Re: 40M QCX problem uponpower up


Alan G4ZFQ
 

Han's voltage table T1 pins 5, 6, 7 & 8 2.36 volts
your check T1 pins 5,6,7,8  all 0.30
Assembly Manual Section 5.5 explains circuit.
R1 & R2 are both 10K Ohms configured as as a voltage divider.
You have approx 5v on the top end of R2?
There SHOULD be approx half voltage junction R1 & R2
0 Ohm continuity from the other end of R1 to 0V rail connection
how does the voltage divider check out?
next possibles, T1 secondary winding continuity 1 & 2 or IC4 internal s/c pin 7/9 to 0V (unlikely)?
Alan,

The T1 connections are switched to the IC5 inputs, IC5A inputs are low. IC5B are nearer the expected.
Do you think a shorted C43 or C44 might cause this?

73 Alan G4ZFQ


I measured voltages using the internal DVM.  I did not measure the LCD because it works fine.   Many of these are way off - I hope a better tech than me sees a pattern here!  Sorry for the long post.
Here they are:
+ supply terminal   12.12
Clk0 test pin  1.70
Clk1 test pin  1.70    both approximate
Left side C2  3.46
Right side D2  5.02
T1 pins 1,2,3,4   all zero
T1 pins 5,6,7,8  all 0.30
Top side of C43  0.26
Top side of C44  0.24
                  C45  0.41
                  C46  0.51
IC5 pin 1  11.00
            2   0.35
             3  0.33
            4   0
            5  0.51
            6  0.51
            7  4.00
            8  11.79
IC6 pin 1  4.00
            2  4.01
            3  3.29
            4  0
            5  4.15
            6  4.00
            7  4.00
            8  11.79
IC7 pin 1  10.19
            2   9.70
            3  8.19
            4  0
            5  7.89
            6  9.80
            7  10.86
            8  11.79
IC8 pin 1  7.36
             2 7.36
             3  0.87
             4  0
             5  1.20
             6  7.38
             7  7.35
             8  11.79
IC9 pin 1  4.86
            2  4.86
            3  0.65
            4  0
            5  1.10
            6  7.34
            7  7.34
            8  11.89
IC10 pin 1  5.92
               2 5.92
               3  5.92
               4  0
               5  4.27
               6  3.86
               7  5.77
               8  11.47

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