[Fourlanders] W4ZST 6m amp

[Bob Lear]

Well, you guys know I don't work very fast and I wasn't really in a 
hurry but the 6m amp has been repaired and is once again fully operational.

The exciting contest episode was one of the DC blocking caps blew, 
causing a short and the fuse to blow.  Burnt smell in the shack.

After consulting with Ray and Dick, I was pleased to hear that the tubes 
or other components probably weren't damaged in the incident. Ray looked 
over the original Commander layout and suggested that I put some thermal 
mass on the DC blocking caps to help dissipate the heat.  You may 
remember that the first problem I had with this amp was excess heat at 
the DC blocking caps which caused a melt-down of the support 
insulators.  Those were replaced with ceramic insulators and are still 
fine.  Ray gave me some 1/8" thick copper that I cut into a teardrop 
shape for the bottom plate and a triangular shape for the top plate of 
the DC blocking caps.  He also suggested that I put 3 blocking caps 
instead of the original two, thus the teardrop and triangle.  He also 
suggested a heavier strap from the top of the caps to the tank coil.  
The original mounting for the caps was just thin 1/4" wide silver plated 
copper strap.  I made the parts, silver plated them, installed, burned 
in the tubes with no high voltage for a day or so and finally got to 
testing today.

TA_DA!!  Working fine, full output, no undesirable smells, loud noises 
from arcs or anything.  Putting out full power so the amp is back in 
business for use here and contesting.
This amp was designed pre-WSJT and I probably shouldn't have had it as 
high out as I did for the contest when Jim operated all night FSK-441 
and made 18 Q's.  I could improve the cooling but I think about 500 out 
for FSK-441 should really be plenty and I don't think we'll have any 
more problems.

If anyone wants to see pictures, let me know and I can send you some.

Heading out next week to the SVHFS conference.  Hope to see some of you 
there.

73, Bob