A friend of mind ask a favor to look at this Denon midi hifi system. The unit was not able to power-up ( power cut-off after 2-3 seconds ).

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Fully disassemble the whole unit for diagnosis.

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Focus on the power module, checked the output voltage on all the regulators, check the cooling fan control system.

Found one of the 5V Regulator with crack solders on all the 3 terminals.

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This system is also protected by a cooling fan control circuit, it actually monitor the duty cycle of the fan and cut off the power during malfunction. In this case I found the fan was not spinning consistently and tend to slow down. Sometimes it doesn't even kick start during power up. Managed to replace with a new one.

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Successfully repaired, the power system is now stable and doesn't cut-off intermittently. Short clips attached. 

Nice job and good pics