Macintosh Portable Sleep/ShutDown Issue

[hfrazier]

Hi Everyone!

Ok, so... I got this unit (M5126) a few weeks ago in a very clean but leaked-cap state. I recapped the entire logic board and it booted straight away and works in every way. Except...

After a few days of light use, it began to exhibit a strange PMU(?) issue. It can't go to sleep or stay off when I shut down. It will sleep and wake immediately, but has never frozen coming back from sleep. The only way to make it turn off is to remove the battery and power cord. I decided to play with it some more while writing this post and I can actually turn it off, but I have to be holding a key down... ?

These two short videos better illustrate what's happening and my discovery:

Original issues video: https://www.youtube.com/watch?v=hF6azqrtMx8

Insomnia battle, with keypress trick: https://www.youtube.com/watch?v=z1AaZCw5wso

Does anyone know what might be going on here?

Some things I have done/considered:

- I have not re-capped the LCD board.

- I tried disconnecting the HDD and booted from floppy System 6.0.8. HDD is not the issue.

- I tried disconnecting the floppy and booting OS 7.5 from the HDD. Not the issue.

- I removed the 4MB RAM expansion. Not the issue.

- It has a new lead acid 6V alarm battery in it.

- Should I isopropyl-wash the logic board? I already scrubbed it with warm soapy water and a toothbrush.

Thanks in advance everyone!!

 

[just.in.time]

If you have the KeyCaps desk accessory, open that and see if the computer thinks a key is being held down. May be a stuck key or a short in the keyboard developing.

That's one thing I don't like about my Portable. If you aren't sure if the computer is asleep, the only way to check is to power it on all the way by pressing a key on the keyboard.

 

[hfrazier]

Interesting. I just checked that, and it even exhibits this issue when the keyboard and trackball are disconnected. (Shut down with an ADB mouse.)

Playing with the KeyCaps application, the keyboard has no issues.

What if it's a pulldown resistor or a failed diode in the logic board that isn't pulling one of the chips' pins low or high and where a keyboard key-held brings that pin high or low so that it can properly go into sleep or shut down?

 

[hfrazier]

... So it seems to be working fine now...

:?:   :?:   :?:   :?:   :?:   :?:   :?:

 

[techknight]

Did you wash and clean the board really well? 

The portable has capacitor leakage right near both of those keyb/mouse connectors and it wreaks havok. Sometimes so bad youll lose an array of keys. 

 

[hfrazier]

Did you wash and clean the board really well? 

The portable has capacitor leakage right near both of those keyb/mouse connectors and it wreaks havok. Sometimes so bad youll lose an array of keys. 

It's definitely a possibility that I missed that area. I washed the board under hot tap water and scrubbed lightly with dish soap and an old toothbrush. Same method worked well for my Mac Classic II.. You're probably right, it needs another cleaning in that area.

 

[techknight]

If its not that, then you need to check the ADB pull-up state. if its being held low from either a broken trace to the pull up resistor network, or something else, it can do the same thing. 

I havent seen this "particular" symptom before, even though I have seen a ton of different stuff, so I can only take edumicated guesses here.