[Johnson] Viking Invader need some ideas

[Normiehall@aol.com]

In a message dated 02/18/2003 10:16:23 PM Pacific Standard Time, 
bbc39668@yahoo.com writes:


> Upon inspection of the rig I am noticing that Johnson
> used a shielded type cable in what at quick glance
> appears to be the speech amp section as I can see it
> is wired to the Audio Pot. This shielded cable seems
> to have broken down and has become "crispy" and falls
> apart easily and I am quite concerned about it giving
> me problems.
> Can anyone out there familiar with this rig or that
> shielded cable offer any advice on where to obtain
> this type of wire or if unshielded wire can be
> substituted?
> 

Hi Joe,

I don't have a Viking Invader so can't advise about its peculiarities.
However, regarding the shielded audio wiring, this was a common practice to 
avoid AC hum pickup in the low level audio circuits.  This was done on long 
leads like those that run from the actual tube circuits to front panel 
controls.  Often, the wiring is just regular stranded hookup wire that has 
been threaded into a woven braid shield.  If that is the case with the 
invader, you may be able to remove the old wire and rethread some new hookup 
wire.  It doesn't have to be large gauge since the wire only carries very low 
level signals.  Another approach which I have used quite often in the past 
twenty years is RG-174 minicoax cable for shielded audio cable.  This is 
small, neat and has an outer jacket to protect the shield from shorting out 
to any circuits on the way to the pot on the front panel.  While it is 
intended for 50 Ohm RF circuits, it is quite satisfactory for low level, high 
impedance audio circuits and anything in between.

Good luck & 73,

Norm Hall, W6JOD


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