TroubleshootingProcedures
6-42 WFM90D and WFM91D Service Manual
Low-VoltagePower Supply
Use the following procedureto check that the low-voltage power supplies are
operating properlybefore proceeding to Fault Symptom Table.
1. Disconnect the AC adapterfrom the WFM90D or WFM91D.
2. Remove any installedbatteries. See Batteries on page 6--28.
3. Remove the top cover.See Top Cover on page 6--5.
4. Connect the AC adapterand turn on the instrument.
5. Check that the low-voltage powersupplies are operating properly, as
indicated by thesupply voltages listed in Table 6--4:
Table6- 4: Low-voltage power supplies
Supply TestPoint Output Ripple
+8V J9, pin 13 40 mV 30 m V
--8 V J9,pin 14 40 mV 30 mV
+5V J9, pin 15 25 mV 60 m V
6. If the low-voltagepower supplies are operating properly, proceed to Fault
Symptom Table.
7. If any of the voltages areout of specification, check the two fuses on the
Bottom board.
CAUTION. Do not use a solderingiron larger than 18 W. Todo so may damage
the circuitboard and the surrounding circuitry.
8. If a fuse is bad, remove the AC adapterand replace the fuse before you retest
the low-voltage powersupplies.
9. If both of the fuses aregood, replacethe Bottom board.
NOTE. Be sureto removeall modules one at a time, to isolate the Bottom board
in a supply is excessivelyloaded.