Mauri says: >some tubes mechanical construction (internal electrodes or wires, socket >dimensions and shape) lead to inherent stability problems Very true! 572Bs are amongst the worse. 73 Peter G3RZP -- FAQ on WWW: http://www.contesting.com/FAQ/amps Submissions: amps@contesting.com Administrative requests: amps-REQUEST@contesting.com Problems: owner-amps@contesting.com