So, I bought the Hamer... There seems to either be a short, issue with the ground or the input jack needs replacing (at least from what I've been able to ascertain). I can't see any ground issues, so I will be replacing the jack first (probably should be done anyway).
I have taken it apart and took some photos, it seems like it's 100% original, the person from who I bought it said her husband bought it brand new in ~1997. She has a bit of work I believe, fretwork, electronics etc. The pots are cor-tek 500k and the 5 way switch is also cor-tek. I believe the bridge to be a wilkinson type? Sperzel style tuners should just drop in and the nut seems to be plastic.
I just couldn't help myself, she felt good when I picked her up