Vco Band Select - Watkins-Johnson Company WJ-8718-19/FE Instruction Manual

MAINTENANCE
WJ-8718-19/FE HF RECEIVER
Table 4-19. VCO Band Select Code
TUNED FREQUENCY
BAND
E3
SELECT OUTPUT (Vdc)
E2 El
1
i
0.00 - 3.99 MHz
+ 15 +15 +15
i
4.00 - 7.99 MHz
+ 15
+15 - 12
8.00 - 11.99 MHz
+ 15 - 12 + 15
12.00 - 15.99 MHz
+ 15 - 12 - 12
16.00 - 19.99 MHz
- 12
+15 +15
20.00 - 23.99 MHz
- 12 +15 - 12
24.00 - 27.99 MHz
- 12 - 12 +15
28.00 - 29.99 MHz
- 12
- 12 - 12
r
10. Divider Section -
nn nnnnn \auv r,p o i c t
With a
T f\ inrvii
tuned frequency of
-
the following frequencies in Table 4-20 should be
found at the corresponding IC pins using a Digital
Counter.
Table 4-20. 1st LO Frequency Chart
IC PIN FREQUENCY
IC PIN FREQUENCY
Ul 7
17 MHz
U9
5
1.68 MHz
Ul
9 3.4 MHz
U9
9 80 kHz
Ul 10
40 kHz
U9 2
40 kHz
U2
12
3.4 MHz
U10 3
840 kHz
U3
7 40 kHz
U10
7
200 kHz
U3
9 40 kHz
Ull
6 40 kHz
U5
3
40 kHz Ull
7
40 kHz
U8 7
200 kHz U12
5 40 kHz
U24
1 40 kHz
U12 9
40 kHz
4-40
12. Phase Detector U5 - Check for 40 kHz signal at input
pin 3 of U5. If signal is not present, troubleshoot Time
Base Circuits. Check for 40 kHz signal at pin 1 of U5.
If not present, troubleshoot 1st LO counter circuits.
With a tuned frequency of 00.00000 MHz, the Phase
Detector output at U7-6 should be approximately -8
Vdc. If not good, check U5, U6, U7, CR1 and CR2.