Blown R58 relpaced, still no power out, does anyone have any hints?

[stephen Farthing]

Hi Guys,

A few weeks ago I managed to induce a fault into my K2 by transmitting
into no load when testing the top band option. I found that R58, the 180
ohm, half watt resitior at the far end of T4 had been damaged and had a
value of 4 ohms. So I replaced it and reassembled the K2 and I still
have no power out. Before I remove all of the options (ATU, Top Band and
SB) and take it back to basics, which will take time will not have for a
month or so, can anyone suggest other components I might
check.....everything else seemed ok including the PA Transistors......

Also, what is the purpose of R58? Sorry guys but i am just not as clever
as the rest of you, I do software for a living, not electronics...but I
am learning..

Regards,

Steve G0XAR
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[Don Wilhelm-3]

Steve,

With R58 almost a direct short, there is a possibility that the PA
transistors were conducting too hard and caused their untimely demise.  But
it would be best to check the RF voltages first before drawing any drastic
conclusions like that.  There actually could be any number of guesses about
what has failed (everything in the transmit chain) and you need to narrow
the field a bit.

If you do not have one, build the RF Probe shown in the K2 manual
(Troubleshooting appendix, page 9).  Then set the K2 power to 5 watts and
check the RF Voltages at the points indicated on page 14 of the Transmit
Signal Tracing starting with th Xmit Mixer Output - if you are lucky enough
to have a signal greater than that indicated continue along the steps until
you find the stage where the signal drops significantly.  OTOH, if you don't
have enough RF at the Xmit Mixer Output, move back to page 12 second column
and do the steps properly from the beginning.

73,
Don W3FPR

> -----Original Message-----
>
> A few weeks ago I managed to induce a fault into my K2 by transmitting
> into no load when testing the top band option. I found that R58, the 180
> ohm, half watt resitior at the far end of T4 had been damaged and had a
> value of 4 ohms. So I replaced it and reassembled the K2 and I still
> have no power out. Before I remove all of the options (ATU, Top Band and
> SB) and take it back to basics, which will take time will not have for a
> month or so, can anyone suggest other components I might
> check.....everything else seemed ok including the PA Transistors......
>
> Also, what is the purpose of R58? Sorry guys but i am just not as clever
> as the rest of you, I do software for a living, not electronics...but I
> am learning..
>
> Regards,
>
> Steve G0XAR
>

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