Version: 13. Sepe,mer 2004
16
Now prepare the wires for this group. The 3-Pin Plug, ready with 3 wires is
do make the connection to ST3 on the main board. Twist the 3 wires and
solder one of the SolderPin Plugs to each end. Isolate them partially to
prevent against shorts. ST3/1 MUST go to PIN Y. ST3/2 and ST3/2 can be
interchanged to change tuning direction of the DDS VFO. The other connec-
tions are not used in this section.
Test Section 3
1. Visual inspection (see Section 1)
2. Resistance test (see Section 1)
[ ] rotary encoder at St 3
[ ] connect bridge from pin 18 to pin 47 (see Section 1)
[ ] Apply supply voltage as in Section 1 test.
3. Smoke test (see section 1)
current abt 50 mA
4. Functional test
Method 1:
After turning on, the DDS VFO should oscillate at 4.030 MHz. This is easy to
check with a short wave radio. Make a wire link from isolated wire. The free
ends should be twisted. Leave a small sling at the closed side, and connect
the free ends to ground and antenna input of the receiver respectively. Put
the sling over T2. Turn on power. The receiver should now have a strong
4.030 signal.
Method 2:
Oscilloscope owners could inspect the signal at C13. It should be some 2-3
Vpp.
Method 3:
With an absorbtion frequency meter (or a grid dip meter in absorbtion
position), you should be able to demonstrate the function of the DDS.
Methode 4:
Those who have allready built the speaky counter or own anothe counter
may measure the frequency at C13.The counter should show 4030 +/- 2 kHz
Remove the supply voltage and the bridges, and proceed to the next sec-
tion.
Section 4 IF
The following trimming potentiometer was supposed to be standing. In
practice, this has shown to be difficult to trim. Instead we mount a PT6
lying. The raster is a little too small for this, so the leads of the trimming
potentiometer must be bent carefully. This is a little clumsy to do, but
better clumsy now, than when trimming!
[ ]P6 2,5K PT6 lying E2
IC 11 should be rolled gently, as we did previously.
[ ]IC11 LM386-4 DIL8 E2/3
Now the capacitors
[ ]C111 0,1µF Film RM 5mm D3
[ ]C112 2,2nF 222 E2/3
[ ]C113 22nF 223 E2
[X] C114 10µF/6,3V (SMD) E3/2
Don’t forget to polarize electrolytic capacitors correctly. The
long lead is plus.
[ ]C115 10µF/35V rad. F2/3
[ ]C116 220µF/16V rad. F2
[ ]C117 220µF/16V rad. F2
[X] C118 47nF SMD 0805 E2
[ ]C125 10nF 103 D2
[ ]R79 22K E2/3
[ ]R80 1M D3
[ ]R83 100k D2
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