[Elecraft] k2: KPA 100 capacitor Specs. etc.

[jferg977 at aol.com]

Ron,
your experience is similar to mine. Your snaps are identical to the ones i heard before I did what I describe next.  There is a lot of history to the ESD problems on Arcadian
?and yes, in  some conditions, you could hear the zaps all over the boat.
The precautions are much more recent.  I wound a 240 torroid to produce 1 milliHenry inductance and shunted the antenna lead-in to "ground/salt water"
where it came into the cabin .  No apparent ESD problems since then.

No more fried 1N5711's.  I feel, though, that the failing capacitors may be residual from some of the more exciting failures associated with no output power control
due to SWR sniffing circuits having been fried by a Zap.  I ususally feel that if a component doesn't fail when it is abused, it won't fail later either, but????
Radio is working fb right now.  

I'm thinking about doing what Bill recommends and I discussed with Don, upping the caps to 100 volt size.  But if problem continues, even this might not be enough.  It may also be good to see if I'm getting ESD into the radio via some other 
route than the obvious.  This would be a real aggravation if I didn't enjoy working on the K2 so much.

NO, I don't either have masochistic tendencies.

73   john

Is it possible you're setup is arcing inside the relay? 

You're probably very familiar with shipboard environments and have taken
precautions so forgive me if I'm stating the obvious to you. I keep
remembering how often I've been knocked on my a$$ simply by carelessly
grabbing onto a disconnected antenna wire. Even the common 22 ft fiberglass
marine "whips" have been known to produce arcs. One time I walked into a
darkened radio room and saw a tiny flash and heard a "snap" before I turned
the lights on. I waited and a few seconds later it happened again. It was
coming from a disconnected PL259 on the end of a coax leading to one of
those whips that "Sparky" had left disconnected. Static was collecting fast
enough to cause regular flash-over from the center pin to the shell. 

So what I have in mind is that if your antenna doesn't have a good enough
d-c ground return circuit for extreme conditions perhaps enough charge is
developing to arc over inside the ATU and, in this case, perhaps it has
found a path from the relay contacts to the coil then to a ground, taking
out the bypass cap with it. 

As you know, once an arc occurs the carbon path it creates will encourage
further discharges to follow the same circuit (and through the same parts)

Ron AC7AC




 


 




>>
>>
>>