[Elecraft] [K2] No TX Power Out

[David Gilmartin]

Thanks Don,

Problem was with D36 (SMT1B) - used pad 1 and 2 not 2 and 3

RTFM!

73

David EI9EUB



On 20 May 2009, at 17:38, Don Wilhelm wrote:

> David,
>
> When making the Transmit Signal Tracing tests, stop at the *first*  
> place where the RF voltage is substantially *lower* than the  
> expected value.  That stage has inadequate output.  In other words,  
> if the transmit mixer has low output, one can expect low output at  
> all points in the transmit chain beyond the mixer - even though  
> those following stages may be working fine.
>
> Since your first failure stage seemed to be the transmit mixer,  
> check all components shown around U10 on the schematic.  Be certain  
> you are getting enough RF voltage from the VCO to U10 pin 6 (0.5  
> volts minimum).  Additionally, you must have a good signal into U10  
> pin 1 - check the amount of RF voltage at TP2, then both sides of  
> C167 and finally U10 pin 1.  There should be only a small dropoff of  
> the BFO signal as you progress along that path.  Use the level at  
> TP2 for the reference level.
>
> 73,
> Don W3FPR
>
> David Gilmartin wrote:
>> 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
>>
>