Might want to look at each side of the line to ground too.
73
Bob, K4TAX
----- Original Message -----
From: "Larry DiGioia" <listacct@longwire.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Sunday, February 12, 2006 7:57 PM
Subject: Re: [TenTec] blow-up number 5
> The PIV is 1000V per Paul. I put a neon tester light across the end of
> the ladderline, I am going to leave it on each one for a few days and
> watch.
>
> James C. Owen, III wrote:
>
>>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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>>
>>
>>
>>
>
>
> --
> Larry N8KU
>
> w w w . l o n g w i r e . c o m
> 100% CW 100% HF
>
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>
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