How to resurrect a Macintosh Portable?

[tjjq44]

Hi, I recently acquired my third (and of course non working) M5120 on ebay, the battery is dead as expected but apart from that the whole thing seems in excellent condition, even no (or at least very very little) caps leaking on the board! After some attempts to boot it without success, the first thing I did was to clean and recap the entire logic board, put a good battery but no way, it still doesn't boot   

It's acutally my third one: the first one died 4 or 5 years ago and was already hard to rely on when it accepted to boot, I keep it for parts (the crappy screen and keyboard you'll see on my video come from this one). I should also try to fix it but its mainboard seems in very poor condition, especially the hybrid board... On the other hand, the second I own is in great shape since I recapped it 2 years ago and has 4Mb of ram, a working original "conner" hard drive and... the rare backlight upgrade! 

Let's go back to the point, everything on this portable seems cosmetically fine, no visible broken traces or else, but it doesn't chime or even deathchime while my now dead "first one" still go till deathchime when I try to boot it   

I consider two possibilities: Something may have been shorted/broken by the previous owner and it may have destroyed some components... but when I power It up, power draw is about 400mA and I have stable 5v and 12v lines so It is most likely (I really hope) a rom or ram problem...

The bottom right corner is crappy but it doesn't prevent my working portable to boot with it!

http://www.youtube.com/watch?v=PKznUMqb5g8

In my video you can also hear little noise from the speaker...

+12v seems ok

+5v too

Nothing on -12v but on my working portable, when booted up, the external floppy port doesn't show any voltage here too...

Techknight, Uniserver, Bbraun, Bmow... or anyone else! if you hear me

 

[techknight]

I bet the SWIM IC is bad. Remove it, it may fire up. But only so far! 

But I will say this, that LCD is shot too!

 

[tjjq44]

Thanks for your answer, the swim isn't even warm, it's cold! I thought that when it was shot it would be quite hot? For the LCD I know but it works with my other portable and I'd like to keep the other parts of this mac is in their housing case for now, i'm just trying to make the logicboard come to life again

 

[tjjq44]

I can say the charge circuit seems to be ok: I let the battery and power adapter plugged last night and the battery which showed about 6.3V after my tests yesterday is now full at 6.55V this morning.

I've just measured power draw from the battery more carefully (nothing but the battery and speaker are attached to the logic board):

_ power off: 10 or 15mA

_ after pressing a key (power on): 250mA

_ after pressing reset button at least once: 400mA

_ after pressing both buttons (power off): 10 or 15mA again

 

[aplmak]

Take all of Techknight's advice... he's always got the correct diagnosis when it comes to a portable! He's brought hundreds back to life!

 

[tjjq44]

The main problem is I don't own any tool to unsolder such a chip, my soldering iron would make more damage than anything else

 

[techknight]

Ouch. If thats the case then this one may be beyond your capabilities. Youll need a hot air rework station, or at least a heatgun with the ability to control the intensity and direction of heat. 

The portable has a design flaw that when 1 of the 2 red wires in the 4-pin molex loses power for any reason, it goes completely out of regulation and can fry a multitude of ICs. First one being the SWIM. the SWIM is super sensitive. it can fail, and does fail. Sometimes they will get hot. Most of the time they stay cold! However it fails, it will fail in such a way that it holds up the bus, and it will NOT boot, Monitoring CPU bus states, gets stuck in a constant bus error condition. This is caused by the failed SWIM. 

 

[tjjq44]

Ok thank you! It's clear now, maybe it's time for me to invest in this kind of tool In case I can't make it work nevertheless, is it possible to send my board to you so that you can fix it?

 

[tjjq44]

Bad (and some good) news...

I received my hot air rework station 2 days ago, and I managed to remove the SWIM correctly! But when trying to boot, nothing changed, no chime and screen stays as pictured before

I also own a powerbook 100 which never wanted to read floppies (showed X instead of ? on boot up with or without a disk...) but booted fine from SCSI devices. I kept it for spare in my closet since I have another working one.

Today, I decided to remove its swim and put the one from my faulty mac portable instead and... tada!!! Now it's fully fonctionnal again (this is the good news), so it isn't the swim which hangs up my mac portable...

Techknight, any idea?

 

[techknight]

without really good and really clear shots of your logic board, I dont know. 

Usually from my experience the SWIM holds up the bus. But in your case it could be a corroded/broken trace, possibilities are endless. Could be a bad MOSFET switching 5V somewhere. 

One last thing to check, To the right of the CPu, and to the left of the video IC, there is a group of 74 series logic. like 74LS20, and some other stuff. When the machine is on, feel these. they shouldnt be warm at all. if they get warm, or getting almost too warm they are bad, I have seen this a couple times. 

Also, the 74HC244/74HC245 ICs directly above the CPU, and above these logic circuits buffer the bus, and I have seen these traces break/corrode and will cause this. 

Keep in mind, not all portable boards are salvageable! out of 40 or 50 I have done, I think there was 6 or so I couldnt fix. 

 

[tjjq44]

I'll make clear pictures of my motherboard this evening when my wife comes back from work!

I touched these ICs and they never get any warm... I have a more strange issue now, I think something goes wrong in the power management since I never get anymore sign of life when hitting the keyboard... The +12v is permanent on the floppy port as soon as the battery is connected and except from sometimes strange noises from the speaker nothing on the screen. On the 5v pin of the floppy port I measured about 0.3v... :'(

The battery is about 6.45V so everything should be fine... I managed to get the +5v running once but not really 5v, rather 6.1v...

Rather than try and error, the smart (and less time consuming) solution would be to get schematics or a troubleshooting procedure in order to master this very poorly designed machine!!

 

[techknight]

Rather than try and error, the smart (and less time consuming) solution would be to get schematics or a troubleshooting procedure in order to master this very poorly designed machine!!

Oh, that would be nice if either one of those were available for that board. But sadly, its not.

 

[tjjq44]

Her are some pictures of my logic board,

More detailed pics here:

http://tjjq.free.fr/mac/pmb-top1.jpg

http://tjjq.free.fr/mac/pmb-top2.jpg

http://tjjq.free.fr/mac/pmb-bot1.jpg

http://tjjq.free.fr/mac/pmb-bot2.jpg

They aren't as clear as I would but it's the best my digital camera can do

I'm really thinking about selling it now, repairing will be far too time consuming and maybe quite expensive as well... Even non working portables are selling pretty well these days

In addition, I still have my working one with backlight upgrade and now 2 working powerbook 100

 

[techknight]

You could sell it.... But the buyer knows that the board probably will not be an easy fix which may hurt its value, but it may not... 

Or. you can ship the board to me to troubleshoot and possibly fix it, but youll have to weigh your options as your in france.