CE 4000 Service Manual
Maintenance 4-6
130485-1 Rev. B
©2002 Crown Audio, Inc.
4.4.3 Troubleshooting Power Supply, PFC PWA and
Full Bridge DC to DC Converter
1. Using an oscilloscope check power supply clocks
at TP-253 and TP-12, as shown in Figure 4.12. All
measurements are with respect to SMPS reference.
Figure 4.12 Power Supply Clock
2. Place jumper between J28 and J29 to simulate
front panel switch on.
3. Remove/ bypass boost inductor L1 and using an
external power supply apply 4VDC at J23.
4. Using an oscilloscope check PFC gate switching
at TP-5 with respect to TP-2, as shown in Figure
4.13.
Figure 4.13 PFC Gate Switching at 4VDC
Figure 4.14 PFC Gate Switching at 60VDC
5. Using an external power supply apply 60VDC
to J23 and verify that the frequency changes, as
shown in Figure 4.14.
6. Using an oscilloscope check gate switching of the
Full Bridge DC to DC Converter, as shown in Figure
4.15. Verify the phase shift at startup. Probe at TP-27,
TP-29, TP-30 and TP-31. All measurements are with
respect to SMPS reference.
Figure 4.15 Full-Bridge DC to DC Converter
Gate Switching
4.4.4 Identifying Symptoms
Why was the amplifi er brought in for repair? Can you
get it to malfunction again? Some problems can be
intermittent and diffi cult to fi nd.
Once you have identifi ed and verifi ed the symptoms,
you can look for helpful information in Section 4.4.5 as
to where the cause of the problem is located.
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