Boss ME-50 issue

[stevenrb718]

Looks like the 4552 rabbit hole was a red herring. Pulled one from a good BF-3 and got the same results. Seems like the distortion is coming from the audio serial data input and output lines, which go directly into the 144 pin microcontroller. Not sure if those are pre-programmed or even available for purchase. I'm pretty sure I have the 3.3V at the MC, but I'll check for broken traces anyway. I assume the audio serial data line is the post-effect line?

[stevenrb718]

Those inputs all go directly into the 144 pin IC. If the 4552 is not actually at fault and it is caused by clock, etc, then I'd assume that IC would be the culprit, and I doubt that's replaceable. I'll have to mess around a bit more later on.

[g1]

Yes, the clock and a few other inputs must be good. MCLK, LRCK, BCLK, SDTI. Have a look at all of them with the scope, sometimes you will see something real obvious, like very low level or distorted waveform.
Datasheet for AK4552 attached.

[stevenrb718]

Have you checked the voltages to the socket with the chip out vs in? With a signal checker is the audio clean up to the socket with chip in /out?

nosaj

Voltages on pins 4, 5, & 6 are all about 3.3V with or without the IC in place. Both channels of the audio coming into the IC are fine.

I managed to find a few more Boss pedals I have that don't work in various ways, which all have a 4552. I pulled the IC from one of them and dropped it in the ME-50... still no change. I can't imagine I came across 3 nonfunctional 4552s, but maybe? It might be a dumb question, but could something else be forcing the 4552 to create a distorted signal, like the clock?

[g1]

You might have to look for some other junk unit that uses that same chip, like in that other pedal you have. Sometimes you can pick up working units pretty cheap, but not sure how much time & effort you want to put into this.
Some boss & roland stuff, some Line 6 stuff. google "AK4552" (in quotes) along with any of those brand names to find model #'s.

[nosaj]

All good, that's why I was hoping to verify my 2 chips are bad, as sourcing replacements is pretty difficult.

Have you checked the voltages to the socket with the chip out vs in? With a signal checker is the audio clean up to the socket with chip in /out?

nosaj

[nosaj]

This is all i could find
The product sellpoints well leave a lot to be desired.
Is this and old chip I can check at the parts warehouse i go to next time.

[stevenrb718]

All good, that's why I was hoping to verify my 2 chips are bad, as sourcing replacements is pretty difficult.

[nosaj]

My apologies
nosaj

[stevenrb718]

Is this not one? It was in the search
nosaj

No, that's a 4452 not 4552, plus that's a 32 pin square casing whereas the one I'm looking for is 14 pin rectangular casing.

[nosaj]

Is this not one? It was in the search
nosaj

[stevenrb718]

Google is your friend.
nosaj

I appreciate witty retorts as much as anybody, but that or any other search doesn't even produce a single AK4552.

[nosaj]

Google is your friend.
nosaj

[stevenrb718]

Any idea where I could source the AK4552? Would be rather surprising that 2 separate Boss units would have a faulty AK4552 in the same manner, but still possible.

[Jazz P Bass]

The AK4552 is pretty much plug & play.
Proper clock & power supply and it should work.