Something maybe is loading the rail.
Yes, that was my initial thought as well.
I desoldered the two main supply smoothing caps to see if that would bring up the rail voltage - it did not.
The rest is all SMD and I lack the tools to work that effectively (I only have a soldering iron).
(I do have some experience soldering SMD but not so much desoldering -without destroying the part)
The master clock is not super high frequency (12MHz) and not being full swing should not matter that much as long as it reaches the specs of the MCU and DSP clock input.
Yeah - but now it sort of oscillates in a +/-500 mV range somewhere around the 2V level... So no way any logic IC is gonna see that as a clock.
Did you look into the data sheet of that DSP?
No. I figured it did not matter much as long as there is no clock and the reset stays active...
The master reset not being released can have several causes. Best test might be to see if the FLASH (U4) is being addressed. Easiest with a logic analyzer (cheap 8 bit 24MHz one will do). That one can contain the code for the DSP, but it might also be that the MCU uses it for its own code to. Depends on what type it is of course, but did not see it in the schematic.
I interpreted it as the MCU being fed the board clock and having startup code that releases the master_reset (that's how I would implement it)...
I'm pretty sure nothing is accessing the FLASH (U4) when there is no clock and reset is active - but I haven't measured it. It's all SMD so I'd have to solder on some wires to be able to measure that.
Do you have some good pictures of the main board?
No - I couldn't find any online - so I will make some (when I get home).
What do you hope to learn from the photo's?
BTW: I also desoldered the power amp IC (TDA2050) that was getting warm without any load. I figured I could tackle that problem later (I have some in stock).