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Re: differential probes



Original poster: "jimmy hynes by way of Terry Fritz <teslalist-at-qwest-dot-net>" <chunkyboy86-at-yahoo-dot-com>

Hello,

The PCB file is on my site 
<http://www.hot-streamer-dot-com/chunkyboy86/diffprb.pcb>www.hot-streamer-dot-com/chunkyboy86/diffprb.pcb 

There are also some pictures of it 
<http://www.hot-streamer-dot-com/chunkyboy86/diffprb.jpg>www.hot-streamer-dot-com/chunkyboy86/diffprb.jpg
www.hot-streamer-dot-com/chunkyboy86/diffprb2.pcb

Someone should probably check it for errors, and either tell me about it or 
fix it and give me the new file.

One thing that worries me is the BNC connectors. There could be up to 3600 
volts across the pins, and it doesn't look like it can take it. Should both 
connectors be female, and just plug it into the scope through an extension? 
It seems like the only way to do it with two channels

I changed the switch slightly, the one I was planning on getting will fit 
in the circuit board, or it can be connected the way Terry was planning. If 
everything looks ok, I'll order some boards and parts tomorrow afternoon.


--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "jimmy hynes by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <chunkyboy86-at-yahoo-dot-com>
 >
 > Hey everyone,
 >
 > I'll lay it all out tomorrow so you guys can check
 > it.
 > With the surface mount chips, it is probably better
 > to
 > skip the prototype and go straight to the PCB,
 > agree?
 > The PCB has a two day turnaround, so I can probably
 > get them built by the end of the week. Who wants to
 > try one?
 >
 >
 > --- Tesla list <tesla-at-pupman-dot-com> wrote:
 > > Original poster: "Terry Fritz"
 > <teslalist-at-qwest-dot-net>
 > >
 > > Hi Ken,
 > >
 > > At 09:53 PM 7/13/2003 -0500, you wrote:
 > > >On Sun, 13 Jul 2003, Tesla list wrote:
 > > >
 > > > > Original poster: "Terry Fritz"
 > > <teslalist-at-qwest-dot-net>
 > > > >
 > > > > Hi Jimmy, Finn, and All,
 > > > >
 > > > > This is the present schematic and parts list
 > I
 > > have in mind for the
 > > > > differential probe. I have NOT assembled or
 > > tested it yet!
 > > > >
 > > > > http://hot-streamer-dot-com/temp/DiffProbe-5.gif
 > > > >
 > > > > http://hot-streamer-dot-com/temp/DiffProbe-5p.gif
 > > > >
 > > > > It is still just using the basic 150MHz TI
 > > THS4151ID differential
 > > > > amplifier IC and other straight forward
 > parts.
 > > > >
 > > > > One thing I am "trying" to add is a front end
 > > that can take a hard hit. I
 > > > > will have a system ground stud and MOVs at
 > 1800
 > > volts each. These will be!
 > > > > fused with low current but high voltage
 > fuses.
 > > The idea is if you get a
 > > > > say 20,000 volt cap on the input, the MOVs
 > will
 > > clamp it and the fuses will
 > > >
 > > >How about some neon lamps or one of those glass
 > or
 > > ceramic tubes the size
 > > >of a pencil eraser with metal leads? Both should
 > > have a low capacitance,
 > > >and don't conduct until 70 volts or so for neon,
 > > and several thousand for
 > > >the larger ones. Maybe put them both in
 > parallel.
 > > You probably want the
 > > >lowest possible impedance in a short mode,
 > > otherwise the probe or what's
 > > >left of it will dissipate lots of heat, which
 > leads
 > > to it blowing up or
 > > >catching on fire. Large energy storage caps are
 > >! designed this way- to
 > > >short out with the lowest impedance so their
 > energy
 > > is dissipated outside
 > > >the cap tank in bussbar and fuses, not inside
 > where
 > > the tank will build up
 > > >pressure and rupture. MOVs are basically
 > > firestarting kits.
 > > >
 > > >KEN
 > >
 > >
 > > I have a "bunch" of Victoreen SGCA-2500D spark
 > gaps:
 > >
 > > http://hot-streamer-dot-com/temp/P7130038.jpg
 > >
 > > The 2500 volt firing voltage is sort of high.
 > But
 > > not a big deal here if I
 > > put them in parallel with the MOVs... I am
 > hoping
 > > the "fuses" will break
 > > the current before any fires start...
 > >
 > > Jim also mentions the Sidactors. I think I
 > remember
 > > of few of them blowing
 > > up in my ! face in the early 90'S :o)) But they
 > are
 > > also another great
 > > possibility in this case!!
 > >
 > > Cheers,
 > >
 > > Terry
 > >
 > >
 > >
 >
 >
 > =====
 > Jimmy
 >
 > __________________________________
 > Do you Yahoo!?
 > SBC Yahoo! DSL - Now only $29.95 per month!
 > http://sbc.yahoo-dot-com
 >
 >


Jimmy


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