Focal FPS 4160 weak sound on one channel

[Maxikill97]

Hi there guys,


Got a Focal FPS 4160 laying here, where I'm struggling on for a couple months now.
The amplifier is making a lower amplitude but clear sound at CH2 on the speaker output.


I checked the output of the filter circuit and the sine wave amplitude is excactly the same which is going to the input of the driver board. So, both driver boards (CH1 and CH2) has the same input sine wave amplitude.
The output of the driver board from CH2 has a weaker sine wave amplitude.


I checked and compared all resistors from the driver boards, measured the transistors and diodes, but I could not find a difference in readings between both driver boards.


Does anybody had the same problem? Or somebody knows how to fix this?
Attached are the schematics of CH2 from the driver board input to the speaker output.

Q11, R1, R14, R20, R13 reads OK

 

[Perry Babin]

Do you have the same signal level on both sides of E1 on both boards?

Is the level on E1 the same in both channels?

E2 can also affect the gain level of the power amplifier stage.

 

[Maxikill97]

Yes, on both sides of E1 the amplitude is the same.


The readings of E1 are ok, measured with an capacitance meter.

 

[Perry Babin]

Did you check E2?

 

[Maxikill97]

E2 seemed to be the problem.
The cap should read 22uf, but it readed 26pf (it wasn't shorted)

Replaced it, now it works great.


Thanks Perry ��