Posted by
Don Wilhelm-4 on
Feb 18, 2012; 11:08pm
URL: http://elecraft.85.s1.nabble.com/Q7-failure-in-K2-tp7297576p7297788.html
George,
OK, do check D9 for possible damage, or if you have the KAT2 installed,
there are wattmeter dides in that option that may have failed and could
produce the same thing as damaged diodes in the KPA100.
I am not saying the above is your problem, but I am saying, "do check" -
if you have a damaged power measurement component (RF Board D9 or KAT2
wattmeter diodes), you could end up wiith a repeat failure (and that
would not be nice).
Put the new 2N2222s in anyway and then check the base solder pads of Q7
and Q8 before installing Q7 and Q8.
If you do not have good de-soldering equipment - waste the component(s)
by clipping off the leads and remove the leads one at a time. Clean up
the solder pads with solder wick and if the holes are not open, use a
wooden toothpick or a stainless steel needle to open the holes if required.
73,
Don W3FPR
On 2/18/2012 5:39 PM, N9AUP wrote:
> Thanks Don,
>
> I've now pulled the remains of Q7 and also removed Q8. I checked the bias
> and it is at .64 volts and present at both base pads. This is a K2/10, so
> does that rule out the static antenna charge theory? I have a sort of crude
> transistor check which consists of connecting ohm meter - to emitter and +
> to collector (NPN) then touching my finger across base and collector to see
> if resistance decreases. If that means anything in this case, then Q8
> wasn't totally destroyed. Of course, I'll buy the K2PAKIT and install the
> matched pair.
>
> I note that the receiver mode seems to be working just fine. I pulled the
> controller board and turned power on and off to do a relay reset per the
> manual. 40 through 10 meters are open at the moment, the relays are
> clicking and I have reception across the board so the relays/filters must be
> ok.
>
> Can you suggest anything else to check?
>
> 73,
> George
>
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