ESP LTD - upgrade or unburden?

[forensis]

I have a ESP LTD B205SM fretless and would like some advice on a problem. The problem is that my top string (high C in this case) has almost no sustain or tone compared to the other strings. I have tried many things (and strings) to resolve this without success. It's come to the point where I need to upgrade it or part company with it. I'm wary of investing what might amount to a couple of hundred quid with no guarantee of success and was hoping for some views on advice one way or the other. 

[itu]

Put the bass to the table. No amp. Pluck an open G and compare it to that open C. Is there something wrong with the bridge or the saddle? If these are OK and the sustain is in the same ballpark, then continue to the electronics.

Is the pickup height comparable (in output) to the other strings. If not, raise the C side. You may be able to adjust the string height slightly to adjust the levels a tiny bit but remember to check the fine tuning after that.

If these do not help or you are not able to do the adjustments, turn to a local luthier.

[forensis]

Thanks this sounds like a useful suggestions to narrow the source of the problem and one that hadn't occurred to me. I have tried it but there is too much noise in the house at the moment to make a judgement so will repeat the test later this evening when things are quieter.