Re: Lisa won't turn on

The power button is illuminated when the power supply is operating, but there is no feedback from the light itself. eg. the Lisa will still work normally if the bulb is missing or burnt out.

I'd guess that a brief flash indicates the power supply is immediately shutting down.

One cause of immediate shutdown would be a problem with the I/O board which controls the power supply. As with your initial problem, this could be as simple as a poor edge connector contact.

If you hear a clicking noise from the power supply when you hold down the power button, that is normally an indication that the "crowbar" circuit is cutting off the power supply due to an overvoltage or overcurrent condition.

Overvoltage can be caused by power supply component failure or may be as simple as requiring adjustment due to changing the load eg. after changing the hardware configuration of the Lisa. Disconnecting/changing the 2/10 internal hard disk might have this effect.

Here are brief notes about adjusting the voltage: http://lisafaq.sunder.net/lisafaq-hw-pwr_PSU_adjustment.html

Overcurrent would likely be a short circuit caused by a bad capacitor in the power supply or some failure or foreign object creating a short circuit on a circuit board.

Generally, troubleshooting this sort of problem would begin with observing the +5 and +12 voltages at the I/O Board while the power button is pressed. If one is stuck at ground then check for a short circuit. If one surges over the nominal voltage then try adjustment and investigate potential component failure in the power supply. Also investigate the section of the I/O board circuitry that controls the power supply to see if it is telling it to shut down.

Let us know what you find - good luck!

>I'm having trouble getting my Lisa to turn on. The light on the
>button flashes for a second and then goes dark. I never hear the
>widget hard drive spin up. I remember reading that the bulb has to
>work or the Lisa to start?

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