MAINTENANCE
powermax30 Service Manual 3-17
2
Test 3 — VBUS and voltage balance
Test the power board to ensure that the circuits are balanced.
Step 3
Step 2
Step 4
Caution: Do not use a multimeter with test probes which can cause a short-circuit
between the BUS and the heatsink. Use E-Z Hook® leads instead.
1. Turn OFF the power.
2. Position the multimeter leads to measure the voltage from -VBUS to 375 VDC on the power board. Carefully
connect the E-Z Hooks to the edges of the holes in the power board so that the hook makes contact with the
ring on the back side of the power board.
Turn the power ON after you have connected the E-Z Hooks. The multimeter should read 375 VDC.
If you get a value other than 375 VDC, multiply the reading by 0.00601 to convert it to millivolts. Test pin 21 on
J7. It should have the same value.
3. Turn the power OFF and move the E-Z Hooks to -VBUS and 375 VDC/2. Turn the power ON after you have
connected the multimeter. This value should be 187.5 VDC or one-half of whatever value you found in step 2.
4. Turn the power OFF and move the E-Z Hooks to 375 VDC and 375 VDC/2. Turn the power ON after you have
connected the multimeter. This value should be 187.5 VDC or one-half of whatever value you found in step 2.
5. The values found in steps 3 and 4 should be approximately equal. If they differ by more than 30 V, replace the
power board.
Note: All values can be ±10%.
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