[Elecraft] RE: Problem with KPA100 power output; high current

[Mike Markowski]

Courtney and all,

Courtney Krehbiel wrote:
> ...The real cause of my trouble was dead 1N5711 diodes in the internal SWR
> bridge circuit. The diodes in both the KPA100 and KAT100 were fried...
 > With the RF detector circuit dead and
> measuring no output power, the K2 feedback control process just kept
> trying to drive the unit harder until it reached full bore and
> high-current would ensue...

I had exactly this problem a few weeks ago.  In my case, though, it 
seems a near lightning strike (in winter!) or some other ESD source 
zapped just one of the 5711s in the bridge.  But after that 3 diodes in 
the t/r switch shorted, followed by scorching a few resistors in the PA 
area as well as one in the t/r switch.  Ouch.

With Gary's patient help as well as a few component replenishments from 
Scott (parts at elecraft) I was back in business again.  My lesson learned 
is disconnect the antenna even in winter time.  It still feels good to 
have the rig working again!

73,
Mike ab3ap