I've got a Hohner Chromonica 270 (II, I believe) in C that's about 20 years old, but in good condition. All of a sudden, something went wrong with the F at the 10th hole (without the slide) and started sounding more like an E. An F (or E#) is the blow note with the slide, so the harmonica was still playable, but that wasn't ideal.

So, I took it to my local music store. They have an arrangement with some workshop. They'd done a minor repair on it before when I couldn't get the slide assembly adjusted. It wasn't expensive and I was happy with the result.

This time, the harmonica came back with an F where the E should be and a very sharp Eb where the F should be (the notes without the slide)! So, instead of being fixed, it's worse than before and not really playable anymore.

Does anyone have any suggestions about what I could do? I've been told that sending it in to Hohner is usually too expensive to be worth it. I know a harmonica isn't a permanent instrument, and after 20 years this one doesn't owe me anything. However, I can't afford to replace it and it's otherwise in good condition. It's not perfectly in tune, but not badly out-of-tune, either.

Any advice would be much appreciated.