Macintosh Portable M5120 strange behavior

[MrBlanchet]

Hello there,
M5120, already recapped some weeks ago.
When I turn it on it boots correctly via hard disk and after like 20 seconds appears the low battery alert and it goes to sleep mode. If I unplug the hd it goes to the floppy with question mark screen and after a minute it shuts down. What should I try? The 9v battery is new and as well the 6v 4.5 aH lead acid. Could be caused by some corrosion on the board or the hybrid is faulty?
Thanks.

 

[Big Ben]

Congrats on getting your Portable almost back to working!

Did you deeply cleaned your motherboard ? Sometimes capacitor goo goes under chips and may cause problems.

Also check the lead acid battery voltage shoud be above 6V by a good margin or it will be considered low battery and the portable will go to sleep/shutdown.

Makes sure the battery charges properly, beware, you can’t charge the battery when the computer is running, only compensate discharge IIRC.

 

[bibilit]

This is an issue with the Hybrid chip going bad or contaminated by capacitor goo.

At some point, the problem can be solved by cleaning the area and heating the pins with hot air after getting some flux in those same pins.

A new Hybrid chip has been designed

Recreating Macintosh Portable Hybrid Module

In keeping with my latest string of recreations, here's another one. I am working on recreating the 'hybrid module' from the non-backlit macintosh portable because these tend to die and do stupid things thanks to capacitor fluid damage or the coating cracking off of the high precision...

tinkerdifferent.com

 

[alexGS]

I agree with bibilit, faults in battery level sensing sound like hybrid module problems. I’ve fitted replacement hybrids and they have cured such things. I usually have to clip all the pins and remove each pin individually; it’s very difficult to remove a hybrid module intact