Audio Systems: Infinity repair, infinity model, audio circuits

Question
Hi,

I live in Brazil.
I have a car MMC Eclipse 1995 with a car sound Infinity model E026.

I am technical electronic and I am trying to repair the car audio E026.
My car audio is not having volume control, I think the problem would be in the volume potentiometer..

I disassembled the car audio and I removed the volume button, but it is not a potentiometer I discovered that it is an encoder. . .
Is a potentiometer or is an encoder?

Please, here in Brazil I don't know nobody that knows say me with testing this encoder. Can you explain to me as I test this encoder using an oscilloscope?

I would like a lot of repairing my car original audio.
Thank you very much for your attention.

Best Regards,
Evandro Pinheiro

Answer
Here is a sort of generic IC controller for volume control in audio circuits that may be interesting for you to study:

http://www.datasheetcatalog.org/datasheet/PrincetonTechnologyCorporation/mXvsvzz...

Here are some other simple digital volume controllers.  They may be similar to the one used in your EO26:

http://www.aaroncake.net/circuits/volume.asp

In your radio unit you must check the analog input to the volume control circuit to prove that the controller is getting a good analog audio signal. If so and the output is not correct you must check soldering and wiring and finally replace the ic unit.