[sdiy] Calling Harry or some of you knowing old hardware..

[Jean-Pierre Desrochers]

> A series thing that is a.... battery or..capacitor with uneven length 
> plates on the schematic.  With B.C. written by it.

Sounds like this could mean 'Blocking Capacitor'.

> short one side of the device away from the grid, little difference. If I 
> short the side on the control grid then it totally eliminates the hum 
> noise.

This device could have lost its caracteristics and has gone
'too much high impedance' this results like a floating wire
connected to this probably very high gain, high impedance input(?)
So when you connect the 6SJ7 grid side of this device
to the ground you completely eliminate the floating wire effect
and drop down the actual input impedance to zero cutting
any noise.

Just my thoughts..

J-P

----- Original Message ----- 
From: "Bob Weigel" <sounddoctorin at imt.net>
To: "synthdiy" <synth-diy at dropmix.xs4all.nl>
Sent: Friday, August 31, 2012 5:39 AM
Subject: [sdiy] Calling Harry or some of you knowing old hardware..


>I was working on an old Knight unit...probably the first DJ unit.  lol. 
>Turntable on a metal box that uses 6SJ7 preamp tubes that get quite noisy 
>when I turn volume up.  I eliminated the power supply cap by putting in a 
>huge one which did help some but not much.  Very quiet now past the volume 
>controls..very simple circuit there.  Except... these strange parts on the 
>input.  A series thing that is a.... battery or..capacitor with uneven 
>length plates on the schematic.  With B.C. written by it.  One on each 
>input and both are doing the same. If I short one side of the device away 
>from the grid, little difference. If I short the side on the control grid 
>then it totally eliminates the hum noise.
>
> Now...these things...have like a wire going into a porcelain 'tube' on 
> both ends.  And a piece those fit into that looks like a funnel shaped 
> washer with some rubber insert on one side... and there is a wire crimped 
> around the porcelain on both sides so it's just a U shape basically with 
> the open ends of the U crimped around both porcelain pieces if you can 
> picture that.
>
> What were those supposed to be?  Anyone?  Never seen a part quite like 
> that.
>
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