I recently picked up a Sony Dual cassette 4-band tuner boombox model
CFS-w365s for a song at a consignment shop. This possibly decade-old
portable dustbin turned out to be in perfect shape with a lot of
cleaning and shots of compressed air. I then cleaned both tape decks
and de-magged the play heads.

Both played crisp and clear until two days later, the left(Play Only)
deck lost all it's treble! I performed a quick azimuth alignment on
it, recovering just a little treble. It is still dull compared to the
right(play record) deck.

I then jiggled the cassette in the well and pushed and pulled on the
head(gently of course) and wiggled the wires to the play head - none of
this affected the sound - adversely or otherwise.

What else could cause loss of high-frequency response like that?
Thanks for any tips.

-ChrisCoaster
"Keepin' the old school alive!!"