Maybe a K2 guru might know what is going on with S/N 4450 I
am building. On trying the BFO Test procedure on man page
62, I don't get enough signal at TP2 to register on the
frequency counter. Everything checked out fine up to this point.
Using the RF probe, I measure about 0.6 Vrms at U11, pin 6,
and with the scope see about 2 Vp-p there. At the gate of
Q24, there is 0.3 Vp-p. But I can barely see any signal
coming out the Q24 source at TP2 only a couple of millivolts
at best.
Putting the frequency counter probe on U11, pin 6 gives a
good reading, and the low and high frequencies and range are
nicely within spec.
Checking further, I think no signal at TP2 is not surprising
as there is no bias applied to Q24 through R98 from V ALC.
Tracing back to the control board this is due to no input to
the ALC circuit at V PWR, which comes from the DAC U8, pin2.
Voltage there is 0.0. I couldn't find any short to ground at
this point.
Any ideas as to why there would be no voltage biasing Q24?
According to the K2 manual, I Appendix E, page 11, I should
see 0.025-0.070 Vrms at TP2, but see negligible signal
instead. I tried another transistor at Q24 with the same result.
I tried a processor reset just in case something else had
upset the state of V PWR, but result was the same.
Thanks for any insight someone might provide.
73 - Don, W7VXS
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