Model 
3720A 
4-8 
TEST EQUIPMENT 
4-9 
Table 
4-3 
lists 
the 
test 
equipment required to 
carry  out  the  troubleshooting procedure.  Other 
equipment  with  similar  specifications  may  be 
substituted if desired. 
4-10 
Logic Probe 
4-11 The 
hp 
10525A  Logic  Probe 
is 
used  exten- 
sively in troubleshooting the 3721Al3720A System. 
Power  for  the probe  is  supplied from the 
LOGIC 
PROBE connector on the rear  panel of the 3721A 
Correlator.  This  probe  will  indicate three  logical 
conditions: 
a. 
>2.5V  level 
is 
present. 
When  the  lamp 
is 
glowing brightly, 
a 
steady 
b.  When  the  lamp 
is 
extinguished, 
a 
steady 
<1 .OV  level 
is 
present. 
c.  When  the  lamp  flashes 
or 
glows  dimly, 
a 
pulse  train  is  present,  the  rate  of  flashing being 
an indication of the pulse repetition 
rate. 
Table 
4-3 
Test 
equipment required for System Troubleshooting 
L 
Instrument  Specifications  Recommendation 
Logic Probe 
Indicates TTL logic  levels and pulse trains 
hp 
10525A 
Oscilloscope  50M 
Hz 
bandwidth 
Dual vertical inputs 
Main and delayed timebase 
External triggering facility 
hp 
180Al1801 AI1 82 
with two 
hp 
10004A 
10: 1 Voltage Divider 
Probes 
A 
0 
c 
4-2 
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