[Uncle Bulgaria]

Thanks all. I've discovered that the noise I was hearing during testing tape playback was because the two tape guides before and after the heads were at the wrong height. They consist of a couple of threaded shaped end caps which can be screwed up and down relative to the top plate with a brass bushing in between. The tape was rubbing too much on the top or bottom of this.

I've decided the left-hand motor spindle is too high, so the guide was pulling it down. I wondered why there were some washers under the motor standoffs, and now I think that they were for setting the height of the tape from the top plate. I'll put them back in...

BillDWVA - that's perfect, thank you! It looks like this is is a modification I need to do. The switch in the manual must be a more complicated later version. Does your Vortexion have the L-shaped pressure pad or a felt one?

TIMTAPE - I think re-lapping is next, and then I'll have to struggle with head tilt. The head sits over a rod to allow it to rock sideways, but is connected by four screws. Thus it's possible to overtighten them and bend the base over the rod, affecting the forward/back alignment. This is what's happened with mine and become obvious when I was reassembling it, so I'll have to flatten the base in order to have a, err, baseline. I don't suppose there's any easy way to check for squareness against the top-plate.