Help - Noisy GT sm5

[beerco]

Hi there new to the forum and was hoping to find a little help,

I'm looking at buying a used Groove Tubes sm5 off a buddy of mine. He let me borrow it first to check it out and it's got a noise problem. The mike sounds fine but has a noise pop type of thing that comes in every few seconds.

Here is a link to a recording where the noise is very obvious:

Does anyone have any ideas as to where this noise is coming from and whether it's something thats easily fixable?

thanks,

 

[beerco]

Oh, wanted to add, I've tested two other condenser mics and they don't have this noise so it's definitely it and not the downstream devices.

Thanks