this is an interesting tit bit that happened here, this older piece of forgotten amp history the Laney PL100 had a hidden but nasty surprise inside that kept the amp from its true performance
the dropping resistors to the preamp board are mostly the wrong value and the voltage being fed from the power supply was not being handled correctly. in short the two 5 watt dropping resistors were heating to scorching temperatures. together with using the wrong value resistors the final feed voltage to the pre board was too low. I researched the thing and it was a well discussed issue and one person actual designed a new supply as part of turning it into a standalone Preamp.
my conclusion was to get the resistors off the board and substitute " 10 Watt Power Resistor Metal Case" and to chassis mount with compound. the pictures are below and boy did that work all the way around. the amp needed several other parts but this was the main issue and for anyone out there with one this should be done.
locating the new resistors
a few connection mods and
dont try this