94 E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Assembly–Level Problems
1607 Paren <–> SH4 Comm
— Replace the A14 Baseband Generator
1608 VCO Tune Test
— If the +32 V, ±15V, –5.2 V2, and + 5.2V supply voltages are good on the
motherboard, use an oscilloscope to check the 10 MHz signal on the A31
Motherboard at P161 pins 26 and 91. The signal should have a period of
100 ns with an amplitude greater than 0.4 Vpp.
— If the 10 MHz signal is good, replace the A14 Baseband Generator.
— If the 10 MHz signal is bad, check it at the A7 Reference.
• If the 10 MHz signal is bad at the A7 Reference, refer to A7
Reference troubleshooting.
• If the 10 MHz signal is good at the A7 Reference, replace the
A31 Motherboard.
— If the +32 V, ± 15 V, and +5.2 V supply voltages are bad on the motherboard,
check the origin of the supply.
— If the supply voltage is good at the origin, replace the A31
Motherboard.
— If the supply voltage is bad at the origin, troubleshoot the A19 Power
Supply.
— If the –5.2 V2 supply voltage is bad on the motherboard, check the –7 V
supply voltage at the A19 Power Supply.
— If the –7 V supply voltage is good at the A19 Power Supply, replace
the A31 Motherboard.
— If the –7 V supply voltage is bad at the A19 Power Supply,
troubleshoot the A19 Power supply.
1609 IQ DAC Output
— Replace the A14 Baseband Generator
1610 PLL Test
— Replace the A14 Baseband Generator
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