[Hallicrafters] S38C - FADING

[Patrick A. Thompson Sr.]

When you state that the "AF side of the set seems fine", do you mean that if
you turn the volume control well up you hear hiss and slight hum? Or do you
mean that band one (standard broadcast) is okay but the shortwave bands
fade? Did the S38C have an input for a phonograph?

The behavior of the pilot lamp you described sounds normal so your
conclusions about the filter caps are probably correct.

Slowly dropping sensitivity implies a component is changing value as the set
warms. Unfortunately, the component could be a capacitor, resistor or more
unlikely but still possible a tube.

I don't have an S38C but do have its cousin an S38E.  My S38E had several
tubular capacitors that were leaky. Most were black plastic colored coded
with stripes similar to resistor color codes. Those caps are in my opinion
the most failure prone component in the receiver. Other gray colored plastic
cased tubular caps were also leaky.

With schematic in hand and good notes those caps can be replaced in one
evening.

Slowly increasing leakage through one of these caps could be biasing off one
of the radio's tubes causing a slow fade.

I don't know your level of expertise but beware that the S38 series may have
one side of the chassis hot or directly connected to line voltage and
present a shock hazard. The US models need to be serviced with an isolation
transformer.

Pat
wa4tuk

-----Original Message-----
From: hallicrafters-admin at mailman.qth.net
[mailto:hallicrafters-admin at mailman.qth.net]On Behalf Of Jim Welsh
Sent: Sunday, March 07, 2004 11:03 AM
To: Hallicrafters
Subject: [Hallicrafters] S38C - FADING


Hi

My recently "restored" Hallicrafters S38C worked weel for many months,
however, it now starts up OK but then fades to silence - see the following.

The AF side of the set seems fine and does not "participate" in the fading.

On start-up, the panel light glows bright, then dims, then comes up to a
useful brightness, the set plays, then fades. The band-switch has been
cleaned, ditto the others.

A while back I replaced the main power capicitors, so I do not think that
they have much to do with the problem.

Any help (on or off the reflector) would be appreciated.

Jim Welsh
Johannesburg
South Africa



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