Where's a hagiogolotre when you need one.
Do you really need to take the pa apart just to test the valves. Is there a
Jim Crow for this job, to avoid dismantling? plastic screwdriver to wedge
between valve and base ? long handled plastic pipe wrench to grab the
envelope, or some sort of suction cup to pull them out ?

In case its a safety issue. Owner does not know how it happened but the
plastic coating to the metal chassis around the IEC inlet is rucked from
partial melting? well it stretched back, as good as new, with low heat from
a hot air gun. Hopefully caused by such or an open fire. Unless the amp is
used with the speakers pointing to the floor then no convected heat from the
transformer, no sign of overheating of the Tx, and no sign of arcing or over
temp on leads,tags , IEC fuse , drawer etc- any known weird stock fault
leading to such internal localised heating.
No sign of any discolouring / pitting of the pins of the IEC , if it was a
bad IEC line plug arcing.