[Elecraft] WSJT K2 Unreliable Output with WSJT

[Kevin Robertson]

Lenny- I have a homebrew K2 built in 2020 with the help of Dave Van Wallaghen who used to service Elecraft rigs. He is an expert on K2’s. I cc’d him on this email. 

I work on FT8 using WSJT-X on my K2 driving a KXPA100 PA with a SignaLINK USB soundcard. Works reliably. Perhaps Dave can help you as he had helped me with my K2. If there is an RF issue in the K2, Dave is the man to solve it. 


73,
Kevin Robertson KD2WCY


> On Nov 29, 2024, at 4:10 PM, pickeringw--- via Elecraft <elecraft at mailman.qth.net> wrote:
> 
> Lenny,
> 
> Do you happen to know how the microphone is jumpered? Is it set for an Elecraft, Yaesu, or Icom? You have to set the jumpers inside of the Rigblaster to be the same as what mic you are set for.
> 
> ________________________________
> From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> on behalf of w2bvh via Elecraft <elecraft at mailman.qth.net>
> Sent: Wednesday, November 27, 2024 3:40 PM
> To: elecraft at mailman.qth.net <elecraft at mailman.qth.net>; don at w3fpr.com <don at w3fpr.com>; Dave Van Wallaghen <dave at elecraft.com>
> Subject: [Elecraft] WSJT K2 Unreliable Output with WSJT
> 
> I have a K2 that I built in 1999. It has KSB2 firmware 1.04, IOC
> firmware 1.09 and main processor firmware 2.04P (no easy way to see what
> version of the KIO2 or KAT2 firmware is without disassembling the module).
> 
> Here is the problem: When running WSJT (FT8) the K2 keys up unreliably
> Sometimes  WSJT keys the K2's PTT and the K2 makes rf and sometimes it
> Keys the K2's PTT but there is no rf output.
> 
> The PTT from the computer (via a usb to rs-232 converter and
> RigBlaster)_ goes into the mic connector. PTT goes to ground every time
> WSJT tries to transmit -- even when the K2 fails to make rf. Similarly,
> there's audio into the K2 mic connector from WSJT every time  WSJT
> transmits-- even when the K2 fails to make rf.  This has me convinced
> that the K2 has a problem (or maybe there is a timing issue).
> 
> I measured the audio on the KSB2 and the the audio makes it out of the
> speech compressor chip on the KSB2 just fine whether or not the K2 is
> correctly making RF or is not making RF.
> 
> I also did some careful measurements on the KSB2 board and found 2 bad
> values when the K2 is not making rf when it should. The measurements I
> made were  on the dual comparator (U4) chip and the DAC (U2) chip.
> 
> 1. First, the "PTT DET" signal out of comparator U4-7 is 0V when the K2
> is making rf and is 6.0V when it is not making RF. The inputs to that
> comaparator ARE THE SAME whether the K2 is making rf or is not! The
> values are 2V offset + low level audio on U4-5 and 0V on U4-6. I thought
> this indicated that the comparator was no good, so I replaced it, but
> have the same result with the new comparator chip. An  VERY ODD and
> unexplainable result!
> 
> 2. Second the "PWR CTRL" signal out of the DAC  (U2-6 ) is 5.5V when the
> K2 is correctly making RF and is 0V when it is not making rf . I don't
> have a logic analyzer so there's no way for me to measure what values
> are being sent to the DAC. And The logic the 16C72 MCU implements when
> feeding the DAC is not explained in the user manual so I can't pursue
> that any further.
> 
>  Spending ~$60 on a new MCU just to see if it's part of the problem or
> not seems like a waste, at least at this point. My MCU is v1.04 and I
> don't even know if the newer firmware would work on this older board.
> Maybe someone is willing to risk lending  me another just to try out.
> (Or maybe a whole board ;-)
> 
> If you have some good ideas, please let me know. This old K2 has made
> many 1000's of q's over the years and I'd really not want to scrap it.
> If you need some of  other measurements , the K2 is still wide open and
> the scope, DMM and computer are sitting there set to go).
> 
> Any advice would be greatly appreciated.
> 
> 73,
> Lenny W2BVH (K2 1520)
> 
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