[Amps] AL 80B Question

[Robert Carroll]

I have a very early AL80B.  It will produce 500-700W key down on all
bands--except 30m.  Of course you don't need much of an amp on 30m with the
limit being 200W, but I am  curious as to what the problem is.  The
suggested Ameritron tuning chart shows the load control at 0, which is
presumably plates fully meshed.  That indeed is where it wants to be loaded
on 30m, but it struggles to  put out 150w, regardless of how hard you drive
it.  Neither plate current or grid current is excessive.  The amp has a
30m/20m selection on the bandswitch and I get 700W out on 20m.  What would
the problem likely be.  Has anyone else run into this on 30m?  I bought this
amp used around 1995 and it has always had this behavior.

Bob W2WG