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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