Ashdown ABM Evo II

[sunshine_bassman]

Just recently bought an ABM Evo II for a backup amp, it was having issues cutting out that I narrowed down to a bad input jack. Replaced the jack, all was well. Played two gigs on it, and it worked fine. Played my third gig and on the second set it started cutting out. It would only cut out for a second, then come back. Sometimes it would just cut to half power for a few seconds and then come back full volume. Smacking the amp would help sometimes.
Is this a fried transistor? Protection circuit kicking in?

[g1]

If physical jarring has an effect on it, then it should be a connection issue. Bad solder, oxidized or loose connector, etc.

[Mick Bailey]

Check the screw terminals on the boards - they come loose after a while. The input and output level pots get really flaky - check these. A fried transistor stays fried and won't cut in or out with vibration. The FX loop contacts could be oxidised if it doesn't get used.

[sunshine_bassman]

It also will kick in when I play hard, it gets really splatty. I just remembered when my SVTIIIPro was acting like this, the bias was cold and that fixed it. Could that be the issue here as well? Is there a biasing method for these amps?