Macintosh Portable backlit M5126 keeps blowing 7A fuses

[d3jsp]

Fully recapped and working but this is the second time plugging in a known working portable power adapter (works just fine on other machines) blew the F1 battery fuse. The machine would instantly turn off but can be restarted using power from the power adapter. Just will not turn on with battery. It even charges and shows battery charge correctly.

This doesn't happen all the time of course but just occasionally when plugging in the power adapter to charge when the machine is on. What could be at fault here?

 

[adespoton]

Regulator circuit for the battery? I'd start at the battery and walk your way back to the main board; the problem is going to be somewhere between the two.

 

[SuperSVGA]

Perhaps it is somehow getting shorted to ground at the power plug end. I've seen it happen with a bench supply that was not even outputting power yet, so somehow just physically plugging it in does it. I ended up installing a resettable fuse.

It even charges and shows battery charge correctly.

It does this after the fuse is blown? With the fuse blown it shouldn't be possible for power to get to the battery from the power adapter, though since the charge indicator is just from a switch in the power jack it may still think it's "charging".

 

[d3jsp]

I think that must be it! The plug is somehow shorting out the battery. Maybe a new charging port will help? Which resettable fuse did you end up using?

Yeah, it might be showing that it's charging because of the switch in the power jack. Though it's strange that it will still show a battery present and battery charge. Maybe from what it remembers in the PRAM?

 

[d3jsp]

Arg! This just happened again on another brand new portable M5120 that I acquired and recapped. This one would always have the charging status though, even when nothing is plugged in. Is it supposed to happen this often?

At this rate im gonna have to buy 2 fuses a day

 

[finkmac]

sounds like something is wrong with the batteries/psu you're using

 

[d3jsp]

Yup you are right. Can't believe I didn't notice this till now