Identify smt components on circuit board?

[Buk]

Can anyone identify the values/types of the smt components on this board?

Of the 4 top left, the first might be labelled R1( but it looks more like F or P to me); it is possible to tell (or determine) its value?
The next three are labelled C3, C2, C1. Again, values?

The component at the top looks like its labelled B1, but is probably D1. Type?

The big square at the top is a push button; and the round thing bottom is a two wire electret.

My best guess for L/G, E/L, E/R & R/G is Ear Left & Ear Right, Left Ground & Right Ground, which fits in that the earpieces of the headset are connected that end. Corrections invited.

 

[Pommie]

Unless there's numbers on them it's almost impossible to say. I'd trace the circuit and see if that helps. Two of the caps are probably decoupling caps.


Mike.

 

[Buk]

Unless there's numbers on them it's almost impossible to say

No. No numbers. Unless they are lasar etched microscopically. My eyesight close up is pretty good, and I'm using 6x magnification. Nada.

The component I thought might be a diode (top) isn't. It 0Ω on the diode setting both ways; and 0.7Ω both ways on the 20Ω setting?

And the component I thought might be a resistor isn't. It measures 1608Ω one direction and ∞ in the other on the diode setting?

The only information on the caps is the color -- grey, cream and maybe pinky grey left to right.

I'm working on drawing the board and tracing the circuit.

Thanks for the feedback.

 

[rjenkinsgb]

The F item with very low resistance both ways is likely a ferrite bead.
It may have one cap across each earpiece and one across the mic, for more RF suppression?

 

[sagor1]

D1 might still be a diode if it is across something like a speaker. Without a circuit diagram, hard to guess for sure.

 

[Buk]

It may have one cap across each earpiece and one across the mic, for more RF suppression?

Turns out not. Both left and right earphone, and a ground go directly to the other side of the board (through vias highlighted in orange below and straight out to the headset via tracks highlighted ghost blue):

All the components -- the ferrite bead, diode and 3 capacitors are connected to the electret and mic-in. The former in series with the electret and the other 4 in parallel to ground.

When the NO switch is open, the mic-in presents a resistance of 1600Ω to the phone; when pressed, it short-circuits the mic leaving only the 0.7Ω of the ferrit bead; which causes the phone to stop/start playback, stop/start recording or pick-up/hang-up the call depending which app is in control.

The electret receives 2.07V (remaining from the 2.67V the phonve presents on mic-in when open circuit), and must impose its output on that dc signal to be filtered off before the preamp in the phone.

I'm wondering if it would be possible to use those 2V to boost the low frequencies (say < 1500Hz) in a pre-preamp based on a simple rc filter and a j-fet?