Need Experts Help!!

Hello, I'm having trouble repairing a kenwood DTS Amp model: KRF-7775D. I have the service manual but still could not find any faulty components. Problem with this is that it works on it's own, seems it has a mind of it's own, so I seviced and replaced the memory backup caps near the main u-com and it fixed the "Mind" problem. Now it's doing exactly what I want it except no Audio output. checked everything, output stage, protection, muting etc. no luck. But if I remove the DSP assy ( which has the DAC's, sub u-com and the DSP chip) I can get audio from the dvd 6 channel direct input. sounds great. but if I insert the card the damn thing goes mute. so I checked the card ( voltages and the resets) found that the DSP power (3.3V) is missing. the funny thing is this voltage is present at power on and dies when the protection relay switches on and mute deactivates. The DSP is powered down and is not activated in any sound modes or input modes, so my guess is with the DSP power down the DAC's are not workin, and with the card removed the u-com bypasses this stage. I replaced the sub u-com chip but nothing happened. further checking revealed that after the sub u-com recieves the master reset from the main u-com, it powers down the 3.3V AVR. So after few seconds the after power on the 3.3V dies. I donno why, cud not think of anything, but I did find the master clk from main u-com to the sub u-com is at 3 volts. But to my knowledge it should be 3.3V. Cause the clk goes via level shifter 5V-3.3V IC. After a long struggle I think I have pinpointed the problem. Re-checked every thing, the reset voltages and the supply voltages, audio switching. and these are the results I can get Audio from the speakers only at DVD 6 ch input, and only if I disconnect the sub mute which is activated from the sub u-com. so I think when the sub u-com powers down it mutes the amps, but the main mutes are not activated which means the main u-com is working. After a hard struggle found the Master data out port is always grounded(this is the MDT to the sub u-com) where else the master clk, sub reset and master reset and the volume control data is found the respective ports of the main u-com via to sub u-com. So if U have any idea, or do u believe this is true, pls I need an answer on to which could be the fault. Is the MDT port of the main u-com shorted to ground or is the software malfunctioning ( later is just what I think the Ic is doing). How can I be sure why this pin does not produce any data at swictch on or when I switch the DSP functions are switched. I can get supply variations at the clk, rst and sub rst ports at switch on. but blank on the MDT out. Rifaa