Bummer!

I just finished machining a couple of big slots in the aluminum box, where the critical binding posts go, and added a polycarb plate that the terminal strips mount on. Now the leakage is showing about 100 fA, basically my measurement limit. It was ugly, machining the already-"finished" electronics. I tried milling it dry, but that didn't work, so I wound up getting chips and cutting fluid everywhere. Had to clean all that up.

It's amazing what a few drops of Tapmatic will do.

Here's the box:

ftp://jjlarkin.lmi.net/99A260A1.JPG

ftp://jjlarkin.lmi.net/99A260A3.JPG

ftp://jjlarkin.lmi.net/99S260A.JPG

Seems to work now.

John

Can they be fitted into a nylon shoulder washer?

No, that's 12nA. 12pA is 1/1000 of that:

Best regards, Spehro Pefhany

Now I'm seeing 0.0000000000001 amp. About 600K electrons per second.

Somebody could get rich selling special keyboards for googlegroopers, one with an LOL key.

John

"John Larkin" wrote in message news: snipped-for-privacy@4ax.com...

believe it or not.....

Cheers

One that shocks some sense into them would be nice.

What's with the huge bolts sticking out of the front? It'd look a lot nicer if you'd put the heads on the outside.

Too late now that you have your alternative solution but have you tried cleaning them ? 10 minutes in Safewash with ultrasonics and then rinse in de-ionised water. Since you are looking for better than 80G ohms don't breathe on them and do wear gloves.

Michael Kellett

That's to hold down the bent-aluminum measurement cover. At pA levels, just moving around in the vicinity of the box will slam the middle-node voltage around, and, unshielded, there's lots of 60 Hz there too. These sorts of measurements don't work in free air.

John

Oh, I see.

Certainly the type of plastic they use seems to have a kinda oily surface as they come out of the Rat Shack blister packs. Dunno if that's the binder post plasticizer vapor, or some sorta vapor from the blister pack, or just the environment in the packaging factory/city.

Tim.

Is it really the posts, or is it simply crud? Have you washed them with some kind of soap with no fragrances or hand lotions, or maybe with Tide, and rinsed them with DI water followed by minimum 70% IPA, and blown them dry with clean, dry, oil-free shop air? Don't use acetone - it will clean them all the way down to bare metal. ;-)

Good Luck! Rich

Doesn't humid air itself have that kind of leakage? ;-)

Cheers! Rich

Don't you mean, for the victims of the gg-ers? ;-)

Cheers! Rich

Geez, John, did you just fall off the turnip truck yesterday? I've been doing this sort of thing for decades. For steel, practically any ol' ordinay petroleum-based oil will work, and for aluminum lard, which in Mexicanese is "manteca". It works like a charm, albeit, as you've noticed, it makes mell of a hess, but you do get real purty results.[1] ;-)

Cheers! Rich [1] yes, I know it should be "really pretty", but I thought the way I wrote it here would be somehow more poetic, or amusing, or whatever. ;-)

What's wrong with Tapmatic Aluminum cutting fluid? A tiny bit is all it takes to cut cleanly. A tiny bit is also what it takes to gunk up my beautiful finished electronics.

We don't stock lard in the machine ship. It attracts ants.

John

RH is 63% here right now, and I'm seeing about 5 fA. That's 5 microvolts across a 1G resistor.

Plenty good enough for testing diodes and jfets.

John

I'd have just used a hole punch !