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Macintosh Portable only works when connected to the AC adapter

Yup. Its the hybrid itself. When i get time (hahahahaha) i am going to make a new pcb to replace it.

Also feel the SWIM. if its getting excessively warm, its bad. Sometimes the 5.2v regulator runs away to 7.5v and it cooks it.

 
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I think I have the same exact problem on 2 portables. If anyone has found a solution I would be interested in learning what is wrong with it. Thanks!!!

 
Must recap KenB123... and clean that board WELL!!! I take my 5120 or 5126 boards.. when the old caps are removed and you've cleaned the pads... bring it to your bath tub.. grab a bottle of 91% rubbing alcohol and spray it on the board.. (put on rubber gloves) soak the entire board well.. and then I take a tooth brush and scrub in all the chips (ic's) legs... stuff hides under the chips.. after scrubbing with the brush I then do a shower again of 91% alcohol to remove anything the brush jolted loose.. then I do the other side just to give that side a clean.. Finally I shake the board to get excess alcohol off and put it in front of a blowing space heater at a distance to dry it off... (not too hot) or a hair dryer would work.. My boards come out real clean using this method. As Uni has said before that electrolytic goo get's all over the place in spots you cannot see.. sometimes the goo sealant from the hard drive drips down to the board too...right near the processor chip.. If after that and recapping is done you still have issues techknight is the portable king!

 
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yeah i find that a good recap + wash + plus a good dry off with a compressor.

is the best... the crusty electrolyte comes off the best with hot soapy water and a light scrub.

Techkinght has the schematics for this bad boy now.

and before that he spent a lot of time , with many hand written docs, where he toned out lines from I/C's

and documented it... helping em to figure out faults.   

 
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I'm back!

Today I decided to bring the beast back onto my workbench. So far I fixed the squeaking noise from the speaker by cleaning the board again and swapped the mechanics of the hard drive with another one with a good gasket (the models with a green label seem in better shape than the ones with the orange label). but the main problem still remains: It does not report the battery capacity correctly. It does know when a charger is connected (I'm using a bench PSU limited at 1.4A so I can also track the current going into the portable) and charges the battery fine. When both the battery and the charger are connected, it works perfectly, but when I remove the charger the level on the meter quickly drops down, but the machine keeps running if you do some lightweight stuff.

If I try and boot it from battery only it chimes but then it goes crazy once it tries to start the hard drive or access the floppy.

The battery is a brand new SLA brick and the portable has been completely recapped, I also reflowed the Hybrid with flux but it made no change.

At this point I'm also sure that there is a broken trace or via somewhere, but I cannot find it. The voltage on the power manager IC follows the level of the meter on system 6. When the charger is connected it hovers at around 3.6V, when i remove it it drops down to 2V and goes even lower when doing intensive tasks (when it lowers most of the time the system crashes or freezes)

 
the battery ADC is generated by an op-amp in the Hybrid (non backlit) or the main quad-op amp (backlit). 

it passes through an R-C Filter and then to the PMU. you should check these connections. 

Pin 52 of the PMU contains the battery signal. That signal goes through R151 and C107 which is the low pass filter network. 

That signal then goes all the way back to the Hybrid. There is another cap there to filter that signal as well. check everything. 

 
The voltages shown in my posts above are measured at pin 52. 

I can confirm that the signal comes from the hybrid (from the last pin, the one close to C15), goes thru a low pass RC filter and then ends at pin 52 of the PMU. I could not find a capacitor near the hybrid.

within the hybrid, the signal seems to be coming from pin 6 (output) of the OP20 closer to the edge, which seems to be configured as a voltage follower. only the non inverting input seems to be used, which is connected to pin 4 of the hybrid.

 
Maybe that opamp is not a follower afterall...

What is C15 supposed to do?

I also found out that the to 5V rails (tabs on Q16 and Q20) lower in voltage when both battery and PSU are connected.

 
Progress! 

I Fixed a bad connection on C15 and now the portable boot up every time from the hard drive even when powered only by the battery. I can also use and eject floppy drives, copy its contents to the hard drive and the portable never crashes.

The only problem that now remains is the battery meter, as soon as I disconnect the power adapter, the meter slowly starts dropping down and gives me a low battery warning.

right now it takes more time to drop, and sometimes it settles at about 20%. The battery is fully charged and it measures 6.3V.

 
Maybe my portable is not that sick after all.

I measured the battery voltage directly at the connector on the logic board and it was around 5.9V - 6V, Which the portable should correctly report as "low". (5.8V should be the cutoff voltage)

I connected my bench power supply directly to the battery terminals, and if I vary the voltage between 6V and 6.5V, the meter reports the battery level correctly.

I was connecting the SLA battery with some crocodile clips to the battery terminal in the bay, maybe it was causing too much of a voltage drop.

This also might explain the battery meter jumping all over the place when it was doing some power-intensive stuff or failing to boot with a hard drive connected to it

Lesson learned, Ohm's Law might create some trouble when testing portables!

In a few days i'll 3D print a new box to house the battery and adapt it size to the original one, and I'll make sure to use beefy wires.

EDIT:

At this point I might as well make a LiPo pack with a DC-DC converter and adequate protection (Fuse and diodes) and make a plug for the DC jack on the back.
This should make it lighter and improve the battery life of this beast

 
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Yesterday I turned it on and it decided to behave erraticaly again.

Just for fun I ran a copy of MacTest Portable and it reports a problem with the Power Manager. It suggests replacing the logic board and that's it.

Does anybody have a schematic of the power manager IC or at least a pinout?

 
Thanks for the schematic!

Yesterday I spent a few minutes with it, I ran MacTest Portable again without the modem card installed and it passed the logic board test.

The modem board hasn't been recapped, and I don't really need it.

But even when it passes all of the tests (with the power supply and battery connected), it still shows the same issue: very unstable when running off of battery power.

Also MacTest reports the battery voltage from the ADC and it seems correct when running with the power supply and battery (a bit more than 7V) but (like the battery meter) drops down quickly when powered by battery only.

Could somebody try to run MacTest on a fully functional Portable?

Thanks!

 
I just ran into a Portable board doing very similar issues. A Couple years back, i had a portable that had the exact battery issue. I remember a broken trace to the 3rd cap, at the right and the Op-amp and resistor pack change out. 

The LT1179 IC is getting noisy, and I noticed at a 6.2V input, the 5V regulator was a low 4.6V, and wouldnt go into proper regulation until the input voltage was near 7V. That aint no good. 

So I got some LT1179 ICs on order, hopefully it works. Those little buggers are pricey! 

Just above that IC is a highly proprietary resistor pack made for apple that forms the voltage dividers, and feedback networks for all those Op-Amps inside that IC. If one of those is bad, well.. your F****D, as I dont have this resistor pack mapped out. I need some fuming nitric acid and a vent hood to decap it and figure out its internal layout and resistor values. 

 
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Oh, Check continuity between C26 and Pins 14, and 15 on the Op-Amp LT1179. that breaks ALOT. and if it does, your battery meter and ability to stay on goes to hell. 

 
Thanks

Right now I don't have the portable with me, but I'll check the board as soon as I come back home.

Removing the LT1179 should be easier than it looks, if you heat the ceramic base with a heat gun you should be able to lift it off without desoldering the hybrid. Never tried on a portable, but it worked on another vintage board which had an 8 pin DIP IC on a ceramic hybrid.

techknight said:
 I need some fuming nitric acid and a vent hood to decap it and figure out its internal layout and resistor values. 
Click to expand...
If you go this route you may risk damaging the etched resistors, you can actually scrape the top layer with a knife and expose the traces (I did it on my board to check for continuity and voltage drops). Also, not all of the pins are used on the board (or so it seems), I think that some of them were used by Apple to check the performance of the hybrid before soldering it on the logic board.

 
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