[Elecraft] K2 - Q7 and Q8 failure

[Don Wilhelm]

Ken,

That is normally the result of unmatched transistors for Q7 and Q8, but 
Elecraft has been supplying matched transistors for the last 3 years.
I suspect that you have some incorrect components in the Q7/Q8 base circuit.

After checking everything in the Q7/Q8 base circuit, check the PA bias 
voltage before installing the new Q7/Q8.
Do a TUNE and monitor the voltage at the base solder pads for Q7 and 
Q8,  the voltage should be between 0,60 and 0.64 volts.  If it is not 
replace Q11 and Q13 and then recheck.

Check all the components in the Q7 and Q8 base circuit for proper values 
and good soldering.

73,
Don W3FPR

On 12/28/2015 8:52 PM, K and K Stuber wrote:
> While operating my K2 (SN 7581) on CW I heard a loud pop! I traced it to
> blown Q7 and Q8. They are physically blown apart. The K2 was operating
> normally before this happened. Everything else seems to be OK except for no
> power output. The driver seems to be working; I can key the radio and hear
> it in another RX. The K2's RX is working normally. Any thoughts as to why
> this happened would be appreciated.
>