[Johnson] ranger fuse

[David C. Hallam]

I think that Johnson relied on the assumption that good hams always securely
grounded their equipment.  The manual states that the equipment should be
grounded with a wire that is not a multiple of a 1/4 wave length on any
frequency of operation.  "GOOD LUCK"  I have just acquired a Viking Invader
2000.  The chassis of the HV power supply is the neutral side of the 115V
supply for things like fans, LV transformers, etc.  As long as you operate
from 240V with a neutral that is grounded, I suppose this is safe.    The
exciter portion of the Invader is not wired that way.  But if you do operate
from 115V, you had better be sure the outlet is wired properly.  I am
considering rewiring the HV PS and run 115V neutral wires isolated from the
chassis.

David
KC2JD

-----Original Message-----
From: johnson-bounces at mailman.qth.net
[mailto:johnson-bounces at mailman.qth.net]On Behalf Of K6JEK
Sent: Thursday, February 16, 2006 3:48 PM
To: johnson at mailman.qth.net
Subject: Re: [Johnson] ranger fuse



I've been taught to never put a fuse in the neutral line.  If there is
a fault that puts the AC hot line somewhere that it shouldn't be and
the neutral fuse blows, the danger still exists possibly right at your
fingertips.   There have been many discussions of this topic on this
forum including a nice post in defense of the Johnson design which
maybe made sense at the time given the common wiring of the time.   But
it doesn't make sense now especially for a 50 year old  radio in which
failing components are likely.

On the AC bypass cap issue --  replacing them is a great idea.  We need
to make sure they are capacitors designed for the purpose not the
ordinary vanilla disc ceramics we have in our junk boxes.  For across
the linethey should be a type Y capacitor.  These are readily available
from Mouser, Newark, Digikey.   Here's a link the Vishay/Sprague
website that describes theirs:
http://www.vishay.com/docs/23092/aclinecp.pdf

They seem to have changed part numbers since I bought my supply of
X1/Y2's which in addition to being the safe part for the job have the
bonus of being a beautiful electric blue.   What could be more
appropriate?

Jon, K6JEK

On Feb 16, 2006, at 11:04 AM, SBJohnston at aol.com wrote:

>
>> it's worth noting that the plug fuse values are asymetrical
>> eg... they are NOT the same value..and arent supposed to be. see
>> manual
>
> That's why I used two when I modded my Ranger...
>
> Steve  WD8DAS
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