An unusual Oscilloscope phenomenon

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Check out a rather unusual phenomenon you can see on your oscilloscope in my
latest blog (#14):
http://www.alternatezone.com/eevblog /
See if you can get it to happen on your scope!
I'll offer a free subscription to my blog for the best screen shot posted
:->

Oh, and the probe doesn't have to be shorted either.

Have fun.
Dave.
--
================================================
Check out my Electronics Engineering Video Blog & Podcast:
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Re: An unusual Oscilloscope phenomenon


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Got it immediately, because I once worked in lab that had cheap plastic
chairs that generated 1cm sparks when you stood up!

--
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
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Re: An unusual Oscilloscope phenomenon


On Thu, 25 Jun 2009 03:49:50 +0100, Dirk Bruere at NeoPax

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Back in the old days, they used to generate 1/2" sparks.


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Nasty stuff that Bakelite.



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Goes nicely with wood cases:

http://ip.co.za/shop/images/wheatstone.jpg
http://www.surplussales.com/Images/Equipment/TestEquipment/Leeds-Northrup/eqp-wbm-119828/eqp-wbm-119828_lg.jpg



Re: An unusual Oscilloscope phenomenon



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http://www.surplussales.com/Images/Equipment/TestEquipment/Leeds-Northrup/eqp-wbm-119828/eqp-wbm-119828_lg.jpg
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When I started out with a government run telco and some of the gear was
still in nice wooden cases. Over the years I saw pallet loads of test gear
consigned to scrap. Loads of bridges, wood cased multimeters and bakelite
AVO meters. These things sell for quite a few dollars nowadays - aint
hindsight nice!




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http://www.surplussales.com/Images/Equipment/TestEquipment/Leeds-Northrup/eqp-wbm-119828/eqp-wbm-119828_lg.jpg
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Bad focus but shows the concept, when I was a teenager I made almost
everything in wood, nicely polished, several layers of laquer, some more
polishing:

http://www.analogconsultants.com/ng/images/oak2.jpg

I usually spent a lot more time on the enclosures than on the
electronics but the stuff is still working.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: An unusual Oscilloscope phenomenon


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Didn't anyone tell you that dovetail joints were optional? :-)

Just kidding.  I can't imagine even you would have chiseled out dovetail
joints (since I'm thinking those dovetail jigs you use with a router didn't
exist for the casual home woodworker back then)...

I built a small table (~2'x2'x1') for test equipment to live on not quite a
month ago.  I thoroughly enjoyed using a dado blade to cut a bunch of lap
joints, and verified the table could hold 300lbs.  Old boat anchors, here I
come!



Re: An unusual Oscilloscope phenomenon


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I didn't go that far but I polished and stained the corners until you
couldn't really see where things butted up anymore.

Saw a contractor commercial lately about the Fein Multimaster. Drooling
all over the place. Fein is "the" electric tool company in Germany, only
the good stuff. You had to call a 1-800 number to find out the price and
that should have been a dead give-away. Well, found it on the Internet,
saw the prices of spare inserts and decided that I do not need it this
urgently.

(Amazon.com product link shortened)


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That's the other thing I built, or partially had built when I was around
15, size 6ft by 4ft and extremely sturdy (boat anchor proof). I made a
drawing of the frame and asked my parents whether it was ok to get some
metal stock, borrow a welding transformer and weld it in the garage. Oh
no, no dice. So I went to the local HW store, a larger kind of mom and
pop place. My classmates said they'd laugh at me there. The foreman took
a look, "Yep, will be ready in two days, then we'll drive up there and
chuck the frame over the hedge and you come down here to pay us the 70
Deutschmarks". They didn't even want up front cash. Oh, now my chest
swelled and I felt like an engineer. Until I glued the formica onto a
panel that would become the top and I had it slightly skewed ...

--
Regards, Joerg

http://www.analogconsultants.com /

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I guess nobody told you about the shims. ;-)

Cheers!
Rich


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No shims. The trick is to lay the Formica upside down onto the floor,
butter it up with glue, then lay the wood piece on top. While doing the
latter it slipped my hand and ... thud, landed on the Formica. Almost
perfectly line up. With the emphasis on "almost". There was no way to
get this off because it was the Henkel Pattex type glue which never lets
go of anything.

--
Regards, Joerg

http://www.analogconsultants.com /

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How do shims fix a skewed veneer?

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You put the glue on the surface and let it dry, and lay thin pieces of
wood across it. Put the glue on the formica, let it dry, and lay it
on top of the shims. The shims have no glue, so don't stick. Line
the formica up, on top of the shims, and one by one take the shims
out and let the formica stick to the surface.

I've seen it done on those "home improvement"-type TV shows. :-)

Cheers!
Rich


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With a fresh can of Henkel Pattex glue the shims may never come out again.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: An unusual Oscilloscope phenomenon


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Well, then I guess using Henkel Pattex glue isn't all that great an idea. ;-)

Use just plain ol' ordinary common off-the-shelf "contact cement", and
let it DRY before you start placing the shims. Come to think of it,
when I was a video game tech, the shipping guy used to do it to the
sides of video games when they'd convert a cabinet from one game to
another.

Cheers!
Rich


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They don't fix it - they prevent it. You contact cement the
veneer & the top and let the cement dry. Lay shims on the top,
lay the veneer on top of the shims. Line the veneer up properly,
then withdraw the shims one at a time, pressing the veneer down
onto the top as you go.  You cut the formica before you start,
such that it will hang over the top by about 1/4" on all edges.
After sticking the formica to the top, you use a router to trim
the formica to be exactly even with the top on all edges, with a
bit of a bevel on the dege of the formica.

Ed

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I first saw the Fein Multimaster at the Portland Woodworking Show not that
long ago.  They were having a grand time demoing it -- and letting anyone who
cared to try it out themselves -- and it was *very* tempting.

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There's been a lot of competition with it lately (apparently Fein's patent
expired?):

Rockwell:
(Amazon.com product link shortened)
(looks really good)
Dremel:
(Amazon.com product link shortened)
(dunno)
Habor Freight (!):
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber65%700 (you're
lucky if you get what you pay for?)

...and there's always eBay for knock-off Fein inserts... (quality level... who
knows?)

Nice story about getting your workbench frame built.  I suspect that just
couldn't be done today, unfortunately. :-(

---Joel



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(Amazon.com product link shortened)
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Alright! Thanks. I guess I do have to check out Harborfreight.


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No, the HW store closed. The usual, the 3rd generation drove it into the
ground :-(

--
Regards, Joerg

http://www.analogconsultants.com /

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(Amazon.com product link shortened)
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Interesting.  I was intrigued by this just last month and
meant to look into it:

Fein:
   www.4multimaster.com

--
Cheers,
James Arthur

Re: An unusual Oscilloscope phenomenon


Almost forgot... Bosch has a rechargeable version, but the reviews are mixed:
(Amazon.com product link shortened)
(which is really too bad... you might recall the discussion about the little
Bosh impact drivers --  
(Amazon.com product link shortened)  
-- and how they're a very, very good tool...)





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