k2 PA blown....

[F5UL]

Hi, all Once again I have to come here to ask for help. The last thunderstorm took its toll, and I just changed the 2 x 2sc1969. The results are very disturbing !

On 40, 30, 20 and 17 m the signal look normal wheb in full power (10+ w), but as soon as I start reducing the power level and depending on band, the signal start to be mushy, finaly ending in burst of a few millisecond (seen on the scope). On 160and 80 m the bursts are present whatever power level is selected. Same on higher bands 15 to 10 m

I took photos of scope screen if it will help anybody able to help me solve this problem.

Thanks in advance, and reply direct if necessary!

F5UL/Bob
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[Don Wilhelm-3]

Bob,

A lightning surge sufficient to blow out the PA transistors is likely to
have also blown the 1N5711 diode in the output power measurement circuit.
D9 on the RF Board or if you have the KAT2, D1 and D2 on that assembly, or
if you have the KAT100 the diodes in that are also D1 and D2.

If these diodes are damaged, the K2 will not be able to properly control the
power output and will likely output its full power capability.

I do not understand your observation of 'mushy' bursts, but in the case of a
lightning surge I would arbitrarily replace the diodes mentioned above and
then see what the result may be.

73,
Don W3FPR

> -----Original Message-----
>
> Hi, all Once again I have to come here to ask for help. The last
> thunderstorm took its toll, and I just changed the 2 x 2sc1969.
> The results are very disturbing !
>
> On 40, 30, 20 and 17 m the signal look normal wheb in full power
> (10+ w), but as soon as I start reducing the power level and
> depending on band, the signal start to be mushy, finaly ending in
> burst of a few millisecond (seen on the scope). On 160and 80 m
> the bursts are present whatever power level is selected. Same on
> higher bands 15 to 10 m
>
> I took photos of scope screen if it will help anybody able to
> help me solve this problem.
>
> Thanks in advance, and reply direct if necessary!
>
> F5UL/Bob
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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> Elecraft web page: http://www.elecraft.com
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