Thank's Bob for an excellent diagram, now I see where I went wrong.
I should have stayed up on the roof.

NJ, you actually built one, from tested components, ran an experiment, photographed it and posted it to ECN???
You crazy person! LOL! [Linked Image] [Linked Image] [Linked Image]

Alan

[ ps. Still like to see the math. proof for that central 6-resistor group; I can't work out why it comes to 1/6 ohm. ]

Wood work but can't!