SAFETY
Very high voltages are generated inside the casing, around the cathode ray tube.
Before opening the casing of the computer switch off and leave for a few minutes
to allow static charges to leach away. Then remove the electric plug from the
mains socket. Even then, high voltage static charges will remain for a time
which can administer a shock. Whilst such shocks are unlikely to cause injury
they can be unpleasant and are best avoided, so I recommend that the machine
is left for at least an hour, preferably overnight, after disconnection before
removing the casing back.
METHOD
Remove the printer, keyboard and any accessories connected to the expansion
port. leaving the unit bare. Place a folded towel or similar soft cloth on a
working surface and lay the computer face down on it. Remove 6 screws from the
back and sides and place in a safe place. Remove the two small knobs from the
side of the case; they simply pull off. Carefully lift the back off. You may
need to insert a knife blade in the joint to start it, but it should lift off
easily. If not, find out why before proceeding.
Turn the machine right way up and examine it. Just below the tube is the power board, and beneath the power board is the CPU board and drive(s). These latter are screwed to the lower part of the casing which must be separated as a unit from the upper casing in order to access the drive(s).
These machines come in various layouts, so only general instructions can be given. It is recommended that notes and sketches be made whilst dismantling to ensure that all connections are remade correctly. In all cases that I have encountered plugs and sockets have been colour-coded, or marked or will only go on one way.
Unplug all cables which connect the upper and lower case. Smaller 4 or 5 pin plugs are usually colour coded and will only assemble one way. They have a security clip which must be held back whilst unplugging. Try to pull on the plug not the wires. They should separate easily; if not find out why. Where there are larger type plugs they are often rather tight and should be prised apart with a wide screwdriver blade or something similar. Don't try to use brute strength or you may do some damage. Finally disconnect all the black and yellow/green wires by unscrewing from the sides of the power board.
Place the monitor face down on the soft cloth again and remove 4 black large-headed screws on the steel angle plates which hold the upper and lower parts of the case together. Carefully separate the lower part, checking that no connecting wires remain. There is a lug on the casing at the front that can make it awkward to separate the casing; it's a bit like a chinese puzzle. Just as you're ready to give up the casing will fall apart, so persevere.
Lay the lower casing on the table and remove the screw which secures the black wire and the end cover of the drive and remove the end cover. Remove 4 screws which secure the drive and remove the 26 way data cable and the 4-pin power plug. There is a security clip which must be held back before the power plug is released. Note which way the data cable is connected. The coloured wire is usually towards the power plug, but check it.
Fitting the replacement drive is done by reversing the dismantling procedure. Connect the drive and screw it in place. Replace the drive back cover and black wire. Reassemble the casing with the four screws and replace all the plugs and wires. Have a good look around before replacing the back for testing. Take your time and make sure everything is OK. Don't try to force anything. The back can be difficult to replace sometimes but patience will be rewarded. It only remains to plug in the keyboard and try the machine. Always use a spare disc if available to test a drive, never a valued one, or at least open the 'write protect' hole. It'll probably be OK, but .............
What if it doesn't work Unlikely, if you've followed the above instructions. I've supplied a lot of drives and have had few problems.
The most likely causes of trouble are the power and data connections to the drives. If the drive won't run or the red light doesn't glow, then suspect the power connection. If the machine won't boot then check the data cable(s). Either an A: or B: drive wrongly connected will prevent booting. Unplugging and replugging will sometimes cure a fault. If a drive is connected the wrong way round, it won't damage it, but will obviously prevent it working.
Switch off and remove the wall plug before touching anything, unless you are experienced. NEVER DISCONNECT OR RECONNECT ANYTHING WITH THE POWER ON. This can damage the machine or you or both.
Ron King
e-Mail address........ron@king27.freeserve.co.uk