Re: 4400/200 won't turn on?

[Michael <macallan%netbsd.org@localhost>]

Hello,

On Mon, 6 Sep 2021 14:26:22 -0400 (EDT)
Mouse <mouse%Rodents-Montreal.ORG@localhost> wrote:

> [Michael]
> > Check the onboard battery.
> > Older macs are notorious for not powering up with a dead battery.  
> 
> My port-macppc subscription seems to have gone away - or perhaps I
> unsubbed long enough ago I don't recall doing it.  I saw none of the
> above on-list mail.  I've got a resubscribe in progress; in the
> meantime, I'm replying by scraping the port-macppc archive.
> 
> I also got an off-list mail also recommending I check the battery
> (thank you, you know who you are!).
> 
> It took a little doing, but I eventually found the battery.  In the
> case of my machine, it's a small black plastic near-cube, connected to
> two pins of a four-pin connector (which has only three pins actually
> populated).
> 
> The battery was marked as being nominally 4.5V.  After removing it
> from the board, it measured somewhere between 1.4 and 1.5 volts (with
> my Fluke, a high-impedance voltmeter), so, quite dead.  Its markings
> gave me no reason to think it rechargable.

> I took a small external power supply driving 5V and connected it up to
> those pins, with a 1K series resistor because I'm paranoid.  Then the
> machine proved to be willing to turn on just fine, so the battery
> theory appears to be the winner.
> 
> I'm not sure what do here.  The negative battery connector pin has
> sub-1-ohm resistance to power supply ground, so I could drive the
> positive battery pin from the power supply's standby +5V line (probably
> with a capacitor to support brief power-off periods and resistors to
> avoid overloading the 20mA max).  But that would not survive long
> periods unplugged.

Most powermacs use a special type of 3.6V lithium battery, quite easy
to find even today. And for 4.5V I'd just use three AAAs and a little
bit of soldering & duct tape...

have fun
Michael