[Hallicrafters] SR-150 Audio Hum

[Tom Burke]

Sure, you guy's are fixing up your Hallicrafters and I'm still stuck.

Does anyone have a clear readable schematic for a National NC-270?
Everything I can find from the web is blurry and unreadable.

Thanks...

Tom Burke

-----Original Message-----
From: hallicrafters-bounces at mailman.qth.net
[mailto:hallicrafters-bounces at mailman.qth.net] On Behalf Of Mike Peron
Sent: Sunday, November 20, 2005 8:53 PM
To: hallicrafters at mailman.qth.net
Subject: [Hallicrafters] SR-150 Audio Hum

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
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