HP 8340A Service Manual page 213

(6) IS HLEY HIGH?
HLEY (High Lock Enabl� Yig oscillator) must be HIGH for the YO
Loop to lock. If HLEY is LOW or intermittent, then troubleshoot
the A59 Digital Interface board. If not, then proceed to question
7 .
IS M/N OUTPUT FREQUENCY AND POWER OK?
(7)
Check for the proper M/N signal frequency and power at the output
of A33J2. The correct frequency can be found by pressing
on the front panel that will display the following.
[Ml]
M N
M/N FREQUENCY
# #
The correct M/N signal power is 0 dBm +3 dB. If no signal is
present or if the power and/or frequency is incorrect,
troubleshoot the M/N Loop. If the M/N signal is correct, then
proceed to question 8.
(8) IS 20-30 OUTPUT FREQUENCY AND POWER OK?
Check for the proper 20-30 signal frequency and power at the
output of A36J2. The correct frequency can be found by pressing
SHIFT Ml on the front panel
power is 0 dBm +3 dB. If no power is present or if the power
and/or frequency is incorrect, then troubleshoot the 20-30 Loop.
If the signal is correct,
(9) IS THE YO FREQUENCY CHANGE PROPORTIONAL TO YO TUNE?
Record the actual YO frequency. Then disconnect YO TUNE and FM
COIL DRIVE, cables A49Jl and A49J2. Place a 50 Ohm load on the YO
TUNE cable, A49J2.
remainder of the troubleshooting.)
Note the YO frequency now and compare it with th� value recorded
before the cables were removed. It should have changed
approximately 20 MHz. The YO frequency sensitivity to YO TUNE is
approximately -3.0 MHz/Volt. If the frequency does not change or
else changes an amount much greater than 20 MHz,
problem on the A55 YO Driver
If the frequency change is proportional to the YO TUNE voltage,
then proceed to question 10.
(10) IS THE OPEN-LOOP YO FREQUENCY ACCURACY +5 MHz AT 2.300 AND
6.999 GHz?
Model 8340A
(MHz)
(see question
then proceed to question 9.
(These cables will remain disconnected for the
(Block
Scans by HB9HCA and HB9FSX
Service
�
20-30 FREQUENCY
above). The correct
7
this indicates a
E).
[SHIFT]
(MHz)
then
8-291