I have a problem with my amp. Its a Hughes and Kettner Warp7 half stack.

The problem is that it keeps fading out when i play, doesn't cut out just fades to the point it sounds like its on at low volume.

Then i play for a bit and the sound fades back into full volume, which is why i thought it could be a power shortage limiting the amount of power that goes into the amp as i live in quite an old house.

The fuse in the amps plug is a 10A fuse/or a 5A fuse if i switch to my other plug, is the fuse the right size for a 230V amplifier?

I have tried changing all the other cables, except the head to speaker cable and its not my guitar either.

Any suggestions?

SQ Custom 1, Washburn G-JRVs x3, Yamaha ERG121C, Samick Interceptor, Encore Acoustic, Vintage 5 String Bass, Unbranded Red Bass.
Line 6 SpiderII Halfstack, Laney/Carlsboro Halfstack.
Crybaby,Whammy,Flanger,Stage Tuner,Tremolo,Bass Overdrive