Thanks once again for your help!
Unfortunately a direct replacement is not possible. A big problem we have in this country is that people import and sell items for which there is no supply chain for spare parts and the seller has no intention of providing spare parts. This is yet one more example.
To make matters even worse many items which are sold here are strange models which are not sold in the US. So even though the item might be an authentic name brand product, such as Yamaha, Honda etc. the items are not in the US representatives database, so the items can't be looked up to find even a cross-reference.
Often when I Google the model numbers of equipment sold here often the only search results are in Russian or an Asian language. I think many times the items sold here are things which don't meet US or European emissions standards so that's why the items are not listed in US databases.
All let's say we've exhausted all resources and can't find a direct replacement for the AVR. We've been told that even though the generator is branded Yamaha it's really a Kubota, but even that was no help. So it's going to have to be a generic replacement.
Happily there's nothing else connected to the external terminals you mentioned above (Go and Gu, terminals four and 200). Those connections come out to a terminal block but nothing is connected to it
I'm hoping that just the DC resistance of the exciter is good enough. I don't have equipment to check the AC resistance. Is DC resistance good enough?
Thanks again!
Greg