Season's greetings to all,
Well I was thinking that my building experience would be uneventful, after
successful completion and testing of the basic K2, but after the
installation of the SSB adapter a problem showed up:
First, after installing the SSB board everything seemed fine and the Rx
filters sounded fine, also did the carrier balance alignment as per the
manual (using the K2 S-meter reading) which was fine too.
BUT when I connected a Yaesu mic (and another one acted the same) after
properly configuring the connector at the front panel board), no Tx output.
The K2 goes into Tx mode, Rx muted and the power consumption goes from 240mA
in Rx to 440-460mA in Tx but there is absolutely no power out when speaking
on the mic at any preset power level. Activating the TUNE option does
produce normal RF out just as before.
Did inspect the SSB, Control and Front panel boards for soldering problems
and found none.
Finally did the voltage testing and it seems that most of my measured
voltages on the SSB board are slightly lower than expected, for example
U1pin9 on TX has 1.08V instead of 2.3V required, with other measurements
being significantly lower:
Rx (required) Tx (required)
U1-21 5.6 (5.8) 0.1(0.02)
U1-22 0.13(0.2) 0.0(0.0)
U1-25 0.0(0.0) 0.65(0.8-1.2)
U1-28 5.6(5.6) 5.47(2.4) !!!!!
U2-5 0.47(0.6) 0.6(0.6)
U2-8 5.98(6.0) 3.06(5.4) !!!
U3-4 1.4(1.7) 1.7(1.7)
U3-5 0.2(0.4) 0.4(0.4)
U3-6 0.0(0.0) 0.6(0.8-1.2)
The above are the most abnormal values, from which I have put exclamation
marks at the larger discrepancy values, the first one being the AUX-BUS
U1-28 pin of the microcontroller. I tend to think that there lies the sourse
of the problem, but have not been able to proceed any further with my
diagnostics...
Saw some similar postings at the reflector which have been traced to bad
solder joints or not removal of the required jumpers from the RF board
before installation, but unfortunately, that does not seem to be the problem
in my case...
Anyone has any ideas? I do have a 40Mhz oscilloscope available, but it
seems that this problem might be related to microcontroler communication
rather than AF signal loss.
73,
Marinos, ki4gin.
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