Wayne N2WK
A common fault which develops in the 402BA is a puncture hole through the
plastic cap which sits on the driven element centre and insulates from the
boom. A carbon track develops and will break down at a certain power level.
The cause is usually (1) running too much power off frequency from its
design frequency or (2) a lightning strike (or near by surge) which creates
enough voltage between the driven element and the boom to puncture the cap
which is about 3 mm thick.
Solution: purchase and replace the plastic cap.
Interestingly, the same caps are used on the TH3/TH6/TH7 series, but the
beta match which grounds the elements to the boom, usually protects the
caps.
Good luck
Cheers
Peter Forbes VK3QI
|