Reference Receiver Troubleshooting; Figure 8-22. Reference Signal Waveforms - HP 5501B Operating And Service Manual

8-152. Reference Receiver Troubleshooting

a. With power removed from the HP5501B, set the - REF ON jumper on A3 to LO and HTR
OK to HI. Apply power to 55018. Does the READY LED eventually start blinking then
remain on continuously? If no, see HP5501B Trouble Isolation Procedure, paragraph 8-
72 and procedures recommended therein.
b. Are TTL level signals present at A3U16 (Pins 1 and 3) at a frequency between 1.5 and
2.0 MHz? If so the reference receiver may be working properly. If not, trace the signal
path from U17 (Pin 16), through A3Q6, to U16 (Pins 5, 6, and 7 (TP22) and check for the
following:
U17 (Pin 16):
A5J6 Rear Panel
Connector:
0.3 to 0.7 Volt square wave at the Reference frequency of 1.5
to 2.0 MHz.
TP22: TTL level square wave at the REFerence frequency of 1.5 to
2.0 MHz.
Monitor Pins C and D with an oscilloscope. Waveforms should
be similar to those in Figure 8-22.
NOTE
Figure 8-22 oscilloscope settings are as follows:
Time/Division:
Volts/Division:
Coupling:

Figure 8-22. REFerence Signal Waveforms

0.2 microseconds/division
2 Volts/division
DC
HP5501B
Service
8-47