Boss ME-50 not powering up

[stevenrb718]

I have a Boss ME-50 that isn't powering up. I have 9V at various places, but I believe I'm missing the 3.3V line. The schematic I found online doesn't zoom in clear enough for me to see where the 3.3V rail comes from or what in the line could be killing it. Anybody had a similar issue, or at least a better schematic?

"Our community is saddened by the recent loss of long-time member and very good friend, Enzo.
'Education is what you're left with after you have forgotten what you have learned'"

That's terrible. He helped me many times in the past, and reading his comments on other issues were always insightful and informative. RIP

[The Dude]

Here's a good copy of the full service manual: The 3.3V comes from IC14 according to the manual's block diagram.

boss_me_50_sm.pdf

[stevenrb718]

Thank you for that. Well that's unfortunate. I got 9V going into IC14, but nothing coming out. I replaced the chip, and now have 5 and change coming directly out of it, but maybe 250mv after D6. Pulled the diode and is testing fine, so something is obviously killing my 3.3V line somewhere in the rail. I injected 3.3V into that point, but the board only pulls about 0.02A if I remember right, most of the time. Occasionally it might pull slightly more and lock a few LEDs on. The line doesn't seem to be shorting to ground anywhere, and nothing is getting hot. Guess now that I can see the schematic, I'll go around the 3.3V rail and pull components.

[The Dude]

What voltage do you have on pin 6 of the IC? Also, check to see that L3 is not open.

[stevenrb718]

The coil has continuity, and pin 6 is 570mv.

[stevenrb718]

Well I have since found C125 popped with the can totally missing, and Q9 with a gouge down to metal. Not sure if these add directly to my issue, or if it's a compounded issue...now I fear fried ICs. Waiting for replacement transistors to continue.

[stevenrb718]

Replaced C125 and Q9, still no startup. Down the rabbit hole I go.

[stevenrb718]

So I finally got some parts in to swap and now have proper voltage throughout. The board powers up, but the audio is a distorted mess. I traced the audio line into the AK4552 IC fine, but the L and R audio out of the IC was this distorted mess. I swapped the IC with one from a Boss pedal (that I suspect might also be bad, but thought maybe not in the same manner) and the signal is still distorted. I'm getting the proper 3.3V into the IC from a regulator, and proper paths go to ground. I'm not sure if the AK4552 is even at fault, but they're seemingly difficult to come by at a lower price. I don't believe I can just substitute with a different IC, but again not sure. Is there any other way I could verify the IC as faulty?