Specifications

1. Pull out the Buffer module and attach a clip lead onto
the front end of R16.
2. Reinsert Buffer Module
3. Route the clip lead through the air holes in the inner
door so the door can be closed.
4. Connect a scope probe to the clip lead, and turn on only
the Low voltage. There should be a 4 to 4.5Vp-p RF
signal present.
5. If not, then refer to the overall wiring diagram and
Frequency Synthesizer Troubleshooting to trace the
loss of signal.
6. If the RF is present, then check the DC supply voltage
to the Buffer.
b. Determining that the DC Supply voltage is present on the
module during Step Start sequence can be done by placing
the probe (610-1131-000) or equivalent X10 probe on the
Drain of Q1. During step start you should see a +20-
45VDC signal.
1. If this is not present refer to Section VI, Troubleshoot-
ing, the Overall wiring diagram, and the Driver Com-
biner schematic to trace the missing voltage.
c. If the supply voltage is present, verify that an RF drive
waveform is present at the output of Buffer A during the
Step Start sequence.
1. Then look at Buffer B output and verify the presence
ofthesamewaveform.
2. If both outputs have an RF signal refer to the Driver
Combiner Schematic to locate a missing trace or bad
connector.
3. If both outputs do not have an RF signal, check TP1
for a 15Vp-p RF signal during step start and replace
U1 if missing. (RF Drive to the input of U1 was verified
in a previous step).
888-2339-002 C-9
WARNING: Disconnect primary power prior to servicing.