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#1 2015-10-31 01:08:52

MJ313
Member
Registered: 2014-09-23
Posts: 498

8550 powers itself back up after shutdown

Pretty much what the subject says. My 8550 has decided that it prefer to not be shutdown. When I attempt to shut it down, it immediately turns itself back on. Also, it powers itself up as soon as I plug in the power cord. I've checked the power switch... seems fine and not stuck down or anything. Reset PRAM, checked all Energy Saver settings, everything seems fine. Does this sound like a power supply issue? Anyone run into this?

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#2 2015-11-01 06:02:08

volvo242gt
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From: Duvall, WA
Registered: 2014-05-22
Posts: 406
Website

Re: 8550 powers itself back up after shutdown

How do the caps look (on the board and in the power supply)?  One of my previous machines used to not power down by itself.  Would start up just fine, but the only way it shut down was to unplug it.  I don't think it'd boot up as soon as it was plugged in, tho.

-J


68K: Q650 48/1.2G/CD
modern: Mac Pro 2.8GHz 8-core 6GB/500G/DVD-RW, A1150 MBP 2GHz CD, 2GB/80G/DVD-RW
Pre-Mac: ][+, //e
other: iPhone 6s 128GB Space Gray

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#3 2015-11-01 11:12:34

LCGuy
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From: Sydney, Australia
Registered: 2014-05-13
Posts: 810

Re: 8550 powers itself back up after shutdown

You're not using an S-Video cable as an ADB cable by any chance are you? My Beige G3 used to power itself back up after being shut down..eventually found out it was the S-Video I was using in place of an ADB cable that was somehow triggering pin that powers the Mac up.

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#4 2015-11-01 15:07:44

MJ313
Member
Registered: 2014-09-23
Posts: 498

Re: 8550 powers itself back up after shutdown

Thanks for responding guys. I am using a normal ADB cable that I pretty much use whenever I hook up my keyboard to any mac, so I think that's good. The logic board caps and power supply caps all *look* good, but yeah, I have no idea. I guess I will start with replacing the power supply caps, short of anyone saying don't bother, because it's x, y or z.

Here's the ps board... this thing was kind of a pain to take apart.

DSC04702_zpsryrz5ty4.jpg

Last edited by MJ313 (2015-11-01 17:57:58)

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#5 2015-11-07 17:04:57

MJ313
Member
Registered: 2014-09-23
Posts: 498

Re: 8550 powers itself back up after shutdown

Well, I am waiting for the PS caps to come in. Today I decided to poke around the logic board... didn't think there would be any issues with those caps, as it doesn't seem too many people are recapping Power Mac's right now. I figured I would wiggle one 47uf cap off to see if there was any sort of leakage underneath... and the little sucker slid right off its leads! It left them sticking right up! yikes

4 of the 47uf caps on top did the same. Just a slight grab and they pulled right off. I doubt that should happen. So now I'm gearing up to do the board as well.

Last edited by MJ313 (2015-11-07 18:37:55)

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#6 2015-11-07 17:24:54

bbraun
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Registered: 2014-05-29
Posts: 1,064
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Re: 8550 powers itself back up after shutdown

Yeah, pretty much all beige hardware is approaching the age of needing caps replaced too.  I replaced the caps on a g3 aio I got from uniserver recently because some of those were leaking too.

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#7 2015-11-17 01:47:39

MJ313
Member
Registered: 2014-09-23
Posts: 498

Re: 8550 powers itself back up after shutdown

And so... I replaced all of the power supply caps... and logic board caps... took awhile to get the order in and get it all sorted out. They looked fine after my job... made sure of that.

And yet the ghost start ups still happened!

But I think I've finally nailed it down. After shutting down the machine, I pulled the Apple Extended Keyboard plug out of the back of the machine and by gawd it stayed off. 5 minutes later I stuck the plug back into the machine and after a few seconds the machine turned itself back on again! crazy. I suppose the keyboard has malfunctioned. I tried the machine with a different keyboard and the machine stays off.

Much was learned during this fun ordeal smile

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#8 2015-11-17 03:12:35

bbraun
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Registered: 2014-05-29
Posts: 1,064
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Re: 8550 powers itself back up after shutdown

After you posted this, I got the Macintosh TV I posted about, and in the course of fixing that up, traced through the entire startup path with the cuda, which I think is the same on the 8500's (and about everything else that has a cuda from the 9600 to the color classic maybe).  I don't think I can tell you any more than you already figured out, but the power on pin from ADB goes directly to the cuda, which is what controls the soft power.  There is a pullup resistor on that ADB line between the cuda and adb connector, that causes the line to be 5V idle, and the keyboard grounds the line when the power key is pressed.
It could be that pullup is weak?  Or more likely as you've found out, the keyboard is having issues.  I haven't busted open an apple keyboard recently to know what all could go wrong there.

I've got a centris 650 with a similar problem of randomly powering on, but mine seems to happen without the keyboard connected, so is probably the power supply.

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#9 2015-11-17 04:50:23

volvo242gt
Member
From: Duvall, WA
Registered: 2014-05-22
Posts: 406
Website

Re: 8550 powers itself back up after shutdown

^Or a dodgy motherboard issue.

-J


68K: Q650 48/1.2G/CD
modern: Mac Pro 2.8GHz 8-core 6GB/500G/DVD-RW, A1150 MBP 2GHz CD, 2GB/80G/DVD-RW
Pre-Mac: ][+, //e
other: iPhone 6s 128GB Space Gray

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#10 2015-11-17 10:06:48

Schmoburger
Member
From: Australia
Registered: 2015-04-21
Posts: 281
Website

Re: 8550 powers itself back up after shutdown

bbraun wrote:

Yeah, pretty much all beige hardware is approaching the age of needing caps replaced too.  I replaced the caps on a g3 aio I got from uniserver recently because some of those were leaking too.

Yerp, whilst they are less common points of failure at thhis point, the beige Powermacs definitely are not immune to cap issues... I have both a PM7300 and a WGS 7350 both of which fail to boot up after the initial chime, and one of them was powering on the moment it got power, then turning itself off a little later... still having not booted.

but yes, having pulled both boards out for inspoection, there is definitely evidence of cap leakage in various spots on the boards, and i can rule out the power suplly as being problematic in the case of at least one of them, as the 7300's unit is now flawlwssly powering my Franken7600. and well, the 73/5/600-series boards are knoiwn to be among the most stable and rugged of beige powermac boards. For whatsits worth,i thiink wecan expect to be recapping our beige powermacs with ever-increasing frequency over the coming years, and eventually, even the new world stuff is going to be on the radar for cap-jobs.


Stay hungry... Stay foolish.
G5 2.0DC, Yikes G4/500 Sonnet-Enhanced, B+W G3/450, 9600/200MP, 7600/200, iMacs DVSE Graphite and 600 Snow, 7220/200, WGS 7350/180, 6360/160, 5500/250 DE, Pismo, 2x Lombards, 6100/66DOS, 2x CC's, 3x Pluses, 512K, SE/30, SE Superdrive, 2x Classics, IIvx, IIci, IIsi, 3x LC520, 4x LC575, 5x P580, LC, LCIII, //gs LE, 2x ROM 02 //gs', IIe... and I'm outta characters!

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#11 2015-11-17 13:50:02

MJ313
Member
Registered: 2014-09-23
Posts: 498

Re: 8550 powers itself back up after shutdown

Hey Rob, thanks for that info. If it starts acting up with the new keyboard, that's the first area I will take a look at. I am wondering if ADB hot-swapping fried the keyboard. I hardly ever do it, but I can remember doing it at least once with this machine/keyboard combo.

Last edited by MJ313 (2015-11-17 13:51:09)

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#12 2015-11-17 14:14:02

Schmoburger
Member
From: Australia
Registered: 2015-04-21
Posts: 281
Website

Re: 8550 powers itself back up after shutdown

I would be disinclined to think hotplugging would have caused the issue... it'd seem more likely it'd blow the fuse and make the ADB inoperative if anything.


Stay hungry... Stay foolish.
G5 2.0DC, Yikes G4/500 Sonnet-Enhanced, B+W G3/450, 9600/200MP, 7600/200, iMacs DVSE Graphite and 600 Snow, 7220/200, WGS 7350/180, 6360/160, 5500/250 DE, Pismo, 2x Lombards, 6100/66DOS, 2x CC's, 3x Pluses, 512K, SE/30, SE Superdrive, 2x Classics, IIvx, IIci, IIsi, 3x LC520, 4x LC575, 5x P580, LC, LCIII, //gs LE, 2x ROM 02 //gs', IIe... and I'm outta characters!

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#13 2015-11-18 02:24:47

bbraun
Member
Registered: 2014-05-29
Posts: 1,064
Website

Re: 8550 powers itself back up after shutdown

volvo242gt: Ah right.  In my case, that's a pre-cuda machine, so something on the board could be bad too.

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