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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: nscaleworld on July 13, 2012, 09:16:46 PM
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I would like to do the CR2032 coin battery install in my Amiga 3000T. I was wondering if I could desolder and remove R192 and replace it with a 1N60 diode. Also, I noticed that there is both +5 volts and +12volts in this circuit. How exactly does the charging circuit work and can I remove it completely? I have to redo the zip memory, because I mixed up SC and PM zips, so I might as well take care of the battery issue too. The battery area of the motherboard is clean.
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(http://img88.imageshack.us/img88/9303/96948607.jpg)
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I hope that will give you some light on the problem.
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+12V is just used to avoid the voltage drop from the inline diode in order to raise the charging voltage, no need to worry about.
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I would like to do the CR2032 coin battery install in my Amiga 3000T. I was wondering if I could desolder and remove R192 and replace it with a 1N60 diode.
Yes, replacing R192 with a germanium or Schottky diode would work fine. Obviously the anode side goes to battery + and cathode (stripe side) to U190 pin 18. You won't need any other modifications than that when replacing the battery with a coin cell.
For a more detailed analysis of the entire battery and diode topic, read my posts in this recent thread (http://aoproxy.extropia.co.uk/forums/showthread.php?t=62053&page=2).
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Why is R192 there, what does it do? What parts make up the charging circuit and can they be removed?
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I believe the resistor is there to control the charge rate of the original NiCad. (The original charging circuit doesn't seem to have any means of detecting full-charge, but I don't know how important that is in this application.) It's useless when replacing with a coin battery and diode. While leaving it in place does little harm (referring to Castellen's earlier comments), it's a handy place to install the diode, with the benefit of being able to easily solder the 2032 coin socket directly to the board, and potentially a bit longer battery life with a Germanium or (better) Schottky diode.