I guess I will try to follow the "Kick start" routine and try to replace a couple of things...
Once voltage is present on U14, switching begins. The clock frequency is determined by C69 and R367 and oscillates at approximately 250-260kHz. 180-degree phased clock signals are provided to U18 for generation of the low and high side gate drive waveforms on pin 7 and 5, respectively. The transistors Q26-Q30 serve to increase the current drive to the IGBTs Q28 and Q31.
Switching commences for the time allotted by the discharge of C196, or approximately 100mS. During this time period the IGBTs transfer energy from the primary bulk storage (C57-C60) and the AC line through the resonant tank (C68 & L3) to the transformer, T1. The energy is magnetically coupled to the secondary of the transformer and hence C43-C48.
Energy is also transferred back to C196 through D26. If the voltage at C196 is
maintained at a point greater then the lower bound for the Vkstart sense comparator, U16B, then the controller circuitry becomes sustained by the converter itself and the kick start cycle is terminated. If for any reason the converter does not sustain the voltage on C196, the kick start cycle will repeat indefinitely approximately every 500-800mS.
I will try the easy to find first (C196, D26). It looks like C196 is the one 'deciding' if the amp finishes the startup sequence... I will measure voltage at C196, if its ok I will replace it.
CCARMINATIMember Since 01 Mar 2007
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04 Sep 2007 - 03:42