Mhz Reference At A15J302 - HP 8560A Service Manual

3.
Check for a 3 Vp-p waveform at A15J302 using an oscilloscope (see Figure 11-3).
4.
Check that the signal at A15J301 is 10 MHz 640 Hz (with TCXO reference) using a
frequency counter. If necessary, perform the appropriate 10 MHz reference adjustment.
5. If there is no problem with INTernal 10 MHz reference operation, check EXTernal 10 MHz
reference operation as follows:
6.
Set the HP 8560A's 10 MHz reference to external by pressing 10 MHz EXT .
7. Connect a 10 MHz, -2 dBm, signal to the rear-panel 10 MHz REF IN/OUT connector.
8.
Check the signals at A15J301, A155302, A15J303, and A15J304 according to the
procedure in steps 2 through 4.
9.
If the signals are correct in EXTernal operation, but not in INTernal operation, the
problem lies in the TCXO, its voltage reference, the TTL level generator, or the A21
OCXO, if Option 003. Check these sections as follows:
On the HP 8560A, press 10 MHz INT .
Check U305 pin 3 for approximately +12 Vdc.
Check for a 10 MHz sine wave, 21 Vp-p, at U302 pin 2 (non-option 003) or J305
(Option 003) using an oscilloscope.
If the signal at U303 pin 5 is correct (see Figure ll-4), but there is a problem with the
10.
signals at A15J301, A15J302, A155303, or A15J304, suspect U303, U304, or U306 in the
10 MHz Distribution Amplifier.
G r a p h I 1 1
1 :
P I N9
1 0 0 0 00
Figure 11-3. 10 MHz Reference at A15J302
v 5 0 0 0 000
RF Section 1 l-15