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Mac Color Classic repair

inakito

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Hi,
i am trying to repair a Mac Color Classic. It was working some years ago. One day I tried to start it and the machine was dead. Not a single sound or signal coming out of the cpu. I have been told that for starters i should remove the logic board and power on the analog part alone, and that doing this at least the fan and hard disk should work, unless the analog part itself is dead. I have read somewhere that psu does not work unless the logic board send some signal (coming from the keyboard); is that true?

Well, if I remove the logic board and start the system nothing happens, it behaves like when the logic board is in place. Does that would mean the analog part is dead or might I try another test ?
Repairing the analog part looks like a daunting task!
 

VERAULT

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EVERY SINGLE one of these I have come across have Leaking SMD caps on the mainboard and Analog board. It needs a cleaning to remove all the corrosion and electrolytic residue as well as a complete recap. A dishwasher can be used for the cleaning but do your research on the do's and dont's before just jumping in blindly.

Its not daunting at all, its just tedious. Daunting would be having to repair broken traces if the leaking has gone on for years and damaged the boards.

Also keep in mind the unit WILL NOT BOOT UP without a keyboard plugged in(press the power button on the keyboard to turn on the color classic).
 

inakito

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So,do you mean replacing *all* capacitors in both the logic board and the analog? I see the logic board very clean. Where should I look to find the leaking and/or corrosion?
Another question I have: my logic board has no battery, can it power up without battery? Besides this, the chip that usually is connected to the battery has a jumper between pins 7 and 1. Is this intended to repace the battery or what? I can send detailed pictures if you want to see them.
 

bitfixer

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I had a similar problem with a color classic recently - it had been put away working a while ago and now failed to start. Replacing the electrolytics on the logic board along with cleaning the board with IPA did the trick, started right up after. It's not always obvious that the caps have leaked just by looking, it can look deceptively clean. But basically all of them will leak eventually.
It can power up without the battery just fine. But it does need an ADB keyboard to be plugged in to start. One that has a power button.
 

inakito

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Replaced all capacitors on logic board. Cleaned everything with compressed air and IPA. Two capacitors were visibly leaking. All replaced. No changes, the Mac still looks like dead. Time for the analog board? :-(
 

VERAULT

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Yes just as I mentioned earlier. The capacitors on the Analog board are as bad as the ones on the mainboard( again I have not seen any that are good.. I have seen machines still booting but the caps are leaky). They need replacement as well. Dont forget the caps under the RF cage.
 

GiGaBiTe

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Replaced all capacitors on logic board. Cleaned everything with compressed air and IPA. Two capacitors were visibly leaking. All replaced. No changes, the Mac still looks like dead. Time for the analog board? :-(

Replace every possible cap you can replace. 80s and 90s SMD electrolytics were shit and pretty much all of them are going to have leaked by now. I replace these things by the hundreds, not just Macs were affected with them, many PC expansion cards used tons of them.

But the same goes with normal radial electrolytics, the ones in the early crackerbox style Macs are notorious for failure because they're running smokin' hot with poor ventilation. I did a Macintosh SE for a customer earlier this year where all of the caps in the power supply had leaked, that was a mess to clean up.
 

VERAULT

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Replace every possible cap you can replace. 80s and 90s SMD electrolytics were shit and pretty much all of them are going to have leaked by now. I replace these things by the hundreds,

Yes! What he said....... My experience as well.
 

inakito

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Replaced everything on logic board and analog board as well with brand new quality capacitors. Result: NOTHING!. It behaves as before. Totally dead.:-(
I posted this question before with no answer, allow me to repeat it now: *IF I remove the logic board* and set the power button ON, should I notice any activity on hard disk, floppy disk drive, fan or anything else?
 

daver2

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I have been trying to hunt out the schematics for the Mac Color Classic without much luck at the moment. I have found the schematics for the boards - but not for the power supply unit.

I would have said YES from my experience.

As far as I can ascertain, the ON/OFF button really is an ON/OFF button and switches the incoming mains supply itself. Based upon this, when turned ON, the power supply should feed everything.

It is a switched mode power supply - so it shouldn't be operated without a load present. You should also remember that a switch mode power supply (primary side) is directly wired to the mains - so can kill...

Can you ascertain what voltage the fan actually is? Is it a mains fan or low voltage fan?

Are you able to measure the low voltages from the power supply with a multimeter?

If you need some help to do this - ask first before attempting anything...

I suppose the obvious thing first - you have checked the state of the battery haven't you?

Dave
 

VERAULT

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Replaced everything on logic board and analog board as well with brand new quality capacitors. Result: NOTHING!. It behaves as before. Totally dead.:-(
I posted this question before with no answer, allow me to repeat it now: *IF I remove the logic board* and set the power button ON, should I notice any activity on hard disk, floppy disk drive, fan or anything else?

yes, you should hear the psu/fan come on as if it sounds like a computer turning on. (without the board installed)
 

Timo W.

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I posted this question before with no answer, allow me to repeat it now: *IF I remove the logic board* and set the power button ON, should I notice any activity on hard disk, floppy disk drive, fan or anything else?
NO! Not only is the logic board required, but also an ADB keyboard. The power switch does *nothing* on the color classic, apart from letting mains voltage in. You need to press the power key on the ADB keyboard to turn the system on.
 

inakito

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So, do I need the logic board in place and the keyboard present and the soft-power button pressed, just to hear the FAN running ? In other words, would the fan move at all if the logic board is not present or the keyboard is not plugged in, or when I am not pressing the soft-power on keyboard?
 

Timo W.

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So, do I need the logic board in place and the keyboard present and the soft-power button pressed, just to hear the FAN running ?
Yes, exactly that. Absolutely nothing will happen until you hit the power key on the keyboard. No fan, nothing.
 

inakito

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So, might happen that the full system looks dead just because the soft-power button is not working?
 

Timo W.

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It's certainly a good idea to use a keyboard that is known to be fully working. :)

With the power switch on, you should be able to measure 5v on the ADB port.
 

VERAULT

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NO! Not only is the logic board required, but also an ADB keyboard. The power switch does *nothing* on the color classic, apart from letting mains voltage in. You need to press the power key on the ADB keyboard to turn the system on.

My Color classic Chassis will have a distinct high power charge sound on the CRT as well as degause sound.. and the fan spins when no board is inserted.
 

inakito

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Well, nothing happens when I connect pin 2 and 4. And there is no +5V on the 3-4 pins either!
And yes, I can hear the degauss sound when i power on the mac. Fan does not spin.
 
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inakito

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BTW, my logic board is the one with 4.5V battery (not 3.6V; it has a 3pin jumper to connect the battery and there is no battery socket). I dont know if this may be of some importance on this subject.
 
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