E8257D/67D, E8663D PSG Signal Generators Service Guide 63
Troubleshooting
Troubleshooting Assembly–Level Problems
b. Disconnect the cable from J1053 A31 Motherboard and connect it
to the DVM.
c. Leave the I/Q modulation on, and make the I offset the active
function.
d. As you rotate the RPG, the voltage displayed on the DVM should
vary from approximately +0.25 Vdc for an offset of 50%, to
approximately −0.25 Vdc for an offset of −50%.
If the signal is bad, check it at J9 of the A13 I/Q Multiplexer.
— If the signal is bad at J9, refer to the A13 I/Q Multiplexer
troubleshooting, on page 55.
— If the signal is good at J9, change the cable.
3. If both the I and Q signals are good, reconnect the cable removed in Step 2
Check the signals at the A8 Output board.
a. At J53–8, repeat the Q offset check in Step 1
— If the signal is good, replace the A8 Output board.
— If the signal is bad, replace the A31 Motherboard.
b. At J53–19, repeat the I offset check in Step 2
— If the signal is good, replace the A8 Output board.
— If the signal is bad, replace the A31 Motherboard.
405 Gain Adjustment Test
— Replace the A8 Output.
406 Prelevel Bypass Test
— Replace the A8 Output.
407 Switched Filters Test
— Replace the A8 Output.
408 ALC Reference DAC Test
— Replace the A8 Output.
409 ALC Modulation Test
— Replace the A8 Output.
410 Burst Mod Driver Test
— Replace the A8 Output.
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