Its been awhile since I have been QRV with my 2m-eme station.
Four independent problems in my transmission line during the winter
kept me off the Moon and then my HVPS acted up. Well it turned out
to be a simple problem but it didn't appear that way. My 4kV dropped
to 2.8kV without a load. I envisioned all kinds of problems but in
the end it was simply a blown HV fuse. It did not blow open but
instead went to 16meg-ohm which was enough to drop the HV with very
low current being drawn by the HV panel meter.
Having no replacement fuse, I decided to remove the HB fuse holder
from the HVPS since changing the fuse required removing the 8877 deck
from the rack to gain access thru the HVPS top plate which is
directly under the amplifier. I will order some more HV fuses from
Nebraska sales ($25/ea.) and make an inline HV fuse box which will be
much quicker access to replace a fuse. Actually, I have only blown
two of these fuses in 8-years of running.
How I blew this one is that the 6-dB attenuator that I was using to
lower drive to my transverter to keep drive below 50w to the 8877
failed in short resulting in over 100w drive to the 8877. Anode
current spiked taking out the HV fuse as it is designed to
do. Probably hit over 2kW output!
A couple other improvements will make recovery from HV events
quicker: I brought the 240vac mains fuses to the front panel of the
HVPS and increased them to 20A. And I added a vernier to the 8877
drive input cap. Looks like I got a finer tune on the input as it is
taking less drive to reach 1200w.
I will be QRV Sunday from about 1400utc to 1700utc (Moonset):
144.116, 1st for CQ and on N0UK logger. Mon> I will be trying to
work 6W/PE1L in Senegal very early in my morning. We only have about
30-min common Moon on Monday but this increases on subsequent days.
73, Ed - KL7UW
"Kits made by KL7UW"
Dubus Mag business: