Thanks to some help from fixya.com...

Remove grates, burner rings and knobs, shut off gas, unplug cooktop, remove whatever is holding down your cooktop to the counter, and dismount the cooktop. Set the cooktop down supported so it's fairly level, and unscrew the brass rings in the middle of the burners. They have two small opposed notches to put some kind of something in to turn them counterclockwise. I used a couple of putty knives and a gasket scraper like spanner/screwdrivers. BTW, make sure you remove the cooktop before you disassemble...if you release the top with it in the countertop, it will fall through (no, I didn't do this, but almost). Also watch the o-rings under the burner bases. They get brittle from the heat, I guess, and break easily.

More disassembly info...

There is an aluminum coupler between the burner bases and the venturi tube. It is technically part of the venturi tube, but I had one unscrew there instead of at the brass ring. You can still disassemble the cooktop, even if they ALL do this, but you will need to separate this coupler from the brass ring in order to change out the burner bases. No big deal, just a LITTLE penetrating oil on the threads, a pair of chanel locks on the back, and turn it out carefully. If your cooktop is older, and there is a lot of corrosion on these threads, it might be difficult here... When you get the coupler out, re-install it onto the venturi tube. I used a LITTLE regular gas pipe plumbing thread sealant on these threads, as it seemed there was something on there originally...I don't know if this is the right thing to use, probably not.

My switches all check out good with the multimeter, but looks like I have one bad piezio element. Hopefully that will fix it.

Update...can't get just the piezio ignitor element from Viking, must buy the whole burner base. Ridiculous, since I can see the c-clip that is holding it in, and i know these are an off-the-shelf item supplied to Viking by and outside vendor, I just don't know where to get them. The burner base is $28, instead of replacing a $1 part... Also, if you are replacing, or even removing burner bases, you will probably want new o-rings. They look like high temp silicone to me, and Viking gets between $5-$8 apiece...ouch.

Re-assembled cooktop, left unplugged, waiting on parts...

John

Nice find on those ignitors, that may save me some money some day. New electronic controller working fine since repairs. No more flooding the cooktop to clean...bad for electronics...it is not as "sealed" as they lead you to believe, probably due to those o-rings drying out and cracking. Soakdown with simple green, let stand, and wipe off with damp cloth, repeat as necessary, works better anyway.

John

I have an oven under the cooktop, so I think nothing should fall through, right? do you have a diagram of the spark module location and how to access it? Thanks!