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Macintosh Portable only works when connected to the AC adapter

Ferrix97

Well-known member
Hello!

I recently acquired a Macintosh Portable M5120, when I power it from a brand new (and charged) lead battery, it runs fine until it tries reading from the floppy drive or it spins up the hard disk, at this point the machine goes crazy: sometimes it will freeze, sometimes it will go in a reboot loop or in a sad mac loop and other times it simply turns off.

If I plug it to my bench power supply (set at 7.5V 2A) the machine will boot from the hard drive or from the floppy drive without any problems. when running and charging the battery it draws about 1.6A, it I remove the battery, the current drops to less than 1A.

When the machine completed the boot process (and the battery is connected), I can disconnect the power supply, but after 15 seconds it will report a low battery and then shut down. If I plug the power supply back, the battery level quickly rises until it reports that the battery is fully charged (and the charging icon disappears).

The board has been fully recapped and washed. I also added a 1Meg resistor between pins 16 and 18 of the Hybrid IC.

should I replace the mosfets?, the IRF9Z30 is quite hard to find nowadays.

If I cannot fix the issue, I might end up using a modified version of the Portable PowerBook Power Supply, detailed here, with added protection and current limiting.

EDIT: The current prototype of the the Portable PowerBook Power Supply power the portable perfectly!, I can fit the batteries and the electronics in the battery bay and then route a wire from the modem port that plugs into the power connector on the back. Tomorrow I'll try hooking it directly to the battery contacts or to the power connector on the logic board. I can 3D print a cap to prevent plugging an AC Adapter when the Portable Power Supply is installed

 
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Macdrone

Well-known member
It needs to run off the battery.  Re cell the battery and use the 1.5 amp charger or you will cause nothing but problems.  Do a search and you'll see pages and pages of issues.  Technight and Uniserver will expand on that more.

 

uniserver

Well-known member
The only person that can help you with this is one man.  techknight.

couple things though.

The Charging circuit is designed for 1500ma max.

and the on board battery needs to be installed.

do not run the portable with out a lead acid battery installed,

as i believe it does more then just provide the system power as some filtering.

usually when a portable does that, ( works when charger is attached ) but will not stay on after unplugged.

if you monitor the +5 rail you will notice that it does not remain stable as soon as the Charger is disconnected

and that is because there are rotted traces and the Voltage ref is probably no longer connected to the 5 volt regulator.

or the 5v regulator is bad or is rotted up... 

Flat out what you are dealing with here is CAP GOO ROT..

these scenarios are a product of Via rot, Trace rot, Pad rot.

so its going to be up to you to meter out the lines and figure out the problem.

i'v wanted to put together a document that includes specifics,  ( when 5120/5126 does this.. )  

(try this) kind of thing, but i have no time for that any more. 

there are pattern failures with these things,  but right now only techkinght has all this valuable information in his head

that is why, I and pretty much everyone else in the world have been simply sending these boards to Mike, 

because he is just the portable master.   he's probably been through at least couple hundred boards by now

and has all kinds of proprietary hand drawn schematics and diagrams .  and he is worth the $50 an hour he asks for.

 
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Macdrone

Well-known member
Im glad it recapped and hopefully technight and Uniserver can tell you the specifics of the other items your asking about, or do a search as they have covered the portables a lot about these issues.

 

techknight

Well-known member
There are 2 positive wires that go into the 4 pin molex plug. If the microswitch goes bad, only 1 of those 2 wires will see voltage, and it will do exactly this. 

But yes, you need a good battery. if you run it without a good battery, and use a higher current charger, that portable board will end up on my autopsy table. 

Also there is a problem with the non-backlit models. the cap goo gets into the ceramic substrate of the Hybrid IC and it will cause all sorts of problems. Also, that flickering and shutoff means the 5V supply is starved for current. 

The regulation for the 5.2V B supply is, you guessed it... the Hybrid itself. You need to test the continuity of the 9Z30 back to the Hybrid, and make sure its connected .If it is, you have trace rot, or a bad Hybrid. Assuming your running this from a GOOD battery. 

Also the undervoltage lockout is around 5.8V or so on the battery. so 6V isnt quite enough. you need 6.2V or better on the B supply. 

 

uniserver

Well-known member
yup a fully charged typical $11 dollar 5ah 6v agm is 6.5v 6.6v @ around 5.8v they would be considered dead by properly working portable.

the Actual OEM replacement solution,  is 6.8vdc fully charged,   

this times 3.

0800-0004.jpg


i just don't find them cost effective for the slight gain.  

 

uniserver

Well-known member
i would say this is about accurate discharge table,  even though its for the 4.5ah battery and not the 5ah ones i get.

Screen Shot 2015-09-09 at 9.04.11 PM.png

 

Ferrix97

Well-known member
The battery is brand new and charged, it is one of those normal black bricks. I just bought it for testing, since the Cyclon are crazy expensive.

I did a visual inspection of the board, but I didn't find any broken trace or via (with a light under the board).

The battery bay switch is also good. I made another cable from a dead ATX power supply and connected both of the wires to the battery and it still shows the same issues.

Which connections should I check?

Also, what is the purpose of the tantalum capacitor on the Hybrid module? when I was repairing another board I replaced it, and that brought the machine back to life.

 

techknight

Well-known member
that large tant is the -5V filter capacitor, and it doesnt have anything to do with anything except communications, etc... 

But the act of heating up the Hybrid to change it, alters the capacitance of the substrate because of the cap goo that gets onto it. THAT usually fixes it. albeit temporarily. 

 
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uniserver

Well-known member
i would not put voltage to both terminals as that would never be done in a normal situation, as to why you think that would be ok kind of bothers me.

seems like you know just enough to be dangerous. 

in a normal situation , to that 4 pin connector, it would be Either or.  there would be 9 volts to the one pin... OR there would be lead acid battery voltage to the other... never voltage to both at the same time. as the 9 volt battery is only there to keep what is in ram for only long enough to change the main lead acid battery.

 

unity

Well-known member
Batteries Plus has Cyclone batteries that match the originals for pretty cheap. Getting the original battery pack open is the real issue.

 

Ferrix97

Well-known member
Unfortunately I live in Italy, and a single Cyclon costs about 15€!, opening the battery should be easy.

Tried slightly heating up the hybrid, still no change. I also took a look a the analog input of the Power Manager chip, and the battery level displayed by the computer is related to the voltage present on that pin (from +2V to almost +4V). If there is a problem, it has to be in hybrid or in the components attached to it.

Also, what is the purpose of Q11? mine looks slightly darker than the others.

And just to make my life a little bit happier, the hard drive died... (Yes, I did clean the melted rubber before even trying to turn it on, in fact that drive worked for about three days)

 

aplmak

Well-known member
For the battery.. I use a hax saw around the sides of the top cover that is glued on... It so far is the cleanest way to get in the battery pack. Once inside I remove the Cyclon batteries.. I remove the gold tabs and try to keep as much of the metal as possible by pulling the gold pieces away from the solder joint.  I then solder two leads a black and red wire to the gold connectors.. First I scrape up the gold so I can get a good solder contact.. I then take the two gold pieces and glue gun them to the top cover where they are supposed to go.. I crimp battery connectors on the end of the wires and insert a small 6V alarm type system battery pack and connect the leads.. (one with the correct voltage and amps..) it fits in perfectly.. and use some foam tape to pad the battery in so it doesnt slide around. Then I replace the cover and use either clear tape or white tape and tape around the cover to hold it on.. It works perfect.. and easy to get back inside to replace the battery in the future..

 

Ferrix97

Well-known member
Hello. I'll try swapping the main MOSFETs with brand new parts. Unfortunately I cannot find the original IRF9Z30, but I found two suitable replacements: IRF9Z34 and IRF9540. which one do you think is the best replacement?

As for the battery, I'll worry about the mounting method one I get the machine up and running without issues

 

techknight

Well-known member
i would not put voltage to both terminals as that would never be done in a normal situation, as to why you think that would be ok kind of bothers me.

seems like you know just enough to be dangerous. 

in a normal situation , to that 4 pin connector, it would be Either or.  there would be 9 volts to the one pin... OR there would be lead acid battery voltage to the other... never voltage to both at the same time. as the 9 volt battery is only there to keep what is in ram for only long enough to change the main lead acid battery.
Incorrect. Both connections are tied together at one point, they BOTH see EITHER 9V (when the microswitch lets loose), or main B voltages. the 9V battery is switched in and out of the circuit through the microswitch. Its switched in when the battery cover is removed. 

I should know, I reverse engineered these things and fixed a bajillion of them. 

However, what I cannot remember is if 1 pin goes from 6V to 9V, while the other goes to 0V when the microswitch hits. But when the main battery is in, and the cover is in place, both pins are 6V. 

 
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Ferrix97

Well-known member
I made the measurements again and (as always) techknight is correct about the battery connector, There should also be a diode in series with the 9V battery.

About five days ago, the Portable started squeaking and the display flashing while the floppy drive was connected and/or in use (with battery and power supply connected).

Today I replaced all of the IRF9Z30 with brand new IRF9Z34 MOSFETs, but the situation is still the same. at this point I am pretty sure there is something wrong on the Hybrid or on the traces that go to/from it

 
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