[TenTec] blow-up number 5

[Larry DiGioia]

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 at 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

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