Macintosh Portable

For testing my Macintosh Portable I have connected an external 6V battery with new Pram Battery but not the Power Supply. Be careful to connect the positive pole on the positive pole and negative pole on the negative pole because there is no protection.

Wow, for a second I thought new as in brand spanking new. That would have been crazy.

You will want to pull the mobo and clean it. I have yet to see a portable that did not leak caps. In fact a few had wet spots on the mobo from gap leakage! The only board that did not was a new board I bought.

i like the hand made pcb for the 34 to 50 pin scsi adaptor!

Wait so I'm looking here and I see your m5120 but in a pic it looks like it has a backlit screen but doesn't have a backlight upgrade kit. Or, am I see thing?

There are pics here from two different users. The lower being backlit machine. Or am I mistaken in what you are seeing Hap?

Explains it

That sorta looks like my test setup, but much crazier in the event I am using a benchtop adjustable power supply. 

@uniserver: I have made this hand made 34 to 50 pin scsi adaptor because the previous owner had destroyed the HD connector.

@haplain: effectivly @mactjaap Macintosh Portable is a M5120 (non-backlit) and mine is M5126 (backlit) but everything else is the same in M5120 and M5126.

@techknight: When I did this test, I had only an external 6V battery on hand but it works perfectly.

Mactjaap can do a test with an external 6V battery or an adjustable power supply.

Thanks matacao.

I have a 6v 1000mA adapter. Would that work too?

6V would be work but I don't know if 1A is enough.

Edit: Original battery are 3x 2V 5.0 AH (Cyclon) --> 6V 5.0AH, I think that 6V 1A power supply can match.

Trickle charge the original lead acid battery. 30 minutes on charge, 30 minutes off. Use a meter to check voltage across the poles to see if it is charging. Repeat for six hours. Is the battery recovering? Is it taking a charge? I think I wrote about this years ago on 68KMLA, so try a search.

1A is not enough. You need about 2 amps

OK! I'll have top wait. I do not have 6V 2A in the house. 6V 1A is the best.... to be continued.

What about 5V 2A? Will that work? Thats what I can deliver. If not I will buy one with correct values.

For a correct operation I think that 5V will be short. 

I gave it a try with the 6V. Also attached a 9V PRAM battery. Nothing. Absolutely nothing happens. So, I will try definitely a 6V 2A one.

For my test, the Mac have started after 10 minutes

Cant use 5v. Undervoltage lockout kicks in at 5.7v

Undervoltage lockout? I didn't realize that was a thing... but guess it makes sense. Would explain why I've read about some old Macs giving a Sad Mac when they're started with not enough power.

Thats not the same thing, your comparing apples to oranges there. 

Undervoltage lockout is designed into the circuitry of the macintosh portable. After it falls below a certain point, the window comparator latches and releases the 5.2V logic voltage from the rest of the system. It will not power on. 

My main concern for now is this:

First I would like to know if the motherboard is working. Then worry about the rest. Could there be some live with 6V 1000mAh or should I really buy a 2000 one?

Yes, but it wont start. Soon as you try, itll kick in the overcurrent on the 1A adapter.