Bold= Fuse blown

[Waddy]

I recently bought a dual rec 3 channel amp, everything worked well except when I turned the back-switch from spongy to bold, the fuse always blew. So from there on I always played on spongy. Until our other guitarplayer bought just the same amp, with the difference that his amp also worked well on bold. And for the type of metal we play, the bold-type seems to sound a lot better. So my question is: Does anyone have any idea how come the fuse always blows every time I turn my dual to bold?
My other settings are: mostly the 3rd channel modern, tubes are 6l6 and mostly on silicon diodes. Thanks in advance, my dual is a second-hand, so it's kinda hard to take it to a store...

 

[Platypus]

Try switching it to bold before you turn the amp on.. does it blow then?

It's not supposed to blow for switching on the fly but I've seen it do it myself as well.

If it does it no matter what in the bold setting, try switching your power tubes for some fresh ones... how old are the power tubes? It could be that under the increased strain of this mode that you're pushing a dying tube too hard.