Switch off first !!

 A good spec Pentium II computer arrived on the bench the other day. The owner, after plugging in a PS2 keyboard, could no longer use either the keyboard or the mouse port.

There's a warning in Windows, seen if you start up a computer without a mouse to the effect that you must switch off your machine if you need to plug in a PS2 mouse. The PS2 connector carries 5 volts and because the pins are pretty tiny and the connector locating method is fairly flimsy, a short can result if you insert a keyboard or mouse plug the wrong way round. The result is a blown fuse or burnt track on the motherboard together with potential other damage.

In this case we tried an old USB keyboard with a PS2 mouse socket fitted to the rear. This worked until we attempted to fit a new keyboard when things started to go wrong. Eventually the motherboard wouldn't boot up because the BIOS EPROM seemed to have developed a fault and later testing of the 32 Mbyte memory DIMM showed this to have expired also.

All was not lost however, a new motherboard, a faster, more modern processor and a new DIMM saved the day! The cost of these was a better bet than finding a new motherboard into which to install the old working bits.

Be warned. Plugging a PS2 device into a box with a mains plug attached doesn't always result in a catastrophic fault but when it does it can be quite painful on the pocket. On the other hand, looking at it philosophically, it's a good excuse for upgrading!


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