Clock won't keep time

[howardc64]

Mac Classic II capacitor replaced, boots up fine, sound works (was faint and then silent after I washed the motherboard), keyboard+mouse works, SCSI works. Battery also replaced.

It won't keep time after a power cycle. If I restart the computer, the time is kept there is no interruption in power.

Any ideas?

 

[howardc64]

New battery on the logic board shows 3.6V. Which chip is the real time clock? I guess I can do some continuity test and check if battery power supply reach that chip.

 

[register]

Does the clock run normally when the computer powered on? If yes, the clock chip should be fine.

Does the PRAM keep settings properly? If not, there might be something wrong with the battery connection.

If the PRAM setting are kept, the battery connection should be okay. Still there might remain a damaged wire to supply the clock chip.

Check also for unusual software or software settings. For example there could be a control panel called "Clock Adjust" which might cause unexpected results if not set properly. Could someone have put a program to reset the clock into the startup items folder? Consider to shut down and boot with extensions disabled.

 

[howardc64]

Thanks for the tip on problem isolation.

Clock does work when system is powered up. Mouse Tracking speed and Speaker Volume doesn't not survive power down. I'm assuming these 2 parameters are maintained by the PRAM battery.

So I guess likely somewhere between the battery and PRAM power supply connection. Anyone got schematics that might point out the traces I should be looking at?

 

[register]

Yes, mouse tracking speed and speaker volume settings are kept in the PRAM.

Before any further attempt to fix something you might consider to double check for proper polarity of the battery and also check if the battery is full. If the battery is of appropriate type, correctly inserted and full, most likely the battery connection is damaged somewhere.

As for the schematics I can not help, some other comrade might kindly assist. The off-load voltage of a battery might be a weak indicator of the charge condition. A suggestion to properly check the condition of a PRAM-battery would be welcome, too. Information about lithium batteries in general can be found on Wikipedia: Lithium battery, of course.