258 of 282 M-SV-001-EN Rev. G
8. Verify the bearings and bearing sensors. Refer to "4.31.3 Bearing Sensor Verification" on page
229.
9. Re-apply the compressor power.
10. Test the Backplane voltages at the HV+, +17HV, +24V, +15, +5, and -15 VDC test points.
• If all voltages are within (+/- 10%) the PWM is draining energy.
• If any of these voltages are not within (+/- 10%) another component is draining energy.
5.5.2.4 Determining if Inverter is Draining Energy
1. Remove the Service Side Cover.
2. Test the Backplane voltage at the +24V test point.
3. While measuring the +24V test point voltage, give the compressor the demand to run.
• If the +24V reading drops below 22VDC at the moment the demand to drive is given, the
Inverter is faulty.
• If the +24V reading does not change at the moment the demand to drive is given, another
component is draining energy.
5.5.2.5 Determining if Compressor I/O Board is Draining Energy
Refer to "4.4.2.1 Determining if the Compressor Interface Module is Draining Energy" on page 65.
5.5.2.6 Determining the Cause of Blown Soft Start Fuses (Closed-Top Soft Start Only)
1. Verify the Soft Start fuses
2. An open F1 fuse may indicate a problem with the DC-DC.
• Using the DC Bus Test Harness, verify the DC-DC Converter high voltage input. Refer to
"4.25.2.1 Input Voltage Verification" on page 201.
• Verify the DC-DC Converter. Refer to "4.25.2 DC-DC Converter Verification" on page 201.
• Verify the PWM. Refer to "4.29.3 PWM Verification" on page 220.
• Verify the bearings. Refer to "4.30.3 Bearing Verification" on page 223.
3. An open F2 fuse may indicate a problem with the DC-DC Converter.
• Verify the DC-DC Converter 15VAC input resistance (Potted DC-DC only). Refer to "4.25.2.3
Input Resistance Measurement" on page 202.
4. An open F3 or F6 fuse may indicate a problem with the Soft Start Circuit Board.
• Verify the SCRs and SCR gates. Refer to "4.19.2.1 Diodes Verification - Two Hole Mount" on
page 135.
• Replace the fuse.
• Reapply power.
• If the fuse fails again, replace the Soft Start.
5. An open F4 or F5 fuse may indicate a problem with the Soft Start Transformers, Soft Start
Circuit Board, or DC-DC Converter.
• Verify the DC-DC 15VAC input resistance (Potted DC-DC only). Refer to Refer to "4.25.2.3
Input Resistance Measurement" on page 202.
• Verify the SCRs and SCR gates. Refer to "4.19.2.1 Diodes Verification - Two Hole Mount" on
page 135.
• If no faulty component is identified, replace the fuse and reapply power.
• If the fuse fails again, replace the Soft Start. Refer to "4.15.3 Soft Start Removal and
Installation" on page 112.
NOTE
Refer to "4.15.2.2 Verifying Soft Start Fuses" on page 110 for details on verifying Soft Start fuses.
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