Shane Shariff said in comp.sys.amiga.hardware on 30-Jul-96 18:34:17
SS> my internal clock seemed to die on my A3000. It seems that
SS> no power is getting to the clock chip, and no power
SS> goes to the clock battery to recharge it...
SS> Does anyone know which chip is responsible for charging the battery?
SS> Also, any ideas on powering the clock chip itself, with say
SS> a lithium battery, so at least it doesnt lose the time?
SS> Any help is much appreciated!!! (I am tired of setting the clock
SS> ( it looks like the motherboard may have been slighty damaged
SS> in this area from corrosion but its very little; some resistors
SS> have a bit of green stuff on there leads..)
This info I've pulled from my A3000 service manual (note: this manual was
printed for some version of the motherboard BEFORE the rev 9/x motherboards.
Some items are different on my 9/something motherboard):
The Clock/BattMEM RAM battery (BT190) is charged by two resistors (R190 and
R192, both 470 ohm) and a diode (D191, 1N4148). The power is supplied from
the main +12v supply thru R190 to D191's anode and then from D191's cathode
thru R192 to the battery + terminal. There is also a connection to +5v
supply from between R190 and D191 through another diode (D190, 1N4148). The
power for the clock chip is pulled from between D191 and R192. Since both the
clock and the battery appear to be losing power, I'd first check to see if 12
volts is present on the powersupply side of R190. If so, then R190 and/or
D191 may be blown. Another possibility is the battery could be bad, with a
dead short to ground, which may pull the voltage down far enough between R192
and D191 to keep the clock chip from working.
I've repaired electronics for about 6 years at a local shop, and have seen
those types of problems in CD players, stereos, etc., so if you need anymore
help, let me know.
Amiga 3000 '030 25MHz, 4 meg FastRAM, 1 gig HD, Zip drive, AmigaDOS 3.1
and..... *Vision 64 2 Meg video card
Public PGP key available, Fingerprint = A452EF542E7FFD29 E58E374FFB7AA881
"Dead or alive, you are coming with me." Robocop