Portable logic board. Such extreme failure

[techknight]

Well as you may or may not be aware, I picked up a portable the other day specifically for hacking/modding. At first I thought i was going to convert it into a modern machine, but then decided not to. But it still not out of the realm of possibilities. 

But.. First I used the LCD to perform my backlight mod, but the LCD itself was bad with tunnel vision effects. So i switched to my spare. 

Then, I decided to pull out the logic board and recap it. 

But before I recapped it, I decided to check out the overall health. I think this may have been a victim of using the wrong power adapter or something. 

It had more fried chips than I have seen so far. What threw me off was the SWIM looked brown. instead of black. It also had a small crack in it, So i knew it was dead. 

Removed the swim, but it was still pulling a ton of current from the power supply. Several other chips were getting hot and smoking. I have outlined the chips here: 



Regardless, I was able to replace all the bad chips and the motherboard came alive. It works again. 

But, wholy cow! No idea what caused this sort of cascade failure. 

I figured I would share this with you all. 

 

[techknight]

On a side note: my original apple portable startup disk went bad. So that opted me to try something crazy. I decided to pop the diskette apart, and replace the actual disk material inside of it. Then snapped it back together and put the slide guard back into place. 

worked like a charm. I only did this because it was an original macintosh diskette. 

 

[unity]

Wow, thats bad. I will still say this is one of the worth designed boards though.

I have done the same with some other disks to preserve the vintage original look. I generally dont use them though, I use copies.

 

[techknight]

Yea, they arnt designed very well. But you gotta think it was in its infancy with a handfull of engineers that really didn't know. there was nothing to compare it to. There was no google to look up reference designs, which I quite often do. You had to go to the library and look at various circuit "cookbooks". I still have a couple of those. lol. 

But Sony was the electronics mastermind back in those days, and when they finally stepped up to plate, they got things right with the PB100. 

 

[unity]

Ya. There is NO comparison between the 100 and the Portable. Who was responsible for the design on the 100, was that Sony too? I was under the impression that Sony pretty much did it all. Im surprised Apple brought in Sony at all. Apple, even around the PB100 days, had a strong "not invented here" attitude.

 

[techknight]

Yea, I dunno. But the PB100 is based off of the portable, logically. But it has a completely redesigned power delivery system. 

 

[Elfen]

Those 74XX/74XXX seem to be 74AC, which if I remember are high speed CMOS. These were susceptible to blowing out when the amperage got too high. And from the looks of it, most seem to be part of the floppy drive circuit or the area there off. A bad or "killer" external drive was attached to it? It one those IIGS 3.5 uni-drives put in?'

At least you got it back running again. That's great!

 

[techknight]

Half those chips dont have anything to do with the FDD, the other half do. They would have to drive a shorted or very low impedance load, or get a voltage spike higher than +5V to die like that. 

 

[TheWhiteFalcon]

Apple handed the Portable to Sony and said "FIX PLEASE". The PB 100 was the result, which is why it's different from the 140 and 170.

 

[uniserver]

I think the portable is a fine machine.   

Cap goo / and L/A and 9v battery leaks can cause anything to go to heck.

did we determine the leaky goo from the HD might also cause rot on the mb as well?

I wonder if elfen is onto something with the UNIDISK and the portable.... ?  and dead SWIM's?

i think when you run a portable with the PowerBook adaptors 2.0 and even 3.0a adaptors ,  

that mixed with leaked conductive cap goo,  maybe mixed with other leakages from batteries and additional rot 

maybe created by the goo dripping out of the conner hd.

and with out a 6v lead acid battery in there to stabilize the thing....

you are going to cause damage and not even realize how much.

i have 3 dead powerbook 100 boards..  well 4 including the one that mike sent me.

SMT electrolytic caps all over the darn thing.

also with most of the pb 100's i have seen under the MB is a crap load of hand soldered re-work, diodes, resistors ... kinda hidden from view.

i don't think apple handed the mac portable to sony and said here fix this.

I think they handed it to sony and said can you please miniaturize this.

i guess think of the Powerbook 100, as a SONY VAIO 1.0  

 

[Juliet Elysa]

Wikipedia, the most reliable source on the internet, confirms that the 100 is basically a mini portable. A quote from the PowerBook 100 series page:

The PowerBook 140 and 170 were the original PowerBook designs, while the PowerBook 100 was the result of Apple having sent the schematics of the Mac Portable to Sony, who miniaturized the components.

Some other sources also say the same thing.

(Edit to try and remove the link to the Sony Wikipedia page. I failed, so if you want to go to their page click the S. :lol: )

 

[techknight]

Well I do know the power supply circuits have been redesigned, that was apparent when I saw the motherboard.

Yup I remember the wiki article. I thought I remembered seeing that somewhere.