If you have a 2a adding a diode isn't going to make any difference. There are other things that could make it pop, like not having a permanent 12V supply, or having the permanent and switched 12V lines round the wrong way (if I remeber rightly)
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(list 6284, Mk1 S/N 00299 4GB blue [sold]. Mk2 S/N 080000094 20GB blue)