[Hallicrafters] SR-150 Audio Hum

[Mike Peron]

After installing fully checked tubes into both recently purchased SR-150s and after recapping the one PS that still had OEM parts, I took advantage of the on-going contest today to compare the rigs.They both picked up the same stations fine. The nicer of the two SR-150s has noticeably higher audio output at full RF gain. However, when I turn its RF gain down all the way I hear an annoying 60 Hz hum that goes up and down with its AF gain knob. The other rig on that same PS doesn't have the hum but neither the AF output (though still adequate ). The hum gets drowned out when the RF gain is advanced but still indicative of a problem I would say. I plan to align both rigs but before doing so would appreciate any suggestions you fine folks might have. Other than replacing tubes I have done nothing else to both rigs except a quick visual. Perhaps a dysfunctional audio section bypass cap ??

Thanks and 73's

Mike WB6UTW