02-22-2013, 05:54 PM
Looking at the Rider ( http://www.nostalgiaair.org/Resources/784/M0013784.htm )info I think the 6AQ5 label is a typo. That label shows up on the views for parts locations but on the actual wiring schematic it shows a 6AQ6. A 6AQ6 is a twin diode-Hi mu triode while a 6AQ5 is a beam power pentode. The schematic is wired for the twin diode 6AQ6. You can check these tubes out at http://www.nj7p.org/Tube.php
As for the noise--have you changed out all the capacitors?
As for the noise--have you changed out all the capacitors?