[Hallicrafters] SX42 restoration notes

[Al Parker]

Hi Joe,
    That's a great report, thanks for the info.  Maybe that's why my SX-42
seems so lethargic.
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info

----- Original Message -----
From: "Joe " <jhanulec at mail.portjeff.net>
Subject: [Hallicrafters] SX42 restoration notes


> After changing all the wax coated paper capacitors and all the out of
tolerance resistors the radio still lacked gain even though all the IF and
RF coils peaked.  All the tube voltages measured nominal so I tried
replacing the mica capacitors in IF can T3 which seemed to be most
deficient.  The improvement was a surprising 10 dB at 455 kHz and 6 dB at
10.7 MHz.  After changing capacitors in the other two IF cans, the receiver
become "alive" and a real performer, even though I didn't pick up as much
gain with T2 and T1.  The mica caps that were removed didn't measure any
leakage on a 20 Meg scale so I can only assume that the ESR was the problem.
Apparently the ESR was't bad enough to show up as inability to peak the
tuned circuits.  The 455 kHz coils are very delicate and made up of very
fine litz wire, don't break any of the leads as I did.  I used CM05 mica
capacitors for the replacement.
>
> Now I'm close to the specification of 60 uv for S9 at 14MHz.  I say close
because the S meter which is speced at 5 ma FS actually is almost 7 ma FS.
Does it need a magnetic jolt?
>
> The receiver is a delight to use on both AM and FM especially with the
sweet audio from the P-P 6V6's and R42 speaker.
>
> Now I need to do the same on my SX62 which has low FM gain.
>
> Joe Hanulec