[Hallicrafters] HT-32 hum

[Misic, George J.]

Peter,

Other than needing new filter caps or a tube [probably in the audio
amplifier functions] with a filament-cathode short or high leakage, the use
of solid state rectifiers may cause a rise in the hum from the rectified DC,
since the solid state diodes have much lower series resistance than the old
tube rectifiers.  This can cause a higher charge current at the peak of the
AC sine wave from the 60 Hz line [120 Hz hum, as they are full wave
rectifiers].  If the filter caps are good, a bit of series resistance in
series with the rectifier diodes may help.  22 ohms at 2 watts is probably a
decent value.  73.

George KE8RN

-----Original Message-----
From: psturdivant n1ps [mailto:sturdivant at adelphia.net]
Sent: Monday, February 17, 2003 6:57 PM
To: Hallicrafters List
Subject: [Hallicrafters] HT-32 hum


I have a HT-32 that has had an issue that I have put off.  It xmits some
noticeable hum when transmitting in DSB (AM) mode,  I have had enough
complaints about the hum....not very much...but it can be heard.

The hum appears with NO mike connected or with it in.

I'd like some opinions on the cause of the hum for anyone that has either a
32 or a 37.  It could possibly be the filter caps.  I have not looked at the
B+ or HV lines with a scope as yet and the previous owner replaced the
rectiflyers with solid state.

TNX

Peter
n1ps

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