AL-82

This could be the easiest mod I've come across.  This is only for the AL-82 but I believe it works with the AL-1500 also.  Open up the amplifier by removing what feels like 1000 screws.  Once the top is off and you can see the internals, look at the back of the band select switch on the front panel.  You should see a green wire going from the aux setting to the chassis.  Cut this wire.  Seriously, that's it.  Cut it and put the cover back on.  You're done.

The directions for this are in the manual, so I'm not going to go over step by step how to do this.  I just want to point out that it needs to be done.  I bought my amp second hand, and the tubes and chimneys were caked with dust.  Even if you haven't been using your amp in a long time, you should still be cleaning it at regular intervals.  Go clean it...