Mark,

When you have the problem, look at the voltage at P1 pin 6 (that is VRFDET signal)?
If that is high, the MCU will limit power drastically.

Make sure Q1 is properly oriented.  If that does not help, try a mod to the KSB2 - reduce R9 to 1.5k and cut the trace between P1 pin 6 and the base of Q1 (on the top of the board) and insert a 1k resistor across the trace cut.
That will calm ALC problems with the KSB2, and otherwise will do no harm.

73,
Don W3FPR

On 5/8/2021 1:44 PM, M Bak wrote:
Today I finished the KSB2 adapter and installed it into my K2. It worked
first time but was intermittent. I found the issue as I had omitted to
solder the outer top pins of the twin three pin interconnects. That done
everything seems ok and then........

No Apparent RF output. USB/LSB/CW Pressing TUNE produced a max of 0.8W. VOX
would trip to transmit but the S meter showed no modulation. Coarse carrier
balance adjustment worked but zero S meter readings was very wide (unlike
earlier when it was a fine, narrow adjustment)

All voltages looked slightly low but ball park on the KSB2 board except for
U2 (the DAC) Pin5 which is ALC THR. This was sitting at 5.89v rather than
0.6 on both RX and TX.

I have removed the KSB2 and full CW power output can now be achieved which
is a relief.

I will examine everything under a microscope again but has anyone any
suggestions? I suspect ALC to be the culprit but how to investigate?

Thanks

Mark G4RUR


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