Help w/Amp 80m Anomaly?

Martin Ellis jmellis at
Thu Jan 16 02:03:51 EST 1997

Brian Short wrote:
> I recently added a Viking MB-V-A tuner to my station and changed
> my 80m antenna to ladder line fed (160' long, center fed).  I have
> never before tested for any long period this antenna/tuner
> combination with an amplifier.
> Last night I was running about 900-1000w on RTTY.  I was CQ'ing at
> a rather low intermittant rate while working on some other things in
> the shack.  Suddenly, the amp shut down, blowing both 250v 15a fuses.
> I suspect something arced, causing the sudden disruption.
> The SWR to the amp was low over the entire RTTY range.
> Q:  I don't beleive the MB-V-A would arc (settings 14-1-23)?  
> Any suggestions of avoiding future problems?  

Hi Brian,
If you suspect the MB-V-A, I suggest you take off the top cover
and look for discoloration or signs of overheating.

I purchased a used MB-V-A from a sale of surplus equipment from
a previous Greenpeace operation in the Antartic.  The unit had
burned sections of tinned copper braid between the terminals
and the components.  It had been in service with an Alpha 88, into
a variety of non-resonant wire antennas.
After replacing the braid, the unit has operated reliably
at the 400w level for several years.

I would expect that there would be visible signs of any flashover
or overheating if there was a fault in the Viking tuner.

Hope this is of help.

Martin ZL1ANJ

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