On Wed, 3 Feb 2010, Don Wilhelm wrote:
> So the problem is that the BFO is not oscillating.
Searching some more, I am no longer certain that this is the case, I have
been using a Fluke 77 for AC voltage measurements. Checking the spec
sheet, it appears thaat AC voltages are measured from 100mV to 750V with a
frequency range from 45Hz to 1KHz. Certainly the BFO voltages are too low
and the frequency too high to register.
Testing this theory, I place my Fluke 77 to TP3 which is KNOWN to have
12099Hz, I read 0V. This MAY explain my zero measurements on TP2 and pin
6 of U11.
Trying the frequency probe on pin 6, I see 4913.11Hz!!!! This is also seen
on pin 7 (as expected). I also see the same on both sides of D37
(although slightly higher frequency 4913.38Hz. Nothing is seen on TP2.
and possibly on C168 (unstable number much smaller than 4913, mostly in
the 2000 range). In summary, assuming that the signal is from the
crystal, I see it up to the gate of J310 but not on the source.
Does this mean that I have managed to fry Q24?
I note that V_{alc} is zero. Could I have missed something that is
supposed to be hooked up to the other side of R98? I still can't find a
jumper in the instructions that is supposed to be soldered to the tracing
extending from the other side of R98 toward the control board.
Also, what test equipment am I supposed to purchase that is able to
measure voltages in the MHz range? I can break out my oscilloscope but
this seems overkill for the job. Is there a handheld multimeter that can
handle HF frequency measurements?
tnx.
Conway Yee, N2JWQ
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