[Elecraft] K2/KPA100: External Amplifier Keying Test (PA Key) Problem

[JF1KGX]

Don,

I have checked what you advised.
But envrything looks fine.
I don't believe that Q9 itself is something wromg.

Thank you,
Hideki
JF1KGX

----- Original Message ----- 
From: "Don Wilhelm" <w3fpr at embarqmail.com>
To: "JF1KGX" <jf1kgx at jarl.com>
Cc: <elecraft at mailman.qth.net>
Sent: Wednesday, July 29, 2009 6:47 AM
Subject: Re: [Elecraft] K2/KPA100: External Amplifier Keying Test (PA Key) 
Problem


> Hideki,
>
> With power off, check the resistance from the source of Q9 to ground.  If 
> you can check from the lead of Q9 rather than the solder connection.  If 
> it is not zero ohms, you have a soldering problem there.
>
> If the source of Q9 is well grounded, next check the voltage at the Q9 
> gate during TUNE - it should be in the 3 to 5 volt range. - if lower than 
> that, check the soldering and value of R1 and the soldering at U1 pin 16 
> (pin 16 of U1 should be very near 5 volts during TUNE).
>
> If all is good with those checks, Q9 itself is the prime suspect (but I 
> have never hear of one being a problem).
>
> 73,
> Don W3FPR
>
> JF1KGX wrote:
>> Somebody has asked the same before. But nothing has been replied.
>> Now I have the same problem.
>>
>> Page 49 of the KPA100 instructions calls for testing the resistance 
>> between
>> ground and the tab of Q9 on the KPA100 board (or center conductor of the 
>> PA KEY
>> output jack, J7).
>>
>> According to the instructions, the resistance should drop to less than 3 
>> ohms
>> when the K2 is put into TUNE mode.  Mine only drops to about 270 ohms. 
>> The
>> troubleshooting in the KPA100 manual doesn't even include any information 
>> for
>> what to do if the resistance doesn't drop to less than 3 ohms.
>>
>> So far everything else seems to be working correctly with the KPA100.
>> My serial number is 06617.
>>
>> Please advise me.
>>
>> Thanks
>>
>> Hideki
>> JF1KGX
>>
>>
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>