Panasonic Minidisc Player SJ-MJ15: Very low left audio channel

Hi,

I have 2 MD players from Panasonic (type SJ-MJ15, very stylish). One or them works well, the other one has a sound balance problem: The right channel is louder than the left one. There is no balance control knob on the units.

I tried the same MD in both, tried the same earplugs and the same remote, cleaned the lens, but the problem persists.

Any idea what could be done to fix that?

Thx in advance,
Stefan B.