[CQ-Contest] Amazing PJ2T Corrosion Photo

Keith Morehouse kjm at probeelectronics.com
Sat Feb 14 14:47:24 EST 2009

K1TTT wrote:

 > So not only has it been exposed, as long as the
 > fan was running it probably had nice humid salty
 > air being forced to flow around it.

I recall several MLA2500's we used at various Carib multi-op's in the 
80's and 90's that could not be turned off after a few days of running 
because of salt build-up on the ceramic part of the tubes directly in 
the airflow of the fan.  They ran along just fine as long as they stayed 
on.  Once you turned them off, restarting them would cause HV to arc 
from the plate structure to the ground ring at the base - easily a half 
inch of ceramic.  The arc would destroy the plate voltage over-current 
protection resistor and require a disassembly of the PA.  One would also 
have to pull the tubes and wipe them down with a damp rag.  Once the 
failure mode was figured out, we simply left the PA's on for 2 weeks 
straight :)

Those MLA's were in accelerated stages of chassis corrosion after 2 trips.

Jay W9RM
(VP5KMX, VP2V/K9GL, J87J,  ect)

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