[Kenwood] TS950SDX: 50z hum on the audio

[jaking]

If you read the post, you will see there were also 2 standard kenwood
modifications,

If you read the post you will understand that a ground loop has been
discovered, and one should have to follow the methodology to find a ground
loop on any one of the many ground looped wires on the 950sdx. 
Start as suggested disconnecting the audio section, and progressively adding
higher up sections until the hum returns. The you have the offending board.
Then progressively disconnect connections off that board to you find the one
the hum occurs from.
You will find it. It takes time. For me it took about 8 hours, of
disconnecting ground wires, and reading and thinking about what to
disconnect next.

This was more than a suggestion: It actually worked, and made huge
difference listening to low volume signals, because the 50 hertz before
wiped out some of the signal, and you could just not hear that part with
comparable power to the 50 Hz power.




-----Original Message-----
From: kenwood-bounces at mailman.qth.net
[mailto:kenwood-bounces at mailman.qth.net] On Behalf Of Peter Ravn
Sent: Sunday, 3 May 2009 6:36 p.m.
To: Kenwood at mailman.qth.net
Subject: [Kenwood] TS950SDX: 50z hum on the audio

When the volume control on my TS950SDX is turned fully counterclockwise,
there is an annoying low level 50 hertz hum in my earphones. When the volume
is turned up on receive, the hum disappears into audio noise. If this was
the only problem, it was not woth bothering about. The trouble is, however,
that the hum is constantly to be heard while monitoring my own signal, using
my earphones.

Inspection has proved that the following measure suggested by Jeff King,
ZL4AI, on this Kenwood 950SDX page (
http://homepages.ihug.co.nz/~jaking/TS-950sdx.htm#_Toc193948223 ), has
alread been done. "Permanently removed 109-2-GND  form SW A  J/10 Connector
109. Soldered a 0.01uF disc ceramic capacitor to wire and another pi
connector and pushed this into Connector 109-2-GND. The otther capacitor
wire went to the removed  109-2-GND  metal female socket. This was covered
with insulation tape."

So what else can be done?

73 de Peter / OZ8CTH




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