its very used, its a 1985 model
my headphones work in all my other devices
id probably assume its the wiring or something of that nature involving audio, not to mention its "very used" and a "1985 model"p sure its the walkman itself and not your headphonesalso, did it come in proper packaging or just a DIY one?
1 question: do your headphones have a microphone/volume adjuster attached? If so, that could be the reason but I'm not entirely sure.