Hello Amiga fans,
I was an old Amiga user and have resumed my old hobby.
I have an Amiga 600(HD) and recently got the A601 expansion board with 1Meg of ram.
The extra 1MB works fine but the RTC (real time clock) does not! I opened the metal casing and discovered, surprise, battery leak. I removed the old 3/V30R flat battery pack and after a bit of cleaning up it looks like the picture in the following photo album:
A601 battery leak board pictureApologies for the non crisp quality but that's as good as my tiny camera will do.
By looking at the board I thought that the corrosion has not affected the R913 or C9 or C913 next to it.
Unfortunately I was not able to find a proper schematic of the A601 but I have looked in the A501 schematic (a relevant picture of which is also found on the web album link posted above).
After replacing the battery with a new one fully charged the RTC would still not work.
So I took my trusty multimeter and checked a few things:
1. The line going from the positive pole of the battery delivers power just fine to the left side of the R913 (resistance 0)
2. The negative pole of the battery gets connected properly to the ground circuit.
3. The negative battery pole and pin 12 (GND) of the M6242B connection is fine (resistance = 0)
4. Without the battery on the circuit, checking between the + and - receptors I get a 1512 Ohm resistance reading
5. Same reading I get when checking between the pin 24 (VDD) of the M6242B and the + battery pin on the board (1512Ohm) :-)
6. Finally, because I only have high school knowledge about electronics, I also checked the resistance between the two pins of the C9 small capacitor and the C913 barrel-shaped capacitor. In both cases I get a reading of 21 Ohm.
Of course I realise how a capacitor works and checking it's resistance does not really make sense but I don't have any other tool.
7. Pin 24 (VDD) of the M6242B and any point in the ground circuit shows up 21Ohm !!!!
Summing up, the issue is that if I check the resistance between the + and - receptors for the battery on the board I get a 1533Ohm (notice, it is equal to 1512+21) reading. That, with the battery connected, drains it overnight.
Any idea as to which component has failed, where is the short circuit or what else to check?
P.S.
Forgot to mention that WITH or WITHOUT the battery connected setclock reports battery backedup clock not found