Installation guide

Troubleshooting
Troubleshooting Pulse Modulation and LF Out
1-112
No Pulse Signal from LF Out
To function, the internal pulse generator on the A23 Motherboard requires a 10 MHz reference signal from
the A18 Reference.
1. Assure that all self-tests have passed.
2. If an external 10 MHz reference is connected to the rear panel of the signal generator, remove the
connection.
3. Use an oscilloscope and probe J10-99 of the A23 Motherboard.
There should be a 10 MHz sine wave with an amplitude > 1.2 Vpp.
• If the signal is good at J10-99, use the oscilloscope to probe J10-50.
There should be a square wave with a period of 80 us and an amplitude of approximately 5 Vpp. The
period and pulse width of this signal may be varied using softkeys under the
Pulse menu.
— If the signal is good at J10-50:
a. Turn power off to the signal generator.
b. Remove the A18 Reference.
c. Insert a ribbon cable extender
1
into J53.
d. Ohm between J10-50 and J53-6.
— If the path is good between J10-50 and J53-6,
ohm between the center conductor of the LF Out and J53-13.
— If the path is good between the center conductor of the LF Out and J53-13,
replace the A18 Reference. (Refer to “A18 Reference” on page 2-42.)
— If the path is bad (open) between the center conductor of the LF Out and J53-13,
replace the A19 Daughterboard. (Refer to “A19 Daughterboard” on page 2-44.)
— If the path is bad (open) between J10-50 and J53-6, replace the A19 Daughterboard.
— If the signal is not present at J10-50, replace the A23 Motherboard.
(Refer to “A23 Motherboard” on page 2-52.)
• If the signal is not present at J10-99:
a. Turn power off to the signal generator.
b. Remove the A18 Reference.
c. Insert the ribbon cable extender into J51 on the A19 Daughterboard.
d. Ohm between J10-99 and J51-7 on the A19 Daughterboard.
— If the path is good, replace the A18 Reference.
(Refer to “A18 Reference” on page 2-42.)
— If the path is bad (open), replace the A19 Daughterboard.
(Refer to “A19 Daughterboard” on page 2-44.)
1. The ribbon cable extender needs to be assembled by the user. It consists of two connector plugs
(part number 1252-1010) and approximately eight inches of ribbon cable (part number 8120-2226).
The ribbon cable contains 26 wires; six of these wires need to be stripped off before being connected
to the plugs.