[Elecraft] Low power with K2/100

[Peter]

Hi all,

It turns out that pin 17 on U2 has an undefined voltage.
When NOT selected that band (40/30M) it must be 12V. I measure 7V.
The input for this switch is pin 2 at U2  Here I measure 0V (=good) and 
goes HI (5V) when selected
So U1 is working well

Will heading tomorrow for a new U2

Peter



Don Wilhelm schreef:
> Peter,
>
> The fastest way to determine if you have a problem with the Low Pass 
> Filter in the KPA100 is to check it with an antenna analyzer.
>
> Disconnect the small coax to the K2 RF board and terminate it with a 
> 50 ohm (51 is OK) resistor.  Power only the base K2 (the ribbon cable 
> must be connected). Then switch the K2 to the band of interest and 
> connect the antenna analyzer to the SO239 antenna jack and sweep the 
> band.  If the SWR in the band is about 1:2, then the Low Pass filter 
> for that band is OK.  If something is wrong, you will see a much 
> higher SWR.
>
> An analysis of the sweep results along with a look at the schematic of 
> the relay contacts should reveal whether you have a bad relay.
>
> 73,
> Don W3FPR
>
> Peter wrote:
>> Hi
>>
>> After a few years of good service,I  have a problem with the K2 output.
>> I  have the K2 with K2/100.
>>
>> The barefoot K2 put full power out on all bands via the bnc connector
>> When I connect the K2/100 with PA off with the menu there will be low 
>> power on the ant connector on the higher bands (15/12/10 meter).
>> Since 10/12/15 are combined, I suspect the bandpass filter
>>
>> I tested from TP2 and ANT. out and see NO interruption  when change 
>> to an other band.
>> All C's, L's  and solders look good.
>>
>> So I guess there will a bad relais thats stay ON when I go to 10/12/15M
>>
>> The relais in the BPF  are  N.O. when not selected, right?
>> If so, I can measure between de N.O. and COMMON to see if the 
>> connection goes away
>>
>> Futher more, there is 12V at U2 (pin 14 18,17,16,15,14) when the 
>> relais in NOT selected. If selected the needs pin good down to 0V, 
>> right?
>>
>> Any other thing to look at?
>>
>> Peter
>> PC2A
>
>
>