Scodiddly
Well-known member
I just recently bought one of those Mackie "Onyx Satellite" things pretty cheap second hand, but it turns out to have a nasty high frequency whine when phantom power is switched on.
So it's a fun challenge! I'm still wrangling with tech support over this, but I was able to find some schematics too, and I'm figuring that I'll probably end up doing some soldering rather than getting it fixed by Mackie, assuming the latter is even an option since they seem to be abandoning this product.
Here's the phantom power DC-DC oscillator:
According to the notes, last revision was "R5 change from 10k to 301, phantom Fsw from 6k to 160k". I did a little poking around for sample 555 timer circuits and didn't see one that looked like the above, so I'm wondering if the resistor change from 10k to 301 ohms makes sense for that frequency change. Obviously taking it out of the audible range seems like a no-brainer, especially if a single resistor can do it.
Plausible?
I haven't cracked the case open yet to see which revision I have.
So it's a fun challenge! I'm still wrangling with tech support over this, but I was able to find some schematics too, and I'm figuring that I'll probably end up doing some soldering rather than getting it fixed by Mackie, assuming the latter is even an option since they seem to be abandoning this product.
Here's the phantom power DC-DC oscillator:
According to the notes, last revision was "R5 change from 10k to 301, phantom Fsw from 6k to 160k". I did a little poking around for sample 555 timer circuits and didn't see one that looked like the above, so I'm wondering if the resistor change from 10k to 301 ohms makes sense for that frequency change. Obviously taking it out of the audible range seems like a no-brainer, especially if a single resistor can do it.
Plausible?
I haven't cracked the case open yet to see which revision I have.