Tuesday, 20 August 2013
In my experience, these fuses can and do fail, but never (so far) when the carriage is actually in use.
The first situation is where the power is on and the tip of the DC connector is allowed to touch metal (for example, various parts of a knitting machine!) This is why instruction books give a very specific sequence for connecting and then powering the equipment. The reason is that the tip is not recessed, as it probably should be, creating the potential for a short circuit. So, if you don't like playing with fiddly power supplies, be careful.
The second situation is where the machine is left plugged in for a period while out of use. This turns out to be because of a process called 'electromigration' which you are welcome to look up here if you wish!
In both cases, the fuse has to be replaced and this is thankfully fairly easy.
The holes may be sealed with small rubber plugs which can be rooted out with a small crochet hook or similar.
Then the screws can be taken out with a long-shanked crosshead screwdriver.
Replace the fuse (on the circuit board near the output cable).
Reassemble. Job done.