DA 300 + TC

Just noticed Stefan - the contact marked * in your diagram above is not present on either of my non DA* lenses. That would suggest that it is an SDM related contact.

Don't think so Roger.
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On the body mount, the "*" contact is slightly recessed. On the lens mount, "*" is a small pin whose head can be raised or lowered depending on the position of the lens aperture ring. When a numeric f-stop is selected, the pin's head is lowered so that it does not make contact with body's "*" contact; when the "A" aperture setting is engaged, the pin's head is raised, and it makes electrical contact with the body's "*" contact.

Even if it is, the contact is needed for A lenses to work so the chance is very unlikely that that contact is causing the SDM not to work.
Everything is possible of course but don't think that one is it.

I also still believe that only the PZ and info contact is needed for SDM.
info contact to let the camera know it has SDM.
AND the two PZ contacts to power and control the SDM.
SDM is most likely a DC motor since the batteries deliver DC.
so one contact is + and the other - and if the motor needs the turn the other way you switch the polarities so that the current flows the other way and in effect making the motor turn the other way too.

To stop anyone else asking, the teleconvertor I offered for sale at the top of page 4 has been sold (to Oggy).

I hope you got a good price for it, as one of the very few teleconverters that work with SDM they are worth bucket fulls of cash (well ok, that may be a slight exaggeration).

I never use mine but wouldn't part with it .. just in case

We agreed a price based on Ebay prices. Yelvertoft posted it quickly and it was well wrapped.

I have had a couple of plays with it with some reasonable results and some not quite so good. It doesn't seem to like my DA* 300, but is not bad with the 60-250. Will update if anyone is interested.