Rebranded Raidmax RX-735AP Powers Up even without plugged in mobo

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  • felix
    Member
    • May 2008
    • 34

    #1

    Rebranded Raidmax RX-735AP Powers Up even without plugged in mobo

    Hello all,

    The above PSU fell into my hands after the owner replaced it with a new one (better brand).

    The fan had failed and the PSU did not power on before i got it.
    The fan rotor had a large crack and the axis was stuck in the bearing.

    However when i got it the leds of the fan were lit while plugged. The leds were powered from a separate 5v supply on the PCB.

    I recapped all the output caps using KZH series.

    Got a new fan and the psu was ready to test.

    I plugged it in a test system i have and everything was ok.

    I even ran a combined stress test (Furmark for the NV 450GTS and Prime for the 4 core Phenom II of the system) for 5-6 hours.

    I thought it was ok, as it passed the stress test. But 2-3 secs after i powered off the system, the PSU was trying to start again followed by some chirping sounds and the leds of the fan pulsing.

    I removed the 24pin and 8pin and 6pinGPU cables from the motherboard and when i swithed the PSU switch on again it started the same thing ! Without any cables plugged in the motherboard.

    I also had some light smell but no visible marks of something burnt.

    After that i tried again and the PSU started normally again. Then after system shut down, the same thing again.

    Only "visible" sign of some temperature increase is the cables of a thermistor on the heatsink of the output transistors.


    Supervisor IC is Sitronix ST9S313A-DAG, if it is any clue to anyone.

    The internals are shown in this review --> here.

    I also uploaded some photos of the thermistor ( it had a metal holder bolted on the heatsink) and supervisor IC area


    Any thoughts are welcome.

    Thank you in advance !
    Attached Files
    Last edited by felix; 05-03-2017, 03:05 PM. Reason: Photos upload

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