E8257D/67D, E8663D PSG Signal Generators Service Guide 23TroubleshootingA18 CPU Turn–On Test4. Inspect the pins on the A31 Motherboard connector. If the pins look goodreplace the A18 CPU.5. If either of the voltages are missing, refer to “Power SupplyTroubleshooting” on page 37.6. If DS9 and DS10 are on, proceed to “Checking the A18 CPU Voltages” onpage 23.Checking the A18 CPU Voltages1. With the external and internal covers removed and the signal generator onits side, turn power on and check to see if all the power supply LEDs on theA31 Motherboard are on. If any of the power supply LEDs are not on, referto “Power Supply Troubleshooting” on page 37 to troubleshoot.2. If all the power supply LEDs on the motherboard are on, check the A18CPU and A31 Motherboard connector pins for the voltages listed in thefollowing table.3. If any main power supply voltage problems are detected, refer to “PowerSupply Troubleshooting” on page 37.4. If all power supply voltages are good, replace A18 CPU.Verifying the A18 CPU Turn–On SequenceVerify the A18 CPU turn–on sequence by observing DS1 to DS8 sequencepatterns (See the diagram on page 76 for LED locations). DS1 to DS8 shouldmatch the sequence shown in Table 1-3. Before verifying the turn–onsequence, make sure all switches in the upper left–hand corner of the A18 CPUare in the CLOSED (up) position. If the lights fail to step through the sequence,replace A18 CPU.Connector Supply Vol tage Acceptable RangeP223–2, 22 +5 VA +5.2 ± 0.16 VdcP223–3 −15 V_In −15 ± 0.45 VdcP223–4 +32 V_In +32 ± 0.96 VdcP223–21 +15 V_Standby +14.85 ± 0.6 VdcP223–23 +15 V_In +15 ± 0.75 VdcP223–37 −7 Vdc −7.0 ± 0.14 VdcP223–39 +10 Vdc +10.2 ± 0.2 VdcP223–40 +8 Vdc +7.95 ± 0.21 Vdc
