Real time clock installation instructions for Amiga A4000D
Fitting and testing a replacement Ricoh RP5C01 real time clock IC to an Amiga A4000D Anthony Hoffman June 2008
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Power off the computer, disconnect all cables and move the computer to a brightly
illuminated desk to be able to work on it.
Lift the top case by removing the two screws in the rear upper corners which will
allow the case to slide backwards slightly, then upwards.
Locate the real time clock, U178, which is on the outer edge of the main board, close to the
joystick connector and just to the side of the memory slots. You may need to remove some or all
Zorro expansion cards to be able to access this area of the main board.
By default the clock is soldered into the main board, though your main board may have been fitted
with a socket. Replacing a soldered in device is not covered by these instructions, only replacing
a socketed device is described here.
If an existing clock requires removal, use a small flat blade screwdriver between the underside of
the clock and the socket, working from the two narrow sides to gradually lift the device from the
socket.
Before fitting the new clock, ensure none of the pins are bent, and all the pins are pointing
vertically downwards.
Carefully press the new clock into the socket, making sure the polarity is correct, as shown below
Battery
not shown
Real time clock - U178
Caution! The computer main board contains devices which can be damaged by static electricity
discharges. Use an anti-static wrist strap connected to the metal chassis of the computer
or touch one hand to the metal chassis before touching any component on the main board.
Notch indicates
device polarity
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After fitting the new clock, check that all pins appear correctly inserted into the socket. Check
again that the polarity is correct. The small notch at one end of the device should be closest to
the rear of the computer.
Check there is no corrosion around the real time clock battery (BT176). Any corrosion will appear
as a white powder or crystals around the ends of the battery. A leaking battery may cause a
green or blue coloured surface to form on surrounding component legs and solder joints. If any
corrosion is evident, the battery must be removed and replaced immediately.
Refer to this website for further information: http://amiga.serveftp.net/battery.html
Before reassembling the computer, connect the keyboard, mouse, monitor and power cable to
test the clock operation. You may need to re-fit some or all Zorro cards to allow the computer to
boot normally.
Power on the computer. If it does not boot normally, power off and check all cables are correctly
connected.
Run the Time Preferences program, located in the System
(or Workbench) preferences drawer; SYS:Prefs/Time
A new clock should default to the date of January 1
st
1978.
Set the current date and time then click on the save button.
If the save button appears ghosted (greyed out), it indicates that the system cannot see the real
time clock. A common cause of this is damaged components and/or circuit board due to battery
corrosion. See this website for more information: http://amiga.serveftp.net/RTCrepair.html
Power off the computer for 5 minutes. Power on again and use the Time Preferences program to
check that the time and date have been retained, and that the time shown is the exact time of
day.
Power off the computer again, reinstall any Zorro cards and reassemble the case. The job is
complete.
Any questions or problems, feel free to Email me: ahoffman@clear.net.nz
Note:
Do not adjust the clock trimmer capacitor, VC190. This is for accurate adjustment of the 32.768kHz
oscillator, which requires a frequency counter to calibrate correctly. Adjusting this capacitor incorrectly
may cause excess clock time drift.
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