pulling the power tubes is going to raise voltages in the preamp and the filter caps should be rated for the increase. but pulling the power tubes should render the power amp section dead, but if it is not shunted to ground it can produce noise with some of the components still "in circuit". a schematic is always helpful when seeking advice on do's and dont's of the gear in question.
"Tone is in the instruments. Technique in the hands. Do what you will." ~ quote from some guy at the TGP forum