So anyway, it only took me two years to get round to sorting this out ... but I thought it would be worth updating in case anyone has the same problem. The bass was indeed wired incorrectly,
This: [url="http://www.ibanez.com/supportResources/wiring/2008/EQB_3B.pdf"]http://www.ibanez.com/supportResources/wiring/2008/EQB_3B.pdf[/url] is how it should be but the negative from the battery went straight to the bundle of earth connections on one of the knobs and there was an earth from one of the pickups that went to the switched part of the socket. Easily fixed with a soldering iron, amp is now powering down when unplugged so I'm looking forward to amazing battery life from now on.
Ed
[quote name='BanditSid' timestamp='1323970397' post='1469419']
Ed,
If the wiring has been "got at" it's possibly because the jack socket has been replaced but wired up wrongly. The black (ground wire) from the batteries goes to the inner ring of the stereo socket and is shorted to the socket ground by inserting a mono plug, as used on guitar leads, which then applies power to the pre-amp circuit. This allows the batteries to be disconnected automatically when the lead is removed, but won't work if a previous repair has joined all the "black" wires together,as the power will be connected permanently.
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