Stingray Special – Bad hum in Series mode

I recently bought a new Stingray Special 5H, but seem to have lucked out, as it has a bad earthing problem. When in either of the Series modes, if you touch a pole-piece, there is a really loud hum. (It’s worse in the centre/filter position.) The store got their tech to check the pre-amp and reckoned they “fixed something”, but I got it home and it’s just the same. Yes, I’ve tested it on various power outlets and the problem always occurs, but does vary slightly in volume.

Anyway, I’m pushing the store to get me a replacement pre-amp from the distributor, but I thought I’d ask if anyone has experienced this before.

Cheers,

EG