A quick request for advice from the many instrument repairers/builders who I know hang around here.

This last summer I bought myself a cheap flat-top mandola. The action was appallingly high, and the frets were uneven so you couldn't play above the 10th fret. To get it working, I fixed the worst of the unevenness in the frets, and brought the action down from the stratosphere (but still pretty high). Then over Xmas, I decided to sort it out properly. I've filed the frets so they're all equal heights, bought a better bridge and reduced the action to a good playable height, so it's a much more user-friendly instrument. But here is where things started going wrong.

Before, the frets were only catching at the 10th fret and above. With the rework, they were catching at the 6th and 7th frets. I put a ruler on the neck, and found the reason - where a guitar neck would have a little curve in it from truss-rod or carving, the neck on this mandola is dead straight! So of course, the further up the neck you get, the narrower the gap beteen frets and strings, and everything starts catching. It seems that the only thing stopping that happening before was the insanely high action.

Unfortunately this is a cheapo instrument (a "Blue Moon" from Hobgoblin, for reference). I don't think it's got a truss-rod (there's no cover above the nut, and I can't feel anywhere where a truss-rod would be adjusted inside the soundbox) so I can't tweak this. So, as I see it I have three potential courses of action. One is to raise the action slightly and accept that as the cost of playing the instrument. The second is to progressively file down the upper frets so they don't catch. And the third is to do both. :-/

What do people think? Has anyone seen this kind of problem before? I'll probably go for number three, raising the action as much as I can live with and trying to file the frets down as little as possible, because that seems like the lowest-impact work. But do you reckon I'm likely to be able to turn it around and get it good and playable, or is it inevitably going to be a bit nasty?

Cheers,

Graham.

PS. There is always the fourth option of a new instrument, but I'd rather not go that route. Surprisingly for the cost (£60), it has a solid spruce top and the sound from it is very good - loud and full of tone. I suspect I'd have to be paying many times more for something that'd sound noticeably better, so I'd rather patch up the one I've got.