Ok. The unit does have sound but no volume control up or down. The joystick up/down/left/right functions do work. The parking cable is grounded.

 

1. I replaced the encoder with a salvaged encoder and still have same problem. Unlikely (but possible) that both encoders have the same problem.

2. I rechecked all ribbon cables and wiring, etc. All were properly seated and there were no visible cracks in the cables.

3. There are no external devices connected to the unit. The unit is not set to ipod or ext or anything like that.

4. I checked all the diodes on the encoder PCB and all seemed good.

5. Reset button didn't help.

 

Are there settings that could do this?

Any ideas?

Using a multimeter I was able to ring out the encoder and It does function as expected.

 

The joystick functions up/down/left/right of the encoder work as expected.

In the schematic, the only components in line with the encoder and the uPC are two surface mount transistors. These check out good, but could still be faulty.

I also found a surface mount fuse that was open (not really part of the volume control circuit) but replacing it had no effect on volume control.

I am still at it.