Forget cleaning your DIN plugs/sockets - it’s the 4mm speaker outputs/inputs you need to pay attention to.
The distortion trace on an oscilloscope has to be seen to been believed when these sockets are dirty.
I’ll get some pictures to back up my claim in due coarse.
Cleaning these is a gamble, because the best way is to use a cotton bud soaked with isopropanol & the head is liable to come off, leaving you with a headache!
For those willing to take the risk - insert the cotton bud first dry, using a rotational force, then soak the same bud with isopropanol & repeat the cleaning action. If the head remains on the stick, the filth that comes out may surprise you!
Regards
Neil.