Perfectly working Macintosh portable backlit M5126 just died

d3jsp

Active member
Really sad that my perfectly working Backlit Macintosh Portable M5126 just died. Really strange about the way it died too.
3 weeks ago I got a new battery from alaska360 and zulusci to replace the old harddrive. It was working just fine on battery (fully charged) and turned on and off without any issues. Thought I had some time before I need to have it recapped so I left it in the original suitcase for storage with the battery in it (probably a bad idea) and a brand new 9V.

Well, this week I took it out again to have it recapped and it wouldn't turn on; even with the 2 reset buttons on the side...nothing.
The only times it would turn on is when I try to open the battery bay or when plugging in occasionally and always gave a power management error. The screen and backlight worked fine of course.

Just had it recapped and it's still the same. The board is near perfect with no broken traces so the only thing I can think of now is the power management chip? Could it have died on itself in storage with a battery? I measured that pin 52 A/D filter on the PMGR chip is indeed receiving 5.1-5.3v depending if reset it pressed.

Anyone with diagnostic skills available to help take a look? Happy to pay. Would really hate to just blindly replace the PMGR :(
 
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Byrd

Well-known member
... just recapped, as in weeks? I'd be going back there and checking everything and surrounding cap goo that could have taken something out. Yes, the power manager/hybrid chip is highly prone to failure often being taken out by cap goo underneath.

- Try charging the main battery externally, new 9V, check the caps on the PSU.
 

d3jsp

Active member
Sorry, I meant it wouldn't turn on even before recapping, after sitting there with the battery for 3 weeks. Pretty sure the recap did nothing as it was already dead and I thought it could fix it
 

d3jsp

Active member
forgot to mention that there is no corrosion around the power chip at all, it's as clean as new
 

d3jsp

Active member
Doing more testing I found the pad under C116 was actually torn and I was able to repair the traces. Positive side of C116 is 5.4V and other side is ground. Here is the strange part: The portable won't turn on anymore from any keyboard or mouse presses but if I short the 5.4V side of C116 to ground with something like a multimeter it chimes and boots!!! I wonder if that means there are broken traces elsewhere.

There are also vertical lines across the entire screen that wasn't there before. The screen was definitely fine before with no cable damage.
 

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d3jsp

Active member
keyboard and mouse also works after the system boots so not sure why it wouldn't turn on with them
 

d3jsp

Active member
so it turns out keyboard is stuck typing the character "6", I'm pretty sure that's the cause! Not sure where the short is at though
Anyone know what could cause the video lines? broken trace to U15D from the 3 capacitors top right? They are really hard to test since all these traces go under chips
 

techknight

Well-known member
Broken traces. The portable is touchy, and attempting to run a portable or leaving a portable energized with its original caps installed and leaking is often more times than not, fatal.

Glad it runs but, the lines are trace related. you have an open trace between the LCD panel and the video IC.

If you have the original power adapter, do yourself a favor and pop that open too and recap it. Theyre pissing.

Every single OEM portable and powerbook charger are now leaking. I had to do a whole pile of them the other day.

the CR-76U Sony version of the Portable adapter is the worst offender. you have to strip the ENTIRE secondary side of the power supply and grind it all down, and re-tin it it is so bad.

I also RE'd the Hybrid controller inside the power adapter and made a copy to replace the original SHIN EI. They absorb moisture and the epoxy resin goes conductive.
 

Huxley

Well-known member
Broken traces. The portable is touchy, and attempting to run a portable or leaving a portable energized with its original caps installed and leaking is often more times than not, fatal.

Glad it runs but, the lines are trace related. you have an open trace between the LCD panel and the video IC.

If you have the original power adapter, do yourself a favor and pop that open too and recap it. Theyre pissing.

Every single OEM portable and powerbook charger are now leaking. I had to do a whole pile of them the other day.

the CR-76U Sony version of the Portable adapter is the worst offender. you have to strip the ENTIRE secondary side of the power supply and grind it all down, and re-tin it it is so bad.

I also RE'd the Hybrid controller inside the power adapter and made a copy to replace the original SHIN EI. They absorb moisture and the epoxy resin goes conductive.
Now you've got me curious - my backlit and recapped Portable is currently working fine, but AFAIK the power supply brick is still stock. Are you open to taking a commission on recapping mine?
 

d3jsp

Active member
Fixed the keyboard issue. Turns out Y0 was shorted to ground causing the number "6" to always be pressed down and machine not turning on at all. Interesting that shorting shorting C116 to ground is like plugging in an external keyboard from J22 and that bypasses the internal keyboard circuit allowing the machine to turn on. Woohoo

If anyone has schematics for the video chip U15D that would be amazing! Or know where the video lines under capacitor C11 goes to. Those pads on mine are completely corroded. Video circuit for the backlit seems to be completely different from the non backlit and it's gonna be a few nights of beeping party :(
 

SuperSVGA

Well-known member
The video circuit should be mostly the same. They just added in the brightness control potentiometer and disconnected the contrast (the trace is still there but it no longer connects).

Are you able to show which traces you are looking at? The traces under C11 are data/address lines along with reset.
 

d3jsp

Active member
Oh, that makes sense! It just seems like so far from measuring the pins on the bottom row of the lcd connector J19, they all go to different pins on the video chip for me 🥴

Hmm, maybe it's not those then! I'll have to get some pictures but I can't find damages elsewhere on the board.
Is it possible that I have partially damaged the video chip or video ram? I did try to plug in the screen to the board once when the power was on and that caused the whole system to crash. I would imagine that I wouldn't get any display in that case right?
 

SuperSVGA

Well-known member
It's hard to see on the picture, but it looks to me like you're not getting video D3 to the display. Check the path between that pin on the video connector to R171 on the back side, then to the video chip from R171.

d31.png
d32.png
 

d3jsp

Active member
Ahhh, that is the line that is under C14! It's connected but shorted to ground. I need to redo the soldering under that cap. Thank you so much!!
How did you create schematics for the entire board, this is so cool and I've never seen one for the M5126 before :)
 
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