Hi Larry,
Sorry you're having so many problems. It looks to be a real
mystery but there must be an answer. BTW you CAN get an
electrostatic charge on the antenna that will take out diodes
easily. Those diodes you're talking about have a fairly low PIV,
I think around 100V, so it wouldn't take much to take them out. I
had just such a problem with my Delta 580 15 or so years ago. One
day I would start operating on 75M and no ALC control. The diodes
in the power meter would be open and these are also the power
control circuit. It took me a while to figure it out but what was
happening was this. I had a B&W coax switch with all the antennas
connected. Far CW was the park position and nothing connected to
it. One click CCW was the coax from the remote Heathkit switch
with the beams. two clicks CCW was the 20M vertical, three clicks
CCW was the 40M dipole and four clicks CCW was the 75M dipole.
Now this problem got so bad that I put sockets in for the diodes
so I could change them quickly. To make a long story short I
found frequently when I switched to the 40M dipole or passed it
to go to the 75M dipole the diodes blew. I then begin to
experiment with the 40M dipole and connected a spark gap of a few
mils width to the coax. Watching it about every 30 seconds or so
if the wind was blowing it would discharge. So the dipole was
building up a charge and with it connected to the coax switch
which had no grounding except the shield when the coax switch
went to the 40M position it had to discharge through the rig
which took out the diodes. I took the switch apart and put a 500K
resistor from each coax center lead to ground and have never had
a problem since. Maybe you have a similar problem though it seems
yours happens while operating.
73 Jim K4CGY
--- Larry DiGioia <listacct@longwire.com> wrote:
> Some of you will recall my tale of the repeated failure of (it
> turns
> out) diodes and other components in the driver stage of my
> Omni-6 Plus.
> I have had it back to Ten-Tec 4 times for the same problem.
>
> To be specific, this was (per the last service ticket) "D-2, 3,
> 4, 5, 6,
> 7, 8, 9 on the low-pass filter, R-10, 11, and D-7, 8, 9 on the
> bandpass
> filter."
>
>
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