Re: GS battery replacement

[harold.h@genie.com (Harold Hislop)]

Brian H,

>> From: ronlouie@u.washington.edu (Ron Louie)

RWE|  I use three AA alkaline batteries in a RadioShlock holder; the
   | batteries stay external to the case, while the leaders are

>> Expected voltage is 3.6; your setup gives 4.5 unless you're using
>> NiCd batteries (and you aren't).  The system deals with the extra
>> V's OK?

Consider that the clock chip (also handles bram) used in the IIgs is
normally powered of the +5 line of the IIgs power supply when the
machine is turned on, and is powered by the battery only when the
machine is turned off. :)
 
Ok to go geek here... The IIgs +5 rail feeds a 1N914 diode (surface
mounted) and that diode feeds the clock chip. This means that the
clock really sees something closer to 4.7 volts. However the battery
(-nominal-) 3.6v also feeds the clock chip thru another 1N914 diode,
so the battery voltage is dropped to roughly 3.3 volts. [The diodes
form a 'wired OR' circuit, and isolate the two sources of power while
allowing the clock to be powered from whichever has the highest
voltage at any given moment. Much like the isolation diodes used
in the TrmPwr line of a SCSI chain]
 
IOW, using a 4.5 volt battery pack, instead of a stock 3.6 volt
battery will work just fine. :-)


--
-Harold Hislop
My comments are my own, if you don't like them then don't read them.
Apple II series hardware development and engineering services avail.