E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
A18 CPU Turn–On Test
1-4
6. If DS9 and DS10 are on, proceed to “Checking the A18 CPU Voltages” on page 1- 4.
Checking the A18 CPU Voltages
1. With the external and internal covers removed and the signal generator on its side, turn power on and check to
see if all the power supply LEDs on the A31 Motherboard are on. If any of the power supply LEDs are not on,
refer to “Power Supply Troubleshooting” on page 1- 14 to troubleshoot.
2. If all the power supply LEDs on the motherboard are on, check the A18 CPU and A31 Motherboard connector pins
for the voltages listed in the following table.
3. If any main power supply voltage problems are detected, refer to “Power Supply Troubleshooting” on page 1- 14.
4. If all power supply voltages are good, replace A18 CPU.
Verifying the A18 CPU Turn–On Sequence
Verify the A18 CPU turn–on sequence by observing DS1 to DS8 sequence patterns (See the diagram on page 1- 45 for
LED locations). DS1 to DS8 should match the sequence shown in Table 1- 3. Before verifying the turn–on sequence,
make sure all switches in the upper left–hand corner of the A18 CPU are in the CLOSED (up) position. If the lights
fail to step through the sequence, replace A18 CPU.
No Instrument Control From the Front Panel
Refer to “Front–Panel Display Assembly Troubleshooting” on page 1- 10.
Error Messages
If error messages are reported after the turn–on check is completed, refer to the Error Messages list, located on the
E8257D/67D PSG Signal Generator Documentation Set CD (part number E8251–90351) for details.
Connector Supply Voltage Acceptable Range
P223–2, 22 +5 VA +5.2 ± 0.16 Vdc
P223–3 −15 V_In −15 ± 0.45 Vdc
P223–4 +32 V_In +32 ± 0.96 Vdc
P223–21 +15 V_Standby +14.85 ± 0.6 Vdc
P223–23 +15 V_In +15 ± 0.75 Vdc
P223–37 −7 Vdc −7.0 ± 0.14 Vdc
P223–39 +10 Vdc +10.2 ± 0.2 Vdc
P223–40 +8 Vdc +7.95 ± 0.21 Vdc
Table 1-3 A18 CPU LED Sequence Table
Sequence DS1 DS2 DS3 DS4 DS5 DS6 DS7 DS8
1 XXXXXXXX
2 00X00000
3 XXX00000
4 0XXXXXXX
5 00000000
6 XXXXXXX0
X = LED is on; 0 = LED is off
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