Macintosh Portable 5120. my mistake..ugghh

[jdulac88]

So I picked up one of these beast in my computer recycling business for $3.  In all my years of recycling this was the first one I had seen.  The case looked good.  So without knowing anything about them I plugged my universal power supply into it not expecting much. To my amazement it booted up perfectly into the iOS.  THe mouse worked and keyboard worked flawlessly.  I shut it down and left it plugged in.  As I sat down to do some research and started smelling the infamous electronic burning smell.  Quickly unplugged but I think the damage has been done.  After doing some research I know (I should have done the research first) i picked up a battery so i could try to boot from the battery.  I am only getting faint lines on the screen.  So I took it apart and examined the board.  The board is in decent shape except the first mosfet looked toasted.  I have since pulled that mosfet and ordered another.  Testing the mosfet shows the drain open at all times so I believe this one is bad which I will replace.  Is there anything else I can examine knowing what I did with the power supply?  Is it possible it could just be the mosfet that I toasted?  

I did pick up another Portable locally for ALOT MORE.  Nothing on that one.  This new one's motherboard looks even better than the first except the ceramic on L8 is chipped in half comparing to my other board.  Not sure what this would cause?  

TIA for any direction.  

 

[techknight]

Oh boy... the damage is probably fairly extensive. 

All portables need recapped and washed by now at the bare minimum, AND a working battery. 

But now your beyond that point. Sadly without electronics troubleshooting knowledge it'll be very difficult to service it. 

 

[jdulac88]

I was hoping you were going to reply.  Saw some of your videos.  I got to say you are the man on these boards.

Any quick checks I can make on the other board.  Does nothing when I try to power it on?  Looks very clean and no obvious damage besides the L8.  Would the ceramic on L8 stop it from booting?  I'm trying using a 6v 5amp lead acid battery.  

I have some electronics troubleshooting knowledge but not enough without schematics to even attempt to repair.  Recap not a problem but reballing not for me.  I just can't believe I had a working board and fried it.  

When are you going to provide a service for a fee on these boards?

 

[techknight]

there are a ton of things that will stop it from turning on. However... the most common are: 

the PMGR IC, the Hybrid, any of the IRF9020s, there is a handful of logic ICs directly to the right of the 68K CPU, 74AC02, etc all go bad as well. And so does the SWIM IC. 

The SWIM IC wont stop it from powering on, but it will stop it from booting. youll get two fat dark bars in the display, no chime if any of those ICs are bad. 

if the PMGR and Hybrid are bad, you wont get any sign of life. 

I used to service these boards on a daily basis, but my full time job takes everything from me except a little time here and there, and unfortunately during those periods I suffer and recover from work "burnout". 

as a sole developer/electronics engineer of a startup company its tough and it takes just about all of my time. 

If I took on additional repairs like this, they would sit around for months before I got around to it. sometimes a year+ which for alot of people is unacceptable so I dont do it anymore.