How to adapt small ring flash to bigger lens?

Question

I have a ring flash from sometimes between '70s and '90s, it is a Euro Blitz V60 PK (PC sync, no hot shoe).

The diameter of the thread is 52 mm and I could use it with my Nikon 35 mm F1.8 DX, but not with my Sigma 17-50 mm F2.8 DX (77 mm filter diameter).

Is there a way to adapt it? I can also consider DIY if I find good projects (like off-axis with simple light guides).

Edit

I am aware of the different trigger voltages and I will be careful not to fry my dSLR.

Edit 2

Well the internal circuit blew up due to leaks from capacitors and the usual white spongy deposit everywhere. Still, the question stays valid.

About the question: apart from a stepping down adapter, is there a way to expand the radius of the ring, by using something like http://photo-tips-online.com/review/ray-flash-ring-flash-adapter/gallery.php?id=ray-flash-ring-flash-adapter-full but from small ring to bigger ring, instead of from popup flash to ring flash (as in the link)?

Answer 1

You could certainly adapt it with a step-down ring. But you would be obscuring the outer part of the lens. This will be less of an issue at 50mm rather than 17mm and at narrower apertures. You will have to try it and see. Stepping rings are cheap:

http://www.ebay.com/itm/RISE-UK-77mm-52mm-77-52-mm-77-to-52-Step-down-Ring-Filter-Adapter-black-/161850448738?hash=item25af09db62:g:MOwAAOSwT5tWL2zZ