[Johnson] Surge protection for Johnson BA's

C Eus catman351 at yahoo.com
Sat Apr 30 00:05:15 EDT 2005


All:
During the final testing of my Viking 2, I noticed a
pronounced "thud" whenever I hit the filament toggle
switch. The "thud" is a manifestation of some large
amount of instantaneous current as it hits the primary
of the power transformer. As AC comes in, your not
guaranteed that the waveform will come in at any zero
point of AC waveform. It could be at a max of 115 VAC
while the primary doesn't have some resistance or
reluctance to stop the incoming current flow. 

I suspect enough of these "thuds" over the lifetime of
a BA will eventually cause it to fail. After hearing
that sickening "thud" for so many times, I decided to
do something about it. I bought some surge protection
devices on ebay. I already used on on my S-40 (in
addition to putting an inline fuse with the cord). In
the case of the Viking 2, I took the jumper from one
of the filter coils to the fuse and in its place in
went one of the surge protection devices. After
installing the device and trying the filament switch
again, no longer were the "thud" sounds of inrush
current were heard! It didn't affect the performance
of the Johnson and needless to say, this is one
transformer that I don't think will see the light of
"P.Dahl's Day". 

For more info on these units, please refer to the
following URL (put out by Canadian Ham Jan Skirrow of
"Boatanchor Dreams" fame).
http://skirrow.org/Boatanchors/TechTalk3.pdf

73 de Cal, N6KYR/8

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