The troublesome Mac Classic and Classic II are finally working! (stuck at 512k fix)

[@Laffen47]

"Let's see what happens if we unplug the memory while it's running" A man after my own heart

[@the_kombinator]

I actually did that when I was 12 to a 386 with 30 pin SIMMS. The computer crashed.

[@LewinEdwards]

That wire issue is common on these machines, and it usually only affects some wires in the harness. It's a plasticizer turning into acetic acid. It's not electrolyte wicking down the harness.

[@PaulinesPastimes]

I have even seen this with house wiring from the 1970s. It causes the same green oily goo inside the PVC insulation.

[@stevethepocket]

So is it...actually bad, or just ugly?

[@jwhite5008]

​@@stevethepocket you probably don't want any acid inside your wires it both degrades the wires and insulation the wires will probably work until the corrosion has eaten away the copper completely, but you never actually know the condition of the wire along its length

[@PaulinesPastimes]

@@jwhite5008Sounds like someone has just put up a challenge: How long does it take for the conductor to be degraded by green acid goo. 😄

[@anno250]

I've seen that happen on thick ,fine ,long and short wire I always put it down to faulty manufacturing. I've also seen it happen to mains wire . Its so hard to believe an acid or what ever can travel down the length of an insulated wire. Sometimes its so bad the copper has gone brittle ,nearly always its impossible to solder. Definitely an interesting topic.

[@fluxilla]

this kind of troubleshooting is fantastic to watch. Adrian makes it look so easy! I love the overlaid schematic/scope/board/camera shots too, very nice.

[@ScarletSwordfish]

I think this is the first time I've ever seen someone use the interrupt console for actual troubleshooting, or anything other than typing G to escape a crash. Marvelous work, your detective skills are so exciting to watch.

[@smakfu1375]

The MicroBug machine code monitor was okay, but very basic. But it was MacsBug that was boss. I don’t even like classic MacOS as a piece of system software (all hail the Amiga), but man, MacsBug was (kinda still is) awesome. Install the extension and it wired the NMI for the programmers key to an ISR that fired up the MacsBug debugger (originally developed by Motorola, IIRC). From there you could do all sorts of wonderful things. And yeah, that programmer key was used so much that many of us had case key buttons (that slotted through the ventilation slots) for easy access. Actually, I still have said programmer key kit thing, because my MacSE is still very much alive and kicking, complete with 4MB of RAM and a glorious Radius 68020 accelerator with 68881 FPU - that I installed myself in 1990 after getting it steeply discounted from a computer store liquidation. I got the computer in 89 as a castoff from my father’s office; it was about 2 years old and collecting dust, and a nerd simply doesn’t allow such a computer to just collect dust. I asked if I could have it (I already had an Amiga) and the office manager said “take it”. It had hardly been used, purchased for an employee who left, in an office with a 3+Share LAN and a lot of WordPerfect and Lotus123, so I put it to all kinds of good use (especially after I got that Radius accelerator).

[@jandjrandr]

A monumental job repairing those Mac Classics! I've said it before that those machines are a large part of my senior high school years. I used Classic Macs for computer science class and even helped the teacher upgrade the RAM on the Color Classic II computers back in the day. Thank you for bringing life back into these systems!

[@aleksandrbmelnikov]

One old copy protection was to rollover the memory addresses and store values at an address they knew wasn't valid. That value would move disk heads to a magic number hidden outside file area. Now we have programs that raw-copy everything on a disk.

[@atcmiker]

Well done Adrian, I love the look of joy on your face when you fix stuff. I will admit to not having a clue what you are talking about. But i am addicted to your channel for the last 4 years or so. Thank you..

[@JCHaywire]

Adrian! I can't believe your level of confidence in troubleshooting. Finding no activity on that Pin 5--and being confident enough to swap out the chip. Super impressive, my friend. It's amazing, really. Jonathan in Seattle

[@IkesVintageTech]

So it’s 1am and I should have went to bed and yet again you got me hooked the whole time. What a rollercoaster with that chip. Glad you got everything up and running.

[@FlyMIfYouGotM]

The corrosion issue with the wire was also something very common with old NiCad battery packs. It was very common for the Red lead from a NiCad Battery pack to wick the Potassium Hydroxide electrolyte from the battery into the wire causing the positive wire to fail.

[@whiteyukimi]

The way you analyze the issue is absolutely amazing!!

[@ast3663]

wow, so much info and learning about these vintage macs just from this one video..great Adrian

[@LynxCarpathica]

Fun fact, O2 sensors in cars work the same way, the "reference" air from outside wicks up to the probe body. Therefore you must not solder those cables, but only crimp it.

[@78trav]

I remember the late 90s f150 condensate drain would drip on the wiring and cause a trim code.

[@dariodzimbeg]

I'm soooooo happy when you manage to isolate the problem and fix the machine. The smile on my face... you should see it.

[@mrkrsl_]

Superb systematic troubleshooting skills. Very impressive.

[@PaulinesPastimes]

That was brilliant. I was so excited at the end there when the 74LS174 chip worked, I was clapping my hands with glee. Great result. 😊

[@horusfalcon]

There I was saying to myself, "Adrian, quit screwing around and get out the O-scope!" Ya must have heard me... 😆

[@algorithms-memo104]

52:20 you could also look at the other LS logic chips on the board to see if there's a spare gate.

[@michaelhaardt5988]

That was one of your most brilliant debugging sessions. Congratulations! Very enjoyable. :)

[@zxrenew5642]

Brilliant diagnosis. Thoroughly enjoyed the series. Cheers buddy.

[@cmjones01]

Nice repair job. Very interesting that the bog-standard TTL part was the faulty one. I rescued a Mac SE/30 some years ago which had capacitor leakage, and in that there were about half a dozen 74xx logic parts in the video and memory circuitry which had gone bad and needed replacing. All the big chips and custom stuff were fine, and they still are - the machine still works to this day.

[@ChristopherMcAvaney]

The pure elation at 56:00, love it - so good. Well done Adrian.

[@dotcom624]

Loved the excitement when you finally got the Mac Classic to work! You should make a shirt with “It Freakin’ Works” on it…turns out you do! Excited to rock it when it arrives!

[@CatenationIndustrial]

The fix with the 74LS174 was so satisfying and made me so joyful! Also love the "rude" things with the card and the jumper etc. ;) [Would've loved to see if the spikey weird address lines still looke the same with the replaced chip!]

[@keithstathem872]

The last startup issue you were having with the classic II sounds like a connection that's just a tiny bit loose. The high resistance through the connection heats it up just enough to expand and form a solid connection, so the second or third time you turn it on it works fine - until you turn it off for a couple days and try to use it again, and it starts acting up again. It's a common problem even with brand new systems if you're supercooling the cpu or, as in my case, just don't like to heat the shop in the winter. A thermal camera pointed at the board right when you first turn it on can tell you a lot.

[@nanoatom6146]

When I grow up I want to be as good as you are at electronics. 🙂

[@tom940]

makes me want to revisit my mac plus and classic II. Both had non-standard issues, and atleast the diagrams for the plus leave alot to be desired, at work we call drawings like that "napkin drawings" because we used to have an engineer that would draw stuff on napkins during lunch and hand it off to the boss lol

[@shannonconley2730]

I find it funny that even thought some mother boards say there’s a limit on memory but yet when I add more it still works and still show the correct amount, I think they do that so you upgrade the computer itself

[@dcarlin3]

Great video, I learn a lot watching you go thorugh your troubleshooting process

[@baronvonschnellenstein2811]

Nice work there, Adrian. Glad that the memory addressing fault on the O.G. Classic was with one of the few discrete logic devices that are more easily replaceable :)

[@elfenmagix8173]

You did extremely well with both repairs. On the 68K Macs, removing 12V will "kill it" because 12V is needed for Sound, Floppy & HD, RAM/ROM-GLU Logic, and Video. As for the wire not being internally corroded - simple: they are inc plated copper, as are the end, but the zinc plating it tinner at the connectors and will have some wear exposing the copper. Cap goo would ha travelled though the wire and when it hit the ends, started corrosion there at the exposed copper. Repairable? Yes, but like you did, beter to just replace the wire. Just a proposal; lets say you set up a BBS using those Macs. Problem the video is constantly on which wil cause burn-in and other issues of wearing down the high frequency ares of the video portion. Question is, would putting a switch at the diode that feeds the video circuit to turn it on and off while the Mac is on effect it in any way? Basically set it up to turn on/off the monitor like one would do if the monitor was separate like on a Mac II...? B/W Mac BBSes were a thing but short lived because their video sections would burn out. Thus when the B/W Mac died, they were replaced with something from the Mac II Family. I remember my club starting with a Mac IIci and then moving to a Q700 and then to an PPC8100 and finally to a PPC8600(?) before disbanding in early 2000. One member even had a BBS for his business on an iMac G3, but had some "expert" disconnect the video and CRT tube so that it was always dark and used a remote access program (Timbuktu) to access the machine from afar. (Sorry for the length...) So far the repairs have been easy,, meaning that they wre digital in its fault ad repair,, though they wre difficult to diagnose and repair. But in reading Larry Pina's series of books (You sould get them), a lot of the repairs he shows is repairs of the PSU and Video circuitry, which is you follow his directions are very simple to repair once you had diagnosed the problem. The issue it - where does one get parts for the B/W Mac Video circuits? Many of such parts are no longer being made and what few parts that are available are almost impossible to find and expensive to get. Besides the usual suspects, where would one try to find such parts? Where can one get compatible parts. Back in the 1990s, I had 20 Flyback transformers for the B/W Macs, I am down to my last one and can't find any replacement for it. Another point of failure for 68K Macs is the Bornes Filter at the ADB Port. Removing/adding a keyboard and mouse while the Mac is on usually won't will the Bornes filter. But there is a chance that it will. I'm sure there are dozens of Macs with dead ADB Ports out there, but near zero access to a replacement Bornes Filter Chip. There has to be a way to Hack that back to life somehow....

[@frostwise87]

This is totally fascinating, thanks so much man. Your a great presenter

[@frostwise87]

Ps your are really great at this man, I was very happy to see 1 mb ran :)

[@borislab8153]

really entertaining to watch you repair these dinosaurs

[@telemedic5142]

Great sleuthing! You have come on a long way over the years I have been watching you. Fair play, great videos. Thank you 😊

[@SomeMorganSomewhere]

The "silvery" wires are tinned copper strands, they tend to be more oxidation resistant than copper alone.

[@jstinn123]

I owned a classic ii back in the day. It was slow but made a decent semi portable computer for word processing while traveling.

[@jasmijndekkers]

Adrian you did a great job. Fantastic to see you and joy what you are doing. Great content and nice videos. Greetings from Steven from the Netherlands

[@adamklotblixt2392]

Very solid trouble shooting, always nice to see a pro at work.

[@patriziopolcri995]

Great work Adrian!! Thank you for giving this excellent example of how to find the problem following the schematics..Great! Cheers from Italy

[@cremvustila]

I really enjoyed this series, thank you!

[@fredoralive]

The keyboard reset (cmd-ctrl-pwr) and NMI / programmers switch (cmd-pwr) functionality is actually implemented by the Egret ADB (and other stuff) microcontroller, which is the same on both the CII and LC, not the main Eagle (CII) / V8 (LC) chips (which aren't quite the same, although they are obviously close cousins).

[@TheFurriestOne]

I mean, you could theoretically drill a hole in the board to make that pot adjustable from the back side... (provided no traces cross that area on either side and you de-solder the pot to get it out of the way during drilling) Great fixings!

[@strelatronics5533]

Love your vids! One thing about using the hot air station on an old board like this: Please use a preheater to distribute the heat evenly. PCBs get very fragile over time

[@Soup_it]

Great series! Thank you for all the hard work you put in.

[@mikespangler98]

Some Mac's needed a battery installed to boot, but if you power it up and let the capacitors charge a quick restart will give a proper restart. By the way, there is a program called Mactracker that lists the minimum and maximum OS for various Macs along with a good deal of other information. The Classic II does want System 7. Apparently it will run 7.6 though that might be a bit much. System 7.5.1 might work well though. The later versions bloated up quick. They really were meant for 68040 and PPC.

[@OffstagePfaffa]

Another possibility is something I experience with my G3, if you max out the RAM the Mac fails to bring up all the memory on the first boot attempt. After a couple of reboots it initializes all RAM and starts booting.

[@Evergreen64]

Dang Adrian! That was some great diagnosis.

[@the_kombinator]

I've used brake cleaner in pots before, works really well.

[@Neolith100]

Wow! Excellent soldering job! That's almost factory!

[@ShadeAssault]

Something I might suggest with the hot air station and surface mount stuff is putting a Kapton tape dam/covering over the nearby components, particularly connectors to make sure you don't melt/damage them. Found this trick through the channel Tronics Fix. He does this all the time.

[@rodgepodge2956]

Isn't it possible that the Classic II also needed the 12v? It was fixed between the first boot attempt (dead board) and the second attempt when it just freakin worked, right?

[@cowsgomoo4618]

I literally just picked up a Mac Classic today [2/25]. Never used any kind of Mac before. My first vintage pc too. All works but it won't format floppys.

[@Bergi2000]

I am deeply impressed and amazed of your repair skills! Congratulations ! ❤

[@kyorin6526]

Nice one Adrian, very satisfying.

[@krakenunbound]

If the computer doesn't work right with a cold start but does on subsequent restarts, my instinct is to look at capacitors as they seem to be losing a charge when powered off but able to maintain a charge on restarts. Just because a capacitor is not leaking doesn't mean it isn't any good. Replace every single capacitor in the whole system.

[@barrybpl]

Great job systematically tracking down that chip issue.

[@neakmenter]

what a lovely success! well done adrian! great sleuthing.

[@taskforce58]

Why would some address lines on the CPU have to go through a 22 ohms resistor but not the others?

[@ppokorny99]

Fast edge transitions can cause ringing on long traces. A small resistance slows down the transition and better matches the impedance between the trace and the chips and leads to better signals at transitions

[@marcokrijgsman8099]

Another piece of analytical craftsmanship. ... Yes, and then... plugging in the extra memory - and also pulling it out - while the Macintosh is running, that's hilarious. '... See if it allows that or crashes... the system freezes...' And switch the inboard memory switch from 2 to 4 MB while running... Hahaha I laughed. I found it genuinely funny to see. I have sometimes thought "what would happen if you do something like that", I also thought that the memory chips might be damaged as a result. But that is not the case. Apparently those chips can take a rough beating. Nice to know and to see.

[@br33ch]

Nice repair! As both machines failed on first boot and were ok afterwards, it could be related to the memory change requiring initialisation and a reboot to complete.

[@Rocket_Try]

Wonderful, I hope I can reach that level of expertise one day.😊

[@moofin4170]

13:00 check that the camera is not overheating (including sd card). Also check the manual, some cameras only record video for a certain amount of time.

[@piwex69]

The 74LS174 - you could also desolder it and check in the memory programmer (it has ttl diagnostic mode). But of course congratulations! You made it.

[@ScoopexUs]

Weird! And fortunate that the fault was in a 74xx chip, I guess the VLSIs can only come from identical donor Macs? I have a question: I don't see many videos on the original 1984 Mac, it's always SE or Classic. Why is that? I have one with some nice stuff and it's kinda neat to take it out and try some software now and then :)

[@ast3663]

..oh noo..its completly deaddd....oh we have a system memory error..verrry verry interesting..and wow, your tech knowledge is awesome

[@nickwallette6201]

I bought a genuine Molex de pinning tool for Mini Fit Jr plugs. It was also completely worthless. Used it three times and bent the tool. Tried to straighten it out and it broke. Apparently the only way to remove a pin from ATX connectors is with a Dremel and a hammer.

[@RetroBoxRoom]

The KPX-7 also seems to be able to use three mics. I'm assuming one is for the "DJ"? The leaflet seems he third mic as being a little different than the other two as well. I wonder if it had controls on the mic? I'm guessing being able to pause / mute mics? A great and interesting video as always!

[@perrylund3995]

Just a great bit of detective work.

[@Peter_S_]

XO was the development project title for the LC.

[@IsaacMcMillan-u7i]

I'm troubleshooting a classic II right now, and these videos provide a little more insight. A weird thing with the classic II, is that it doesn't boot unless I undervolt it to 4.84v on the 5v rail, and 11.78v on 12v. It displays a sad Mac if I boot it on exactly 5v. The sound still doesn't work even after recapping.

[@smakfu1375]

SE Mac is absolutely Best Mac. I have had mine since 89 (it was made in 87), and I’ve had a Radius 020 + 68881 accelerator (and 4MB of RAM) in the thing since 1990. Just checked that it was still a-okay by firing it up and playing Prince of Persia on it (for far longer than intended). Other than clipping out the battery a decade back, I’ve not messed with the internals since I installed the Radius accelerator. If you’re going to buy a lunchbox Mac, the MacSE is the way to go.

[@prestongivens3594]

What a wonderful journey of tracking the gremlins through the brush! 🤣

[@ultrametric9317]

Good job. All that for a Mac classic. Amazing :)

[@MarSAttK]

Great video! You should make a video about the Mac Portable!!

[@Frankk79]

What about the SE/30 is it as reliable as the SE?

[@cklinejr]

Great video series.

[@vinny9553]

Hey Adrian. I actually have a motherboard from a Mac classic that I’ve disassembled a couple of years ago due to it being in bad shape and your more than welcome to have it. I also have a ram card that I’ll give you also

[@starsundsternchen802]

I'm really eager to see a video about the GDR computer KC85. Please do not let us wait for long.

[@jordanscherr6699]

20:30 My very first thought was broken trace, or bad wires. I.E. Something was just barely connecting and would not-connect at the slightest touch.

[@tyler8459]

Glad you got this working! Great video!

[@twocvbloke]

In the previous cap vids and looking up on what to soak the juice with to dissolve & neutralise it, I found that the stinky liquid kind of caps used DMF, or Dimethylformamide, which apparently causes plastics to swell and fail (explains the leakage!), and when it decomposes, it produces that fishy odour that we all know and love (he laughs!), apparently quite a common solvent used in chemistry aswell... :)

[@stevemobi]

Thank you that was a really interesting video. I had a question though, because I was thrown off and actually thought you were on the wrong track with the address line. I understood everything you said about the address line being bad would cause the memory to behave in the way you describe (i.e., the same byte would appear in multiple places at that spot). Why I didn't think the address line could be responsible is because why would the system think it has only 512k of RAM in this scenario, as reported by Finder. I assume most systems use hardware and circuitry to detect how much memory is in a system, and the fact that you need to set a jumper, and the system immediately crashes when you plug in the board support that. So I assumed something was just making it seem like 4 of those RAM chips on the board weren't there or something.

[@jscipione]

18:52 You tested without 12V earlier, with 12V here. The classic 2 mb must also require 12V to boot.

[@DarthEd77]

I love the Mac repairs! Have you done any videos on the Mac II or IIci or IIfx?

[@ralphshoop8822]

He has done several IIci videos. I just typed IIci in the youtube search part of his video section.

[@cklinejr]

I need to dig out my SE and Classic out and check their cap situation.

[@timhorn3829]

I love Max. They were really good computers back when they were commonplace in schools

[@fledgeking]

Apple's new macs certainly aren't in the same category they used to be. It seems like Apple's aim with their Mac studio/mini lineups is professionals. I think Google and its partners are just offering much better deals to schools for chromebooks- not to mention stationary computers are such a small percentage of school computers anymore!

[@mfree80286]

23:00 What are the odds that the reset switch contacts were shorted and repeated manipulation finally cleared it?

[@alexclassicmac]

Great job, Adrian! It was very informative to see you narrowing down and fixing the issue 😊

[@TheTEKNOistSociety2024]

Man, you probably have a lot of Macs and PC's. ;)

[@patprop74]

Adrian, the Mac Classic whisper, That should be on a shirt lol

[@pipschannel1222]

Haha, nailed it on the 74LS174 ;-) Too bad you already shot that so my tip came in too late.. I like how you deduced the actual cause of the problem by using the debugger. That's a great tip as well and it will work on just about any broken machine with a debugger (if you're still able to run it of course) 👍 I just shotgunned this issue on the last Classic I repaired and just replaced that chip 'at a hunch' because I'm more of a neanderthaler-repairman LOL 😂 It did the trick for me though as these chips fail quite often! Also I wasn't able to run anything because with me it was a different output on that chip that went bad.. So I never got past the sad mac wether I plugged in the memory expansion board or not.. That Classic also had a bad VIA chip though which I did manage to pinpoint using my scope, so maybe I'm a neanderthaler with a diagnostic mindset 😁 You taught me quite a lot though and I really appreciate your in depth analysis of issues like these, Adrian. That's really empowering! 👌👌

[@thirstyCactus]

Amazing work!

[@redavatar]

I've had a similar result before when something first didn't work and then it did with every reboot after that. Leaving it turned off for a few weeks would make the problem return so I wonder if it's something that doesn't quite work until a certain chip has heated up a little. Unless you left a few hours between reboots, this might explain things.

[@ChaosHusky]

I smell dead ROMs.. Or some latent charges/static/dodgy connections that needs the system to warm up and cycle a few times! Quite common with Amigas too after being off a while, as well as having to re-seat socketed ICs like the Kick ROMs and expansions etc

[@Stoney3K]

The area under that 174 looked pretty corroded from cap juice so the chip may even be just good, but the traces and pads around it being conductive. That could also be what was causing the crosstalk on those pins.

[@fnjesusfreak]

I was figuring the Macs used that three-finger salute because of the Apple //e (it's the same key combo). I actually found that by accident...though it was on an LC II.

[@michaelhill2844]

Nice job Adrian.

[@SilentShadow-ss5xp]

You should upgrade one of these classic Macs beyond the limits with modern upgrades.

[@MrFixiit]

Nice job adrian

[@Raditude]

Apple+Ctrl+Reset still works on modern Macs. Hold Cmd+Ctrl and press the power button. It does an instant hard reboot.

[@fledgeking]

Camera Issue: If you are using a DSLR, especially one from ~10+ years ago, It could be overheating. Your only solution there would be to buy a newer camera. You can usually feel some heat even through that thick plastic. Also, make sure you don't have your auto-shutoff on (battery saver). Sometimes (With some Canon cameras specifically) HDR will cause some stuttering and such and may contribute to overheating. If you're getting a "lens/shutter" code on a canon, It could be a battery issue. I've seen multiple (canon) cameras with this issue, but both that I’ve seen were actual shutter failure issues. Make sure you check the connection (dedicated power) between the battery slot adapter and the power brick. Some of the barrel jacks are touchy. Battery pins: make sure all of the pins in your battery slot are properly spaced/placed, sometimes they get bent out of place and things get crazy. If You're streaming through mini HDMI: Mini hdmi is not my favorite port. Make sure the connection along there is good and that the capture card isn't actually the one dying. It can be hard to tell if you've got clean output on since your screen might be black depending on the camera. Also, if you're using the flip-around screen, the screen cable could just be struggling. Cables generally don't like getring mushed 😂. Moral of the story: I don't know if you're using a dedicated laptop or using the flip-around display, cameras like to fail spectacularly (If you have a macbook you might be screwed lol), and canon is a mess.