MVS 1 Slot - Puzzle Bobble - No Sound!

I have 3 puzzle bobble carts now, two appear to be bootlegs, one appears to be legitimate, and the sound does not work on any of them. On one of the bootlegs the sound worked up until about 6 months ago where it just stopped working.

All other games/carts the sound works flawlessly, and the sound works fine in the hardware test.

Any ideas? Thanks!
Stephen

clear backup ram if that does not do it -> clean the carts + the slot - sounds really like a backup ram or dirty cart/slot prob

I had exactly the same here. Bought a Puzzle Bobble off eBay with "no sound" for $10. Cleaned the card-edges... sound!