[Elecraft] [K2] No TX Power Out

[David Gilmartin]

Hi,

This is my second K2 build

Just got to Alignment and Test Part III and can't get RF out.



Receiver tests OK

Supply is 13.8V

8V regulator gives 7.59V

5V regulator gives 4.99V

AGC threshold is 3.6V (highest voltage I can get) - same as first K2  
built.



No measurable power out - display says 0.1 W in Tune mode

Indicated current:

220mA - RX
520mA - TX

Indicated Voltage:

13.4V - RX
13.2V - TX

4.97V on VPWR at pin 2 of U8 with key down

RF detector components and soldering checked OK




Basic Voltage Checks:

D6 anode goes to 240mV on TX

D7 anode goes to  7.49V on TX




I am having difficulty with the Mixer, Buffer, Band Pass Filter, T-R  
Switch and subsequent tests.

I have built the RF probe and it works OK. All of the measurements for  
the tests above show a trace of voltage on switching to TX which then  
disappears.




Problem in the T-R Switch or am I missing something obvious?

Any help appreciated.

David
EI9EUB