when I get zapped". Ed gives me this look, like I'm some kind of imbecile that must be pittied, and says " I'll do that " and takes over. Oh Right, the customer was there waiting to pick the Mac up, and the screen was over bright and not too readable, that's what the isuse was, lolz , memories, like holograms, the more you excerise the memory, the more of it pops back. So I go up to tell the customer "Just a few more minutes, the service manager is taking care of the adjustment" and walk back to the shop, when Ed screams "Fuck" and I see the Mac come flying across the shop, hitting something and the CRT goes "POP" Ed claimed he got shocked, spasmed and the Mac took flight. But because I'd worked on CRT TVs so much, I didn't (still don't) have the same reaction to getting shocked as most people, stun guns can make me laugh, and I can walk while being tased, not easily, but yeah, that's how the verry irritated Computerland GM declared that unless anyone else had high voltage experience I should be the only one working on CRTs. Oh yeah, the Custome ended up with a whole new Mac too. Lolz, I later built a jig with extended cables to let you safely do those adjustments.
Thanks, Adrian. The After Dark segment has one of the BEST explanations I've ever seen about the dance between hardware and software in these early Macs (and even a bonus dive into 68K ASM!) Excellent, informative and riveting video. A Master Class in information-led diagnostics. ❤
Watching this from Gresham... Love the repair videos and the logical deduction and creative solutions to find them. Keep up the repair videos and enthusiasm. It's very infectious.
Just excellent logic and work! One of your best videos of all time! I don't care about MACs at all we never had them here in Greece, but I loved the way you approached the situation and even without a scope's help which is a tool most of us don't have, you figured out the fault! Cheers, keep up the great work, Jim.
1:00:10 you've could just count pixels between your line and line that motherboard RAM generates, and removed the chip that lives needed count of bits away.
This was one of my top favourite videos of yours. Maybe the top video due to your tenacity to troubleshoot it until you got it working. Over the years I have lost sleep not being able to solve a problem. I once took 2 months back in 2006 with technicians in both the US and Canada helping to try and solve a problem that seemed to have no solution. Then one night at 3am a thought popped into my head so I hoped in my truck and drove to my customers sight to try my fix and bingo it worked. It’s very satisfying fixing a problem like that.
The “water stain” is quite likely calcium carbonate. As somebody else already noted, vinegar would dissolve it, IF you can tolerate the smell. If not, maybe you could find oxalic acid that will do the same with radically less odor. After the acid treatment (just a couple minutes), you should put the board through a dish washer cycle, and after that, flush twice generously with distilled water, followed by blow drying. Mildly warm, if you can produce such. A good long time!
Love your videos, Adrian! Great detective work discovering that mouse-button disable feature for the RAM card. I got very similar jailbar video artefacts while trying to restore my old family IIsi - in 1-bit video mode I noticed the pattern of black bars repeated every 32 pixels (the data bus width of that machine). Looking at the jailbar pattern on your Sad Mac (a 32x32 icon centered on a 512 pixel wide frame buffer), if you count down from 15 starting from on the left side of the icon, you'll find the bar coincides with bit 10 where the first black bar on the left appears. This technique helped me home in on a capacitor-eaten data trace between RAM and the video IC on my machine.
Great job Adrian! It seems like a weird design choice that holding down the mouse button doesn't make it use the mobo RAM, but rather the first bank on the card.
Very good episode, Adrian. Hope you weren't _too_ wired at stupid-o'clock in the morning when you'd completed the repair and were able to get a good sleep after that :) Certainly an intriguing fault given the unknown RAM boards and patina of limescale on the motherboard.
I fixed some single pixel vertical bars like that on one of my SE/30. Just needed to repair a couple broken traces. Thanks for the explanation Adrian! I love following along with your repairs.
This was an awesome episode. Loved watching the thought process lead to that solution. My hat is off to you... as long as the east wind isn't blowing in from the gorge.
Great video, Adrian! I like the after dark theme. What really caught my eye was the video ports on the SE in the beginning. I have a SE with similar ports, it has a video card made by Orchid Technology. I have never gotten the card to work. Either I’m missing a driver or the card is bad.
Hi, another great work! Recently i learned some ram debugging trick: wire method. One end of wire connected to gnd or 5v, and with other end you can pull down or up data lines of ram chips (for short time, not to damage chip) and look for vertical line
Yup, I was going to say this. To be safe you probably want to use something like a 10 ohm resistor instead of a wire, then if you short the power rails you shouldn't fry anything.
Yet another excellent video from one of my favorite UA-cam creators (right up there with David at Usagi Electric and Ben Eater). Some of the mail call and similar videos may not get a full watch, but the deep dive ones like this are always worth the watch. Great start to a week vacation, and I even heard Adrian use my comment from his last after dark video in this one. :)
Do you have a program that can now test all of the other ram on the expansion board, other than that first bank that we know works? PS: I loved the entire deep dive and technical knowledge you have now bestowed on the world. I was following right along with you, talking to the screen about the different data lines and then you would mentioned them. So cool to see someone tear into these old PCs with your experience level. Thank you!
One of the best episodes to date! I always admire IPL or boot sequences for different platforms. I wish someone explained the power-on procedure for later macbooks, like the pro from fall 2009.
Keep the faith. You do what they all said couldn't be done. Board level repair. Those fatalists. We can't let them win. Thanks for the content. Keep up the good work. בס'ד
Growing up with serial and USB mice, I always thought of them as something complex for later in the boot process when you'd gotten things running. It never occurred to me that the mouse button on its own might wind up as a TTL signal on the motherboard, but in retrospect given it was a huge part of the Mac, it's a pretty sensible way to do it.
The only thing I find questionable myself is the crystal with using CLR. If that can is not completely sealed at the base and any liquid gets in there it's done. Maybe desolder it. Idk if i would even bother though. A lot of work for it to just look nice.
I am wondering if you can just override the Q output of a DRAM with a wire connected to a pull-up or pull-down resistor and see which column of pixel changes on screen.
Can confirm this trick works on most old arcade boards and makes troubleshooting much easier. EDIT: I usually short to ground. (TL;DR most chips aren't damaged by shorting the output to ground. They will be damaged by shorting to +5V though. If the output driver is bad, you can control the outputs with a resistor, but if the internal logic is bad, if the output is stuck at GND, it will override anything above like 10 Ohms, and if it's stuck high, the other chips need the LOW signal to be below .8V and for some reason you need two-digit Ohms for that too.)
After watching this video I seem to remember doing the mouse button trick back in HS in the 90s on a Mac Classic that was acting up in class. Doing that made the machine slow but eliminated the crashes. A teenage me (who was only into PCs at the time) didn't bother to wonder why it worked, just that it did.
This Episode of After Dark is so spicy it needs an Only Adrian account. 🤪 Seriously though, I really enjoyed the way you backed off and walked us through the thought process to understanding how this particular RAM card design played with the motherboard and the errors you saw. Well done!
Hi Before moving on to CLR to clean the motherboard to remove the water stain, I suggest trying citric acid AKA lemon acid (mild organic acid used in many cleaning products) If it's not good, I would try the acetic acid AKA vinegar (also used in cleaning product)
I noticed in this video (it might happen more often) that you might not be tinning the pins when you desolder with the hakko, as compared to your old unit. Does it just "work" most of the time without adding solder before desoldering? What about the heat gun when you remove chips/sockets on the top side?
Yeah I almost never add solder when removing a chip. Only if there is a pin that I botched and need to go again. Hot air isn't always needed depending on how clean the desoldering is. Not sure why some boards are easier than others -- maybe larger holes? The sockets melt with hot air so I don't usually use it.
As a (former) digital design engineer, having the high bank of RAM on the motherboard makes sense; the video is more likely to work, and it should have just a touch lower latency. (Tho at these clock speeds, it isn't a visible difference.) Of course, hindsight is 20/20...
I wonder if it also removed the need to route the DQ lines from the expansion card to the video and sound shift registers (by leaving them on the main board).
I have a IIci logic board that had a black background on the on-board video at boot. Turns out the Bt478 RAMDAC was bad. Once I replaced that chip, the proper background appears at boot. Kinda made me wonder if there’s some rudimentary video subsystem diagnostic in the ROM and it sets the background black if it detects an error.
I'd likely need help as I'm no good at 68000 assembly. It would be pretty easy though if I had someone to help as yeah I learned the structure of the memory map now.
If I want a 286 laptop with DIP IC RAM to have more RAM, and bigger capacity ICs are not available, what should I do? Currently it has 1MB but I would like it to have 2MB RAM instead. It has 9x4 RAM ICs inside.
This whole troubleshoot reminds me of the "which cup has the Iocain poison" logic loop from the Princess Bride. "Parallel Pirates from Alameda don't like corrosion and will keep it as far as possible from them, therefore, I clearly cannot trust the RAM chip in front of me..."
The fact the line was 6 pixels over would have pointed you to data line 5 or 10 I think. The fact it was 10 suggests that the video is read from 15 down to 0 across each 16 pixel block
![Adrian's Digital Basement ][](http://yt3.ggpht.com/ytc/AIdro_k7CrQRe71qN6c0Ua7A1P_I8KkxjqLa70u0zYeCvdvnKw=s48-c-k-c0x00ffffff-no-rj)
I honestly like the lighting in the Adrian After Dark videos. It feels more like chatting over a drink and sets the visuals apart from every other retro tech channel out there.
Screen looks more comfortable if not for circuit reading or detail.
Agreed! I really enjoyed the after dark ambiance. I definitely hope there are more of these to come!
This guy never ceases to blow my mind with his diagnostic skills
Holy sh*t, all that explanation and schematics reading lead to "I'll just hold the mouse button..." and the system boots :D
If this were the 1980s it'd be an RTFM moment, but... Nearly 40 years later and the manual is lost to time...
I like the Adrian after dark. It has a cool feel with the mood lighting.
Like hanging out with your buddy in a bar or tavern.
I was just thinking the same thing. Just a couple buddies shooting the shit about computers that they’re fixing. I dig it!
Always satisfying to find the problem and get a board working again. I was surprised the motherboard wasn't tested without the RAM expansion board as one of the first diagnostic steps.
I keep thinking Adrian needs a Flying Toaster plushy for the after dark sessions. It could be friends with Rammy.
@@logipilotJust a quick tip: It’s you’re, not you’r.
I like the after dark format. Do more please. Thanks!
For calcium stains (that's what hard water stains are), a mild acid works fine, just as with kitchenware. Citric acid is commonplace and sold as powder, so you can mix that up to the concentrate level you want.
When i was a programmer, i got my best work done between the hours of 1am and 3am. Quiet, no interruptions from the world, it was perfect for coding.
Brilliant deduction about the mouse button, very impressive!
When you first talked about the vertical lines, I was hoping you'd use their exact positioning to help you narrow down the failing RAM chip and sure enough, that's what ended up happening. It's so interesting seeing how close to the metal these older systems are where you can have a 1:1 correspondence between a hardware failure and the actual symptoms, rather than just the random crashing you get nowadays due to all the layers of abstraction between the user interfaces and the hardware itself.
That was a tour de force in troubleshooting an unknown function. Well done!
fantastic fault finding, well done on you persistance too. And I enjoy fault finding too, even after over a 40 year career in electronic engineering!
This was a great video, it was amazing watching you go through everything! I have almost no experience with Macs, and I certainly didn't work on them. My elementary school had Apple computers, and got a suite of Macs donated to them shortly before I left. It's always neat seeing the insides of all these computers I was aware of, but never got to truly experience. ^_^
I would've thought removing the ram expansion and restoring the motherboard to stock would've been one of the first troubleshooting steps. After documenting how the expansion was set up, of course.
Your level of research, attention to detail and layperson explanation is AWESOME!
Great Episode. I never ran across that card while supporting the 68000 Macs but I do remember that RAM errors were always annoying as heck on those, which is why any RAM error got you a spares replacement board and your board went to Apple for repair ( it was faster thus cheaper ).
I also remenber how I became the only shop tech who could work on Macintoshes.
Now to preface this, my father was and E.E. and actually has a very cool patent from the 60s that is a way to get 8 phone calls over a single radio channel, kind of a tdma sort of thing, and my Dad usually ran a TV repair shop, and so, I kinda grew up those.
So I'm trying to do a live power supply/display adjustment on a mac 68000 which means I've a mirror on the bench, and I'm reaching into the Mac to set the gain or whatever it was that made them bloom, and I keep getting tickled now and again by the high voltage, and I softly say "damn" each time, somehow that makes it not hurt.
The shop manager, call him Ed, goes "What's wrong" and I tell him "I'm adjusting the gain and I keep getting zapped, and I twitch and miss the setting when I get zapped".
Ed gives me this look, like I'm some kind of imbecile that must be pittied, and says " I'll do that " and takes over.
Oh Right, the customer was there waiting to pick the Mac up, and the screen was over bright and not too readable, that's what the isuse was, lolz , memories, like holograms, the more you excerise the memory, the more of it pops back.
So I go up to tell the customer "Just a few more minutes, the service manager is taking care of the adjustment" and walk back to the shop, when Ed screams "Fuck" and I see the Mac come flying across the shop, hitting something and the CRT goes "POP"
Ed claimed he got shocked, spasmed and the Mac took flight.
But because I'd worked on CRT TVs so much, I didn't (still don't) have the same reaction to getting shocked as most people, stun guns can make me laugh, and I can walk while being tased, not easily, but yeah, that's how the verry irritated Computerland GM declared that unless anyone else had high voltage experience I should be the only one working on CRTs.
Oh yeah, the Custome ended up with a whole new Mac too.
Lolz, I later built a jig with extended cables to let you safely do those adjustments.
Isn't is such a great feeling of accomplishment when you find the code that figures out the bad chip? So good!
Amazing skills Adrian! The second channel really deserves more contend like this one. Congratulations!
Thanks, Adrian. The After Dark segment has one of the BEST explanations I've ever seen about the dance between hardware and software in these early Macs (and even a bonus dive into 68K ASM!) Excellent, informative and riveting video. A Master Class in information-led diagnostics. ❤
Watching this from Gresham... Love the repair videos and the logical deduction and creative solutions to find them. Keep up the repair videos and enthusiasm. It's very infectious.
Just excellent logic and work! One of your best videos of all time! I don't care about MACs at all we never had them here in Greece, but I loved the way you approached the situation and even without a scope's help which is a tool most of us don't have, you figured out the fault!
Cheers, keep up the great work, Jim.
1:00:10 you've could just count pixels between your line and line that motherboard RAM generates, and removed the chip that lives needed count of bits away.
This was one of my top favourite videos of yours. Maybe the top video due to your tenacity to troubleshoot it until you got it working. Over the years I have lost sleep not being able to solve a problem. I once took 2 months back in 2006 with technicians in both the US and Canada helping to try and solve a problem that seemed to have no solution. Then one night at 3am a thought popped into my head so I hoped in my truck and drove to my customers sight to try my fix and bingo it worked. It’s very satisfying fixing a problem like that.
I like After Dark, and I love the old screensaver too.
I really enjoyed this video. I also like the Adrian After Dark video format.
Dang, great work! I love how you found the (well lack of) RAM test stuff in the ROM and the mouse down workaround for the add-in card
What an amazing 'whodunnit' bit of RAM detective work! I loved watching you finding the culprit.
The “water stain” is quite likely calcium carbonate. As somebody else already noted, vinegar would dissolve it, IF you can tolerate the smell. If not, maybe you could find oxalic acid that will do the same with radically less odor. After the acid treatment (just a couple minutes), you should put the board through a dish washer cycle, and after that, flush twice generously with distilled water, followed by blow drying. Mildly warm, if you can produce such. A good long time!
Citric acid can be used as well.
Love your videos, Adrian! Great detective work discovering that mouse-button disable feature for the RAM card. I got very similar jailbar video artefacts while trying to restore my old family IIsi - in 1-bit video mode I noticed the pattern of black bars repeated every 32 pixels (the data bus width of that machine). Looking at the jailbar pattern on your Sad Mac (a 32x32 icon centered on a 512 pixel wide frame buffer), if you count down from 15 starting from on the left side of the icon, you'll find the bar coincides with bit 10 where the first black bar on the left appears. This technique helped me home in on a capacitor-eaten data trace between RAM and the video IC on my machine.
Amazing work… great detective work.
I’m so glad that someone like you is rescuing these vintage machines!
Wow, that was crazy! Great Job! Thank you for sharing with us and the explanation! ❤
I love watching you problem solve your way through all of these repairs! It's so satisfying!
Great job Adrian! It seems like a weird design choice that holding down the mouse button doesn't make it use the mobo RAM, but rather the first bank on the card.
Very good episode, Adrian. Hope you weren't _too_ wired at stupid-o'clock in the morning when you'd completed the repair and were able to get a good sleep after that :)
Certainly an intriguing fault given the unknown RAM boards and patina of limescale on the motherboard.
I fixed some single pixel vertical bars like that on one of my SE/30. Just needed to repair a couple broken traces. Thanks for the explanation Adrian! I love following along with your repairs.
This was an awesome episode. Loved watching the thought process lead to that solution. My hat is off to you... as long as the east wind isn't blowing in from the gorge.
Great video, Adrian! I like the after dark theme. What really caught my eye was the video ports on the SE in the beginning. I have a SE with similar ports, it has a video card made by Orchid Technology. I have never gotten the card to work. Either I’m missing a driver or the card is bad.
Hi, another great work! Recently i learned some ram debugging trick: wire method. One end of wire connected to gnd or 5v, and with other end you can pull down or up data lines of ram chips (for short time, not to damage chip) and look for vertical line
Yup, I was going to say this. To be safe you probably want to use something like a 10 ohm resistor instead of a wire, then if you short the power rails you shouldn't fry anything.
I sometimes wonder if the board designers watch this program and sit there laughing as you struggle to understand their work?
I had left Steve Wozniak a message a fair while ago to have them pop in once in a while to watch.
@@llwellyncuhfwarthenI don't think Woz worked on the Macintosh.
@@Toonrick12 Adrian has done Apple II diag/repair work. Woz would recognize some of that..
Yet another excellent video from one of my favorite UA-cam creators (right up there with David at Usagi Electric and Ben Eater). Some of the mail call and similar videos may not get a full watch, but the deep dive ones like this are always worth the watch. Great start to a week vacation, and I even heard Adrian use my comment from his last after dark video in this one. :)
Ok, figuring that out about the mouse button really makes you look like a friggen genius, Adrian.
Love the after dark content!
I really love the 'after dark' vibe. I also enjoyed watching the chess game at the end.
Love the deep dive fault finding and the video format. Feel free to keep them going.
Do you have a program that can now test all of the other ram on the expansion board, other than that first bank that we know works?
PS: I loved the entire deep dive and technical knowledge you have now bestowed on the world. I was following right along with you, talking to the screen about the different data lines and then you would mentioned them. So cool to see someone tear into these old PCs with your experience level. Thank you!
I really enjoyed the troubleshooting in this video. The repair videos are definitely my favorite.
Simply amazing. Love this kind of content. Thanks!
One of the best episodes to date! I always admire IPL or boot sequences for different platforms.
I wish someone explained the power-on procedure for later macbooks, like the pro from fall 2009.
As always, Adrian, excellent video. And again, we learned so much. Thank You!
Awesome totally cool and well done, love your thought process with this problem.
Keep the faith. You do what they all said couldn't be done. Board level repair. Those fatalists. We can't let them win.
Thanks for the content.
Keep up the good work.
בס'ד
59:13 That beep was obviously a different pitch. Probably a good indicator of something corrupt as the beep routine is assembly code that runs.
Thanks!
You're welcome! Appreciate the support!
This was the fastest moving video you have made. Adrian, how much caffeine to stay up to do this? Fun all the same. Great deductions.
Growing up with serial and USB mice, I always thought of them as something complex for later in the boot process when you'd gotten things running. It never occurred to me that the mouse button on its own might wind up as a TTL signal on the motherboard, but in retrospect given it was a huge part of the Mac, it's a pretty sensible way to do it.
Adrian you amaze me and your detective work is great. I like the after dark sessions. I look forward to your videos on Wednesday’s and Saturday
I really enjoy watching your content in general, this one however was just one of the cherry on the top ones!
The only thing I find questionable myself is the crystal with using CLR. If that can is not completely sealed at the base and any liquid gets in there it's done. Maybe desolder it. Idk if i would even bother though. A lot of work for it to just look nice.
I am wondering if you can just override the Q output of a DRAM with a wire connected to a pull-up or pull-down resistor and see which column of pixel changes on screen.
Can confirm this trick works on most old arcade boards and makes troubleshooting much easier.
EDIT: I usually short to ground.
(TL;DR most chips aren't damaged by shorting the output to ground. They will be damaged by shorting to +5V though. If the output driver is bad, you can control the outputs with a resistor, but if the internal logic is bad, if the output is stuck at GND, it will override anything above like 10 Ohms, and if it's stuck high, the other chips need the LOW signal to be below .8V and for some reason you need two-digit Ohms for that too.)
Super funny and great video! I very much enjoy all the troubleshooting, congrats!!! well done!
Awesome video Adrian, love the after dark stuff - amazing! 😊👍
Vinegar would also work to remove those hard water stands and neutralize any remaining battery juice.
Great job figuring it out Adrian thanks for video
After watching this video I seem to remember doing the mouse button trick back in HS in the 90s on a Mac Classic that was acting up in class. Doing that made the machine slow but eliminated the crashes. A teenage me (who was only into PCs at the time) didn't bother to wonder why it worked, just that it did.
42:55 It's not a mirrored copy of display memory but a direct mapping from masking high address bits, isn't it?
This Episode of After Dark is so spicy it needs an Only Adrian account. 🤪
Seriously though, I really enjoyed the way you backed off and walked us through the thought process to understanding how this particular RAM card design played with the motherboard and the errors you saw. Well done!
Good job mate! Had fun watching.
48:11 holy shit that's magical lol. Crazy you figured that out.
Truly excellent piece of diagnosis
I have to say that going to Adrian's class is quite entertaining. I learned a lot.
Think it's time to create a test kit for mac's... that was a good job figuring out what was going on....
FYI DB-19 connectors are available once again. Amazon has them, for example.
The clear plastic window on the side of the headphone jack comes off if you wanted to clean the contacts
What a tricky knot you untied. That is a job well done! So the only things really wrong here were two ROM chips and a RAM chip?
I had a few SE models myself. Never had a battery explode. I reallyi enjoyed this video. I no long have any MAC systems :(
What an inspiring video, great logic and persistence.
Just notice yours t-shirt ... May the 4th be with You. 😎 .... the force is strong with this One.
Do you ever try to figure out why these chips fail and when?
Amazing work and I learned a lot from this video. Thank you for your detailed research and explanations.
That’s pretty impressive sleuthing to track down that mouse button trick.
Rammy approves of your ram troubleshooting skills Adrian.
I’m really enjoying the after dark series. Definitely want more!
Hi
Before moving on to CLR to clean the motherboard to remove the water stain, I suggest trying citric acid AKA lemon acid (mild organic acid used in many cleaning products)
If it's not good, I would try the acetic acid AKA vinegar (also used in cleaning product)
Thanks for another great video. It really blows my mind how you managed to solved this. I'm really impressed by that!
Thanks!
This was satisfying to watch! Glory!
that was a fun adventure! enjoyed it quite a bit.
I sent you a e-mail on a source for the DB-19 Right Angle Female that is new. Great Video!
I noticed in this video (it might happen more often) that you might not be tinning the pins when you desolder with the hakko, as compared to your old unit. Does it just "work" most of the time without adding solder before desoldering? What about the heat gun when you remove chips/sockets on the top side?
Yeah I almost never add solder when removing a chip. Only if there is a pin that I botched and need to go again. Hot air isn't always needed depending on how clean the desoldering is. Not sure why some boards are easier than others -- maybe larger holes? The sockets melt with hot air so I don't usually use it.
While I am worn out with all the Mac videos, I really enjoyed the finding of the issue. Great job, hope you get a Coleco Adam some day.
As a (former) digital design engineer, having the high bank of RAM on the motherboard makes sense; the video is more likely to work, and it should have just a touch lower latency. (Tho at these clock speeds, it isn't a visible difference.) Of course, hindsight is 20/20...
I wonder if it also removed the need to route the DQ lines from the expansion card to the video and sound shift registers (by leaving them on the main board).
The video works fine from the RAM board. That was how it was running with the mouse button held down. (512k mode)
Good point, the testing you did with many chips removed to find the bad chip rules that out.
I suppose you could've used an oscilloscope on the data pin on the RAM chips and look for the one that was stuck.
I have a IIci logic board that had a black background on the on-board video at boot. Turns out the Bt478 RAMDAC was bad. Once I replaced that chip, the proper background appears at boot.
Kinda made me wonder if there’s some rudimentary video subsystem diagnostic in the ROM and it sets the background black if it detects an error.
Great detective work. Now that you know a bit more, maybe you should write a good RAM test ROM?
I'd likely need help as I'm no good at 68000 assembly. It would be pretty easy though if I had someone to help as yeah I learned the structure of the memory map now.
simply amazing! great work!
If I want a 286 laptop with DIP IC RAM to have more RAM, and bigger capacity ICs are not available, what should I do? Currently it has 1MB but I would like it to have 2MB RAM instead. It has 9x4 RAM ICs inside.
The twists and turns!
This whole troubleshoot reminds me of the "which cup has the Iocain poison" logic loop from the Princess Bride. "Parallel Pirates from Alameda don't like corrosion and will keep it as far as possible from them, therefore, I clearly cannot trust the RAM chip in front of me..."
Great series!
The fact the line was 6 pixels over would have pointed you to data line 5 or 10 I think. The fact it was 10 suggests that the video is read from 15 down to 0 across each 16 pixel block
I noticed that the headphone jack is exactly the same as the atari 2600 power socket I just replaced 3 of them at 5usd each.