Power button no longer boots up Mac?

[Syntho]

I have a 9600. For some reason when I first got it a while back, pressing the power button would boot the machine. Now it doesn't work. Why?

 

[Macdrone]

Pram battery ?  Power supply caps shot?  Capacitor on motherboard?  does keyboard power on work? (that would mean plastic or button is broken)

 

[max1zzz]

I would also cheack the button with a multimeter, the button on my 8600 got destroyed by the previous owner, still haven't got around to replacing it

 

[Syntho]

I've got an extra PRAM battery laying around, brand new. The button works when I'm already booted but it won't power up the machine.

I remember posting a thread about using an SVHS cable as an ADB extension cable and someone mentioned something about it possibly draining the PRAM battery. That couldn't be it, could it?

 

[Byrd]

Those 8x00 and 9x00 tower case buttons can fail over time, they usually get budged off the PCB and need resoldering.

ADB = SVHS pinout, wouldn't do anything sorry!

 

[Syntho]

God I'm an idiot. I meant to type the KEYBOARD power button in the title. The normal power button is A-OK.

 

[noidentity]

ADB does use a separate line for the power key, so if that line isn't connected well the keyboard could still work normally and have no problems, and even the power key properly bring up the "Shutdown?" dialog once the machine is booted. Does the power key work reliably once the machine is booted?

 

[Syntho]

The power key functions normally when I'm booted up. I remember when I first got the machine that it was great to be able to start it up by hitting the power key on the keyboard. Doesn't work now for some reason unless I'm already booted and I want to shut down.

 

[Syntho]

Just replaced the PRAM battery. Didn't help.

 

[markyb86]

Could be a bad SVideo cable.

My G3 boots fine from the keyboard when plugged in directly, but I have it plugged into a KVM switch, and it won't boot that way anymore.