Macintosh Portable (backlit) battery voltage requirements

[Mr. Macintosh]

Hello all,

It’s been quite a while since I’ve posted here, and it’s good to be back! I had a quick question for you Portable people out there: I just recently recapped a clean-looking backlit model, and it seems to be working fine off of my bench supply running at 6.8v. The problem is, lowering the voltage to 6.7, 6.6, or 6.5v makes booting either hit-or-miss or impossible.

Also, I bought a new 6V 5Ah SLA battery (not the cyclon pack) to power the system. Even after being charged up to its max of 6.6V, while connected to the original charger, the machine refuses to boot completely. Sometimes it gets farther on just the battery, but never all the way.

I guess my question is this: is this normal for a backlit Portable? Is there some difference in the Cyclon battery that would bring it within spec? I would imagine the system should function properly at 6.5V given it’s designed to run for hours. Any insight is appreciated. Thanks guys!

 

[techknight]

No this isnt normal.

Open up the battery meter widget and see where it sits at certain voltage levels when you lower it. 

You probably have another power regulation/op-amp victim. VERY hard to track down and repair the issue. 

 

[Mr. Macintosh]

Thanks for the reply. I tried varying the power supply down to 6.6V, and it says the battery is full at every voltage. At around 6.6-6.5V, heavy HD activity will freak the system out, but it’ll still run if I lower it from 6.8 down to 6.5 after I boot.

 

[techknight]

So you need to monitor the 5V regulator. Should be roughly 5.2V. if its falling below that when your input voltage starts getting around 6.8V you have op-amp and/or voltage reference trouble. 

 

[Mr. Macintosh]

Hmm. I’ll have to check on that. Would it be in the cluster where the hybrid chip usually is?