Apple

Bought a Mac Color Classic which was described as having a "power on" problem.

Plugging the power cable into the unit, it make a short whine and then nothing happens.

I added an ADB keyboard and used the soft on button to turn it on. That didn't do anything.

Then I removed the motherboard and powered up the unit again. After 4-5 seconds of nothing, the PSU starts up and the fan beings to spin

While it's running, I plug in the motherboard. The systems continues to function, but no display. I see the green front panel light still on (left) but nothing else.

I plug in the ADB keyboard and try a soft start again. Nothing.

I remove the power cable, wait, unplug the motherboard, turn the unit on and after a few secs the fan comes on.

Not sure what is going on here. Any thoughts?

I could be wrong about this, but I don't think soft power-on works with the compact macs (at least it doesn't work with the SE/30). When the power switch is set to off, they really are off. But based on your message that it makes a whining sound when you plug in the lead, this appears not to apply to the color classic? Either way, I don't think I would plug parts in with power applied, because they were not designed to support that. I remember using a powerbook 180c where even pulling out the battery while the machine was on could fry something.
Some of these machines have a small button near the battery that is used to reset the microcontroller. It could also point to a battery problem, try removing the lithium battery for a minute and then replacing it.

The CoCla is a soft power on system, assuming that the rear switch is on. I would look at the PRAM battery. If the PRAM battery is dead, it will not generate video. There is no CUDA switch on the CoCla.

I concur with robespierre: don't mess with the motherboard like that. You will eventually kill it, if you haven't already.

Thanks. Definitely won't do that with the mobo again.

So the next thing to try would be a pram battery replacement.

It may need a recap - the surface mount capacitors tend to vent their electrolyte all over the board. Look for evidence of vented caps (dark oily areas) on the motherboard. Sometimes just cleaning that up with some alcohol is enough to get it working again short term.

http://wiki.68kmla.org/Capacitor_Replac ... or_Classic

The caps seemed ok - no oily residue or anything.

I have removed the 1/2AA 3.6V battery but do not have another with the same voltage. Will order a replacement and try again. Did a general blower clean to get (considerable) dust out of it. Of course, that made no difference either

Here are some detailed pictures of the motherboard with the battery removed. The battery had not leaked, btw.

I note, FWIW, that when my CC board's caps failed, there was no visible issue.

But the PRAM battery will be easier to fix and I'd do that first. The CC boards last longer if you leave the rear switch on and use soft-power to start it and shut it down.

1/2 AA batteries ordered. In on Monday. Hopefully that will do it.

This thing didn't have an HDD. If it works - fingers crossed - that would be the next mission... along with system software, which I don't have.

Just to add some extra flavor, I had a PPC clone mac that wouldn't soft-start if the power key was hit quickly, it spun the fans for a bit and then stopped. You had to hold the key in for almost a second, and it was like this when new. The kind of thing that could be very frustrating to diagnose if you didn't think to try holding the key in.
There is also a technique to force a mac to boot without a PRAM battery: turn it on and then use the reset switch. If there is no reset switch you can sometimes mimic the effect by quickly flipping the power off and on. Looks like there's an unpopulated S1 on that board, hmm.

robespierre wrote: Just to add some extra flavor, I had a PPC clone mac that wouldn't soft-start if the power key was hit quickly, it spun the fans for a bit and then stopped. You had to hold the key in for almost a second, and it was like this when new. The kind of thing that could be very frustrating to diagnose if you didn't think to try holding the key in.
There is also a technique to force a mac to boot without a PRAM battery: turn it on and then use the reset switch. If there is no reset switch you can sometimes mimic the effect by quickly flipping the power off and on. Looks like there's an unpopulated S1 on that board, hmm.

An unpopulated S1? That sounds dangerous. Could you please explain?

In the image "WP_20140918_19_32_19_Pro.jpg", you can see an empty square labeled "S1". This is where the PRAM reset switch would go if they had populated it.

Oh! Got it. Thank you for explaining. I take it this is not an issue, and merely a "defeaturing", at the factory, of an optional feature.

The CoCla never had such a switch on any production run.

A quick update. The quick on/off to emulate reset didn't work. Did that in conjunction with the soft ON on the ADB keyboard. Left the system on overnight and then tried to turn it on; no cigar.

The 1/2 AA battery hasn't arrived yet, so that's the only thing left to try, short of recapping. It really doesn't appear that the caps are in bad shape, but maybe there is a failure mode not involving visible residue or blown tops?

Any other thoughts would be appreciated. One thing I should mention is that the ADB keyboard I am using came with my Apple II GS. ADB is ADB is ADB, I believe, but just thought I'd be explicit about stating this in case there is some keyboard soft power on weirdness at work.

The IIgs keyboard works fine with Macs. As I mentioned above, my CC motherboard with bad caps had no visible failed ones either. It's to the point where just about every 68030-based Mac's capacitors have blown by now -- my IIsi, IIci and SE/30 all needed recaps (the CC was replaced with a Mystic LC575 motherboard instead).

Thanks! I used the link neko provided to order replacement tantalum caps. I don't trust myself enough to do SMT part replacements, so I will have to find someone to actually do the repair.

In the meanwhile, that PRAM battery arrival on Monday represents the last ray of pre-re-capping hope.

Gosh darn it. Battery didn't do anything. Recap here I come.

Any recommendations on recap service in the central Texas area? Guesstimate of a fair price to pay?

sgifanatic wrote: Gosh darn it. Battery didn't do anything. Recap here I come.

Any recommendations on recap service in the central Texas area? Guesstimate of a fair price to pay?

I had good experiences with Charles at MacCaps: http://www.maccaps.com/MacCaps/Repair_Service.html

Prices range from $25-55. It's pretty reasonable, and he does a great job.

Brilliant. Thank you, neko!