PT80 - Function of 47uF across pins 2/3 of PT2399

[bdevlin]

I have a testy unit.  Looking at the components I see my 47uF cap looks black on top.  Haven't tested it yet but I am hoping someone can tell me what purpose it serves.

[bioroids]

It is supposed to be the bypass capacitor for the 2.5v reference voltage I understand (to avoid AC fluctuations on the reference voltage). I don't think the IC can work fine with that cap damaged.

Luck!

Miguel

[dschwartz]

just for learning....

that means that this capacitor sends to ground any AC component ind the 2.5 supply?

[igor12]

"this capacitor sends to ground any AC component ind the 2.5 supply"

Yes, I believe so, although the primary source of AC noise is the clock on board the PT2399.

[bioroids]

And also that is the reference used in the internal opamps, so the audio is bypassed by this capacitor too (just like the capacitor in the 4.5v voltage reference on the standard opamp circuit).

Luck!

Miguel