[Elecraft] K2 kit building problem

[Gordon LaPoint]

I have checked all the components on the top of the RF board around 
Q6.   I have not removed the heatsink yet to check C122 and the other 
components on the bottom of the board.  Resistance checks show that R48 
and R50 are correct.  The DC voltages on Q6 should show some emitter 
voltage when in TX, but the emitter is at 0VDC.  The 1.8VDC on the base, 
with 12VDC on the collector is trying to tell us something, maybe no 
current flow in the transistor?
   I have not seen or felt any evidence of overheating on any component 
in the radio, at any time.

Gordon - N1MGO

On 3/4/2018 3:10 PM, Don Wilhelm wrote:
> Gordon,
>
> It is doubtful (but possible) that Q6 is bad.  Did it overheat when 
> you powered up? - if it did, you would most likely have seen a wisp of 
> smoke.
>
> How large is the signal at the base of Q6 when you have 800mV P-P on 
> the collector of Q5?
>
> The base voltage on Q6 is higher than normal, it should be around 1.1 
> volts.  I would suggest you check all components in the base circuit 
> of Q6 first.
>
> 73,
> Don W3FPR
>
> On 3/4/2018 2:26 PM, Gordon LaPoint wrote:
>> I'm building a K2 kit and I have a problem.  I'm starting the 
>> Alignment and Test, Part III on page 77-78.   I have no rf out.  I 
>> have followed the rf through the tx chain and have a good signal at 
>> (RF board) Q5 collector (800mv P-P) using a 400Mhz scope.  I have a 
>> signal on Q6 base, but nothing on the collector.  The DC voltage (in 
>> TX) at Q6 is 12.0 Collector, 1.8VDC base and 0 on emitter.  I don't 
>> see anything wrong DC wise, is it likley that Q6 is bad?  What else 
>> should I look for?  With the radio off the R at Q6 emitter to ground 
>> is 1.8ohms, that looks normal, so I don't have any current flow in 
>> Q6, it looks like.