[Elecraft] K2 BFO level at TP2 question

[Don Sandstrom]

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