Fuse blows when amp is moved - Ideas?

[BenH]

The amp - Fender concert II , with some added mods.
The problem - Left in the reheasal room the amp has no problems, but at the last few gigs on arrival, the amp blows the second fuse when standby is flipped to on. The amp has been moved cold to the gig. Put in a new fuse, everything is fine. After the gig move the now warm amp back to the rehearsal room, come back a few day later, switch it on, dead fuse . Change fuse , every thing is fine for weeks until the thing is moved again.
Any ideas as to what might be causing this phenomina ?
Ben.

[TweeDLX]

Hi Ben,
You must have taken the chassis out and shook it/vacuumed out any stray solder chips? Looked for a loose wire or cracked resistor? I know these are stupid suggestions, but sometimes the simplest things...you know. I have a Mackie powered mixer that occassionally loses one channel after it gets moved. A good shake "fixes" it. You almost have to figure it's something that can move (or vibrate) when the amp gets moved. Good luck! I imagine your guitarist is really whining now... :D

Mike

[Structo]

Could be a cold solder joint, loose connection.
Or maybe after the mods the tech did not secure a component well enough and it is moving and touching something shorting out.

[drgonzoguitar]

Make sure you are using Slo-Blow fuses. A fast acting fuse can blow when turning an amp on.