No sound in Toyota Tercel 1992

[Imran]

Hi,

I just installed the JVC KD-SX950 head unit in my car. The system
powers up correctly and does everything except that there is no sound.
The older original stereo worked fine. I have read on this topic in
the group and it seems that ground wire may be one of the reasons. I
connected the brown ground wire in my toyota harness correctly to the
ground wire in the stereo. There is another rear ground terminal on
the stereo to which I did not connect anything. Would that have an
affect.

I bought this stereo used, so it is possible that the internal amp may
be fried. Can I still use an external amp. If yes I have a very old
Alpine amp. Its model 3008. The wiring on the unit is as fllows:

One one side
2 pairs of speaker wires. One pair is grey with yellow line and the
other pair is green with yellow line. i.e. both wires is each pair
have the same colour.

One black wire
One yellow wire
one red wire

The other side of the amp has the following wires
One grey
One green
one Black
and one funny large back connector female.

Would greatly appreciate any help

Thanks

Regards
imran