490 Chapter9
Controller Section
Frequency Counter (8560EC)
1. Disconnect W22 from A2J9.
2. If a 10 MHz, TTL-level signal is not present at the end of W22,
continue with step 3. If a 10 MHz signal is present at W22, proceed
as follows:
a. Reconnect W22 to A2J9.
b. Set the spectrum analyzer to the following settings:
Span ................................................................... ZeroSpan
Sweep time ................................................................ 20ms
c. Monitor the signal at A2J2 pin 21. This is an output of the
frequency counter, HBUCKET PULSE.
d. If HBUCKET PULSE is stuck high, troubleshoot the frequency
counter.
3. Check for a 10 MHz signal at A15J302. If the signal is not present at
A15J302, the A15 RF assembly is probably defective.
Table 9-2 Gate Times
Counter Res Gate Time*
(U15 pin 20
low state)
A2TP16 A2TP15
10 Hz 200 ms 2 MHz 4.18 kHz
100 Hz 20 ms 2 MHz 418 Hz
1 kHz 2 ms 2 MHz 41.8 Hz
10 kHz 2 ms 2 MHz 41.8 Hz
100 kHz 2 ms 2 MHz 41.8 Hz
1 MHz 2 ms 2 MHz 41.8 Hz
* U15 pin 10 = (FREQ COUNT input × Gate Time)/256
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