Amiga 4000 battery problem

[Castellen]

For a start, try erasing the non volotile memory in the real time clock using this program:
http://amiga.serveftp.net/MiscFiles/RestartClock.lha

If that doesn't clear things up, you may have a hardware fault, like open circuit data or address lines going to the RTC.  It would seem unlikely all of the boards have the same hardware problem though.

Refer here for repairing the RTC, it's basically just a lot of continuity checks:
http://amiga.serveftp.net/RTCrepair.html
http://amiga.serveftp.net/Battery.html

Failing that, I'd suggest replacing the RTC data latch, U177 (U195 in A3000).
Instructions are aimed for the A4000D, but the A3000D uses an almost identical circuit.  Component references will be different.

Don't touch the "small screw" (trimming capacitor) by the RTC, this is used to set the crystal frequency to exactly 32.768kHz.
You'll need a frequency counter if you want to set it, or lots of trial and error adjustment.

[Castellen]

Without seeing it and testing the board myself it's impossible to say exactly where the fault is.

Refer to the RTCrepair link I posted above.  I'm assuming you don't have a logic analyser handy, so in that case it's just a matter of testing each of the PCB tracks for continuity.  All you need is an ohmeter/multimeter.

Failing that then replace the 74HC174 data latch, and failing that, replace the real time clock IC.
Most of the time it's just a PCB track open circuit and/or a dead latch, both of which are easily fixable.
The RTC ICs are becoming hard to get, so with a bit of luck it's not that.
As circuit is not very complicated, it's no big deal to get it going.


I'm planning to update the repair pages sometime over the next few weeks to make them a bit easier to follow, add some more info, and try to make the layout a bit better.