Conway,
The DC Voltages are OK - even for Q24. Recall that I asked you to
measure while in CAL FCTR. That places a voltage on the VALC signal
line. It normally is used for power control and is developed on the
Control Board at Q8.
So the problem is that the BFO is not oscillating. First steps are to
check soldering of the BFO components X3, X4, C174, C173, D38 and D39.
Examine L33 carefully to be certain the very fine wires are soldered to
the leads of the 1/8 watt resistor.
Measure the resistance between the solder pads that L33 and its mounting
resistor are soldered to - if the resistance is in the megohm range,
then L33 either has an unsoldered lead or has a broken wire.
Check the orientation of D38 and D37.
The other components in the BFO circuit help control the frequency, but
your problem is that it is not oscillating.
Jumpers are not the problem, but you should have installed W1 through W6
during the Assembly Part II
73,
Don W3FPR
Conway Yee wrote:
>> Does your counter probe report a frequency reading when plugged into
>> TP1? If so, the probe is working, if not, then your problem is with
>> either the probe itself or the Q9 and Q10 circuits on the Control Board.
>>
>
> The frequency probe is fine.
>
> TP3 shows 12099.11
> when I switch to TP2, I read zero.
>
>
>> Turn your manual to Appendix E page 11 and do the 4 test steps indicated
>> at the top of the 1st column. Then compare the DC voltages during CAL
>> FCTR at the leads of Q24 and U11. If that does not reveal the problem
>> for you, tell us what those measurements are an we may be able to help.
>>
>
> >From Appendix E, the BFO fails to oscillate.
> BFO Output : Vrms = 0.001
> BFO buffer output : Vrms = 0.008
>
> [measurments done with Fluke 77, AC voltage]
>
> U11 DC voltages appear nominal
> pin 1 : 1.403 manual 1.4
> 2 : 1.403 1.4
> 3 : 0 0
> 4 : 4.75 5.0
> 5 : 4.76 5.0
> 6 : 5.86 6.1
> 7 : 5.44 5.6
> 8 : 5.92 6.1
>
> Q24 DC voltages are abnormal
> S : 0 manual 0.0
> G : 0 1.2
> D : 0 1.3
>
> Looking at the circuit diagram, nothing is soldered to the other side of
> R98, V_{alc}. Could this be the problem?
>
> I am unable to find where in the circuit diagram V_{alc} is hiding.
>
> On the circuit board, it appears that jumpers are supposed to be there. I
> am also unable to find in the construction instructions I was supposed
> to (or not) place what appears to be jumpers in the area.
>
> tnx.
> Conway Yee, N2JWQ
>
>
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