Version: 13. September 2004
25
Now the easy part, the pins, and you complete this section.
[ ] pin 12
A5
[ ] pin 14
B5
[ ] pin 15
B5
[ ] pin 22
B3
[ ] pin 19
C4
Test Section 7
1. Visual inspection
(see Section 1)
2. Resistance test
(see Section 1)
Now install R57, you remember, this resistor helps optimizing the intermo-
dulation characteristic. My way to optimize is as follows:
I do not install the resistor directly into its holes, but I install to pieces of
wire instead as standoffs. Now I solder a 220R resistor to both of the
standoffs. This trick makes it easier to change the value of the resistor if
needed. To make it possible to measure the current, we need all power
supplies now.
[ ] pin 29 to +10 Volt (see Section 5)
[ ] pin 19 to 10V
[ ] pin 15 to 10 V
[ ] Bridge pin 47 to pin 18
[ ] Bridge pin 20 to ground
3. Smoke test
(see Section 1)
[ ] Apply power supply as in Section 1
Total current should be abt 100 mA
No we use Mr. OHMs law to calculate the quiescent current:
measure the voltage across R 57. If Mr. Ohms law is correct and we get 10
mA, you should see U=RxI = 220R x 0,01A = 2.2V. If you measure much
more ore less, the current is not ok and you must change the Resistor
(assuming Mr.Ohms Law is ok :-) Try to get the current to 10mA +/- 2mA by
changing the resistor.
If this is ok, you can do the functional Test.
4. Functional test
You should hear noise in the head phones. The
simple test with the finger on the input, as with
the BFO, won’t work this time, as the crystal filter
only will allow 8 MHz to be received (Actually
rather 7.999 MHz, as the centre frequency of the
Cohn filter depending on band width is a little
lower than the individual crystals).
At this place, we need a signal generator. A simple, but very usefull tool is
the little Xtal controlled testoscillator / Xtal Tester you can order from
QRPproject. If you have a variable transmitter, you can use that. Connect
it to a dummy load at low power, and tune it to 7.999 MHz. A link wire
connected to point Input 7.999 MHz should give a beat tone in the head
phone, if the transmitter frequency is changed slightly.
Remove all bridges after the test, and proceed to Section 8.
Input
7,999
Mhz
