Diagnosing a Dead Mac Color Classic 

I think that you should definitely do more multimeter tests. There’s a high chance that there’s just a broken trace somewhere.

That's exactly why I wish manufactures would release their schematics and/or code for old machines like that (including ICs etc.) into Open-Source some time after they have been discontinued. It would make repairing so much easier and for machines as old as this (and even older ones) they wouldn't even lose money since they themselves can't get the parts needed anymore.

My process while repairing my Mac Classic was the same. Exhausted all normal logical troubleshooting steps, became manic and started chasing potential problems that didn't make much sense to chase, I did the exact same thing pulling new caps, chips off the board and soaking it in ultrasonic cleaner fluid in desperation, I even used one of those massage wobble boards to agitate it. Eventually I found if I bent the board in a very specific way I would get a slight sign of life, it was an invisible crack in a trace going to the RAM controller chip, right where the trace met the pad. Phew. What a pain.

To me at least, stuff like this is why FPGA, and software Emulation are so critical to preserving the legacy of retro hardware for future generations to know about, and enjoy, be it consoles, handhelds, computers, or other computing form factors like early cellphones, PDAs & Tablets.

RIP little Mac.

Also check those golden contacts at the front edge of the logic board; I've found many times the culprit is a bent pin (or dirty one) there because it's easy for people to missalign the board on unit re-assembly.

Back in 1993, I almost bought one of these. The main drawing card was the beautiful Sony Trinitron display. Ultimately, I purchased a Mac IIvi. The deal maker in that case was the CD ROM drive.

Always a great start to the weekend when there's a new Thisdoesnotcomp video! Thanks Colin!

id check the clock, then check activity on the bus lines. an oscilloscope would be helpful if you have one.

The good news is you still have at least one working machine. Better than none!

It looks like the kind of computer that an early 1990s school library would have as they gradually phased out card catalogs.

Funny how Friday changed for me from "the day when there is a good movie in TV" to "the day we go out" and finally to "the day when there is a new TDNC video on RU-vid". #lifegoals

I have the exact same issue with one of my color classics. I've sent it down to Amiga of Rochester for repairs hoping he can diagnose the issue since, like you, I was completely stumped. If he figures anything out I'll be sure to let you know!

I love these kinds of videos. Really interesting journeys with some great videography. Always stoked when I see these pop up in my sub box.

I enjoy watching your troubleshooting process. I had my fingers crossed that you'd be able to figure this one out.

DFAC is probably fine, it's only sound. Issue with a CC is doing anything with them on a bench. I am going to be taking a CC analog board and ripping the flyback off it to make a bench testing setup. I have seen this issue a few times and fixing it has been...less than successful. If the board wouldn't power on, generally can fix that 100% of the time. You really need to be able to work on these outside the system and have a scope.

Is the main crystal oscillator running? my next thing to check would be to see if the board has a working clock signal.

Good video. Not all can be solutions at the end of the video. I used to wish these were a but longer videos but maybe with what you are most passionate about you can elaborate. I try to watch every video and look forward to Fridays. Thanks for the escape.

Having a motherboard fall into your lap doesn't sound lucky to me at all! Some of those soda joints are really sharp, bro!

Always love a good happy ending, but appreciate sharing of trials and failures too!

Sometimes you win some sometimes you loose some. In this case while not all is lost yet, I imagine it wont be easy getting this fixed until parts become available.

Check the continuity of the edge connector that connects the board to the chassis. It takes a bit of a beating when the board is slid in and out of the chassis, so it could have been damaged some time in the past. One broken solder joint between the connector and the logic board is all it takes to cause problems.

Nice! We all have these machines that have to wait sometimes years. I have several projects like this. Best Wishes.

Check the edge connectors. Great video Colin!

Collab with Adrian's Digital Basement? He's into repairing Macs!

Es verdad querido amigo, vos tenéis que esperar un poco y la paciencia nos ilumina a todos. Buena suerte 🤞

I don't get the obsession with the CC. It's a cute enough computer, but people tear far better AIO Macs apart in order to marginally increase the CC's performance. The Mystic swap basically just leaves you with an LC575 with a lower-res monitor, mono sound, and no CD-ROM. I'd much rather have the unmolested LC575; it's more rare than the CC anyway.

love to see the hard partys of retro and th hard tyruths of sometimes its not a magic fix

Check for cracks and cold shunts around/under the ram slots.

Great video! I hope you’re able to get this CC working some day.

Isn't there another LC board that will fit? I think an LC550? It's not quite the LC575 but its something that can get the machine up and running

Have you tried a thermal camera? I have seen times where a bad chip will heat up and show on thermal. Could be worth a try if you have one or can borrow one.

Try heating some of the chips while powered.. heat will bring some back to life temporarily. Will give you an idea where the problem is.. also could use a thermal camera to find bad parts.. can also see visually where the board isn’t alive

Good luck, I had an LC-III and currently a MacBook 1432, so I fully understand.

tried replacing the small crystal!

I imagine that FPGAs are going to start becoming a convenient way to replace these custom chips with adapters.

I had a very similar issue a few weeks ago and discovered that 3 of the caps where shorted to ground. Did you continuity check the pads on the caps against each other? I.e. continuity check between both pads on each cap. Also had a bad ram stick in mine.

hope there is a part 2 :(

I love the Color Classic! Hope you can sort it out at some point…

This reminds me of an Adrian's Digital Basement video where he was working on a similar model. He routinely throws away the RF shields on all his restorations. Not a good plan with this one! 😀

Nice to see you getting down to the nitty gritty of board repair. It could be a microscopic trace crack you're missing.

Pressure wash the boards, use an air compressor to mostly dry it, then bake dry it in the sunlight for light for around 4 hours. After that, replace all capacitors. Also replace any other components that test bad, but seriously just go ahead and replace all capacitors first. Source: Me, the random dude that salvaged over a hundred flood salvaged computers after Hurricane Katrina. I had around 80% success rate for electronics flooded two weeks underwater, and my repairs tended to last 10+ years after.

Will a Performa 550 board fit in the Color Classic? Keep the 030 and double the clock speed?

is there no modern replacement or FPGA soluton. Can you test the port inside the color mac?

I could watch Colin diagnose a shoestring.

I just realized that your username literally describes that Color Classic at the moment.

Hi remember a guy at re-PC in Seattle thought I was crazy. I bought an LC 575 board for 50 bucks. It was brand new. I was having trouble with the sound but then I found out it was some other problem. I still have the brand new board hey hey so if they’re selling for hundreds I got a brand new one in the box for 50 bucks.

Hey, I really like your videos! Since the machine appears to be dead, I guess the hardware initialisation fails. I’d recommend to check the voltages on all chips. It’s difficult with this model, because it only can be tested inside the housing… I know that on older models the Sony sound ic checked the voltage levels and generated a reset signal to force all the other ICs into a reset state. The signal is withdrawn and the CPU obtains its reset vector. Standard memory is mapped to the ROM (I had a problem here with a PAL Chip on a Macintosh IIsi, which didn’t map the address right. It was getting warm which is a sign for a bad PAL). The MRH (Macintosh Reset Handler) is executed from there and RAM/ROM is remapped to their respective locations and then the P.O.S.T. sequence is initiated by MRH. The first P.O.S.T stage is testing rom and critical logic board circuitry before playing a chime. So addressing/memory could also be a problem. You could check the connections there or maybe test the onboard RAM. These are the kind of machines that keep you up at night 😂

Have you looked at seeing if a company can make a board for you like one of the sponsors of Action Retro's YT Channel PCBWAY?

Think you definitely need a scope and schematics, to check and trace if there's any actual data activity, like clock signals, and on data and address lines. Rather than just randomly changing components.

Could it be the onboard RAM chips? 68k chip itself, even?

Could be a good candidate for a Takky upgrade. You know you want to

What a finkity color classic indeed!

Stories like this really deter me from collecting old hardware -- I have no technical skills, any tools more sophisticated than a screwdriver, and no space to set-up a workshop. I have no capacity to undertake repairs, and so much vintage gear is either not working or it will eventually need an overhaul.

you can do it!!!! 💪💪

You ever thought to team up with ROSSMANN REPAIR GROUP? He has the fancy tools and does MACS.

What's going on with the pins on U8?

Did it do a Sad Mac chime? That's (almost) always a sign of a broken Mac computer.

I know only too well the frustration of testing, cleaning and replacing parts only to still have a dead machine 😪

Lease it out to a film prop company doing a early 1990s era production. I’m sure you can get a video adaptor to interface to the monitor. I recall having one of these color classics back in the day! Sold it used to upgrade to some Mac Performa

I better pull out my color classic and see if it still works. Haven't powered it in over a decade.

Maybe ask Adrian from Adrian's Basement channel, he fixes this in worst shapes and might have good clues

FWIW apple lc series sometimes don't like to start up without a working battery and then even with a battery ini it, still need an initial pram reset for a clean start, please have a try

hey, did you know certain models of macintosh computers won't boot without a cmos battery installed?

What about the RAM? I recall that a bad module kept your SE/30 from working.

Macs are pretty cool.

What, don't you have an ultrasonic sink? We need one in every home!

I have a Mac Classic and a PowerBook 145B. As far as I know, they both should work if I boot them up, but it has been several years since I have done that. They just sit on shelves in my home office as decoration. I'm getting worried about the CPU batteries bursting so I'm thinking I may need to open them up to check.

Does this Mac have on-board soldered RAM?

You kinda need to go full nuclear, strip the monitor and all its circuitry out of the case, plug the board in and start probing with an oscilloscope. Check you have a clock coming from the crystal and reaching everything, check the CPU reset line, check the CPUs main data line for activity, check the RAM bus for activity. You don't even really need to understand what is happening, grab a schematic and use it as a guide, all the different lines will be marked with a high/low on/off indicator so all you gotta do is make sure there is either activity or the line is high/low as stated in the schematics. If it should be high and its low, should low low but its high or should have activity (data lines mostly) but doesn't then that's your problem. If I had to guess though, its likely either CPU or RAM since you're getting nothing at all. Lastly, don't always assume its actually the thing you first think, for example if something is stuck high on the RAM bus it could be a dead ram module but its just as likely to be some LS74 logic chip on the same rail, again schematics will show you the full circuit so you can follow it back and find where it goes bad.

It would be cool in situations like this to see how feasably a M1 mac mini board could be slipped in quietly and adapted to the display (if such adaptor boards are even possible)

I know that it has been a year since posting this video but have you had any further luck getting it to work? The Color Classic is my dream retro Mac. I would love to get one

Chances are the power delivery diodes on the mainboard have shorted

Send it to Adrian Digital Basement, he is a wizard…

disappointing, but you tried your best! I'm sure you'll figure out eventually! Thank you for making this video!

Link to the intro music in description is still dead

I also have Macintosh Color Classic. It was working when I last put it into storage about two years ago... better take it out and make sure it's still okay... hmm....

Umh, I have a 040 board spare. I tested it in a Powermac 6000 series tower unit or whatever it was, and it worked fine. A 100 bucks and it's yours, my friend. :D

It's because you said "straightforward", that jinxed it. I once did they same and thus cursed a project compile. Now I'm forbidden to use that word in the office.

It wouldn't surprise me if this board somehow - by a cosmic coincidence - ended up on a Mac84 livestream. At least it's a relatively rare and valuable machine, so it's worth pouring time and resources into it.

You should try with the RAM chips (I not good with old macs but I had a similar problem with several old IBM with on-board RAM). It quite common that faulty RAM chips prevent booting. An other cause would be the CPU itself but it's a very rare cause.I repair computer for more than 20 years including retro ones, and on thousand computers I've repaired, faulty CPU only occured to me twice ! PSU can also be faulty but in your case, since you tested it with your working board and it was OK, the PSU is good.

Missing PRAM battery causes LC grade computers not to boot or display video and the Color Classic is identical to the LC.

i know i'm late how about the brightness?

Mmm. What about the gazillion connectors at the back of the board?

Was that a Futa chip?

I had this and had to reflow the ram chips to get it to come back to life.

To really trouble-shoot this you need to break out an oscilloscope and make your way through the startup circuits. One thing I would check is the built-in RAM.

Do you have RAM installed? I had your problem with a laptop in 2000'ish and it was because I installed the wrong CPU upgrade and it fried something on the motherboard. I put the old cpu back in and it would show power, but nothing on the screen. I think you have a bad CPU and or the CPU isn't able to function.

You need a scope and check all the clock signals first.

This is why I don’t like how Apple makes it hard to repair their computers with planned obsolescence! I love these Macs, but these computers don’t age well over time, these custom motherboards are just flawed!

You should write PCP on your gallon jug next time

Ah, engaging in a casual computer necromancy, are we?

It’s time you got an oscilloscope with built in logic analyser.

i had a color classic with no scsi swap the IC but no better and gave up (replaced with a lc757 :)

It looks like theres no ram installed in the slots maybe thats the issue?

Aren't two vias under U7 destroyed by corrosion?

It's obvious that its main processor chip has experienced an electromigration.

I wonder if the traces in the pcb are cracked somewhere and it's not a component

👍

ive noticed u have not tried different ram modules