Macintosh LCIII start up failure

[J.Stock]

I’ve got a dead Macintosh LCIII at home. It still turns on but it doesn’t boot up. The fan and hard drive both switch on and start spinning around however nothing else seems to operate. The crystal timers in the machine are receiving between 0.40 - 0.10 volts of power.

There are no capacitors that are damaged or leaking in the computer tower. I’ve also checked the power supply and there are no leaking or damaged capacitors in the power supply. In-fact everything looks just fine. Someone running a computer store told me that there could be an issue with the microchip processor (VLSI chip) in the computer.

 

[Anden Selmani]

replace the capacitors they are bad

machine will also not turn on properly without a good battery

 

[Elemenoh]

Can you share some good photos of your logic board? Even if you're not seeing obvious signs, the caps may have leaked onto other components, causing a short. Replacing them alone might not solve your problem. You might have to clean the board thoroughly and potentially repair broken traces.

Have you measured the voltage rails with a multimeter? It'd be good to know if you're getting a solid +5/+12 V at the hard drive connector. Ideally you'd recap the PSU regardless, but if the rails check out okay you can at least more confidently rule out the PSU as a problem.

 

[Volvo242GT]

Sounds a lot like what user c00gr on the 68kMLA is experiencing with his LCIII...

Performa 450 restore / no chime

Hey folks… picked up a Performa 450 at an estate sale and the board was a bit grungy with leaky caps, but otherwise in decent cosmetic condition. PSU voltage looks good, fan spins, HD spins up, but then no chime, and then the HD idles. Recapped the board as well, checked traces around the caps...

68kmla.org

 

[joshc]

machine will also not turn on properly without a good battery

This isn’t true for the LC III, it works fine without a battery.