Troubleshooting Procedures
6–32 WFM 90 and WFM 91 Service Manual
Battery-Fault Analysis
Use this procedure to troubleshoot battery or battery charging problems when the
instrument functions properly when powered by the AC adapter. If there are no
battery problems or if the instrument does not function properly with the AC
adapter, go to Low-Voltage Power Supply on page 6–35.
Use the following procedure to determine if the battery charger circuit is
operating properly:
NOTE. The battery-charging circuit in the WFM90 (SN B011362 and below) and
the WFM 91 (SN B010470 and below) will not charge a completely discharged
battery. The battery must have at least +4 V charge across the battery connector
before the charging circuit will operate.
1. Remove the AC adapter from the WFM 90 or WFM 91 Handheld Wave-
form, Vector, Picture, and Audio Monitor.
2. Remove the battery cover and any installed batteries from the instrument.
See Batteries on page 6–21.
3. Use three jumper wires to connect two 30 W, 3 W resistors and an external
+12 VDC power supply to the battery connector pins. See Figure 6–15.
Battery connector
+
–
+12V
Test resistor #2
Test resistor #1
External power supply
Jumper wires (3)
Figure 6–15: Testing the battery charging circuit – WFM90 SN B011362 and below;
WFM 91 SN B010470 and below
WFM 90 SN B011362
and Below;
WFM 91 SN B010470
and Below