A500 clock battery replacement
My little menagerie of Amigas got a workover last week. Some little nags that I wanted to fix. One of those was file modified dates on my source files ;)
So the Amiga 500/040 got a clock battery replacement like my living room A500/ACA500, an ordinary CR2032 coin cell that I bought at the local radio shop. In this case, the clock was on the trapdoor memory expansion, but this mod works on all Amigas and Amiga expansion cards.
Lithium coin cells like CR2032 are not rechargable. NiMh and NiCd are, and that's what Amigas are made for. Unfortunately, those are also the ones that will leak and corrode your electronics. The ML2032 is rechargable, but incompatible with the Amiga's recharge circuit.
Don't put hazardous batteries back in your Amigas, use a coin cell instead!
To use Lithum coin cells, you must add a low-leakage-current diode like 1N4148 and a 200 Ohm resistor between + on the battery and + on the board, like on page 9 of this PDF. A 270 Ohm resistor was the closest resistor I had that was >= 200 Ohm, which is fine.
This photo shows how I soldered one leg of the battery holder, then turned it and bent the + leg to rest on top a circuit, to be able to easily add the diode and resistor. The diode goes in the + pad on the board, the resistor I soldered to the + leg. Then I soldered them together. (The photo was taken just before I clipped off the unnecessary parts of the component legs.)
Now, this coin cell is protected and will last me years without any chance of nasty incidents. After that, I can just snap a new one in the holder!
A final note: If you're unable to set the time after swapping battery, type "setclock reset" in CLI/shell.