[Hallicrafters] SX-62 Run 2 overhaul

[Mark Shaum]

----- Original Message -----
From: "Phil Atchley"
Subject: [Hallicrafters] SX-62 Run 2 overhaul


seems the first two RF amplifiers are dead. Probably a capacitor as it
plays
much better if I attach the antenna to the 3rd section of the tuning

Any "gotcha's" to watch out for in this receiver while I'm working on
it?

---

Both RF stages are not active on all bands. Watch out for any signs of
B+ leaking from the plate of one of the rf amps to the grid of the next
stage.  This could be the dreaded "SX-42 bandswitch leakage syndrome"
but I do not believe the SX-62 series is as prone to this painful bug.
If you see any sign of postive voltage with a VTVM or other high
impedance voltmeter on an amplifier control grid start looking for a
leakage path, be it in a capacitor, switch or shorted rf transformer,
etc.

Your manual should have a chart with "approximate" voltage values for
each pin of the tubes.  Measurements should be in the same ballpark
values as the manual calls for.  If measurements are low, look for
something leaking to ground.  Wrap a temporary lead around the pin of  a
tube and check from the top of the chassis if you cannot reach the tube
socket with a probe.  I recall the "front end" of the SX-62 was not the
easiest place to reach for probing or component replacement.

My first SX-62 had leaky screen bypass capacitors in a couple places as
well as a some cathode resistors that had increased in value several
hundred percent.  These all contributed to lower gain for each affected
stage.  I also had some leakage in capacitors that ran from the AGC bus
to ground, causing some distortion on high level signals.  If the SX-62
had an s-meter I would have bet it would have read low until these were
replaced.

It might be some work but a SX-62 is worth restoring.  Mine still plays
every weekend when I'm in the shack, even if just to monitor the local
AM broadcast news.  The SX-62 and R-42 combo probably has a better
frequency response overall than the transmit audio of the station they
are tuned to, but that's life in today's AM broadcast world.

73! - Mark K9TR