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What's this component?

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Wipf

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Oct 3, 2012, 4:31:13 PM10/3/12
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Hi,
I'm a lurker here and I thought I'd ask for some help. I have a few
boards I saved from the trash that appear to be little HV supplies for a
mass spectrometer. I was trying to trace through the circuit and could
not figure out what these components were on the (presumably) multiplier
part of the circuit. A picture is here
http://www.flickr.com/photos/dwipf/8051484989/in/photostream
They look like diodes but don't read as diodes on my multimeter (maybe
because they are in circuit). They are marked as 00B or OOB which
doesn't seem to be any diode code that I can find.

Any thoughts?

Thanks
David


tm

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Oct 3, 2012, 5:22:25 PM10/3/12
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"Wipf" <wi...@ra.msstate.edu> wrote in message
news:MPG.2ad65c8e6...@nntp.msstate.edu...
It is a HV multiplier. A X3 positive multiplier on the left side and a X3
negative multiplier on the right.

Look up Cockcroft-Walton multiplier on google for much more detail.

Jon Elson

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Oct 3, 2012, 6:53:02 PM10/3/12
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I can trace the wiring right through the board in your excellent photo.
They HAVE to be the rectifier diodes, but due to the application, they may
be multiple stacked dies to get more reverse Voltage. That may defeat
your meter.

Jon

Wipf

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Oct 3, 2012, 6:18:06 PM10/3/12
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In article <k4ia3a$ips$1...@dont-email.me>, No_on...@white-house.gov
says...
Thanks, I think it is a multiplier but my question is specifically about
the "diodes" marked 00B. I couldn't find any info on their specs and, in
fact, don't read as diodes using my DMM.

David

tm

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Oct 3, 2012, 7:29:04 PM10/3/12
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"Wipf" <wi...@ra.msstate.edu> wrote in message
news:MPG.2ad67594a...@nntp.msstate.edu...
They are high voltage diodes and have a large forward voltage drop. Maybe up
to 10 volts or so. They are made up of many series diode junctions in order
to get the high reverse voltage needed.

Try forward biasing to diode through a current limiting resistor with maybe
24 volts and 10 k ohms. Measure the forward voltage drop across the diode.
You can do this in circuit.

Tm




gregz

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Oct 3, 2012, 8:00:13 PM10/3/12
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Try something RX 1K or higher to get more voltage. Depends on the meter,
some have nine volt batteries on high ohms.

Greg

Martin Riddle

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Oct 3, 2012, 8:17:41 PM10/3/12
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"tm" <No_on...@white-house.gov> wrote in message
news:k4ihfm$21j$1...@dont-email.me...
if you have a simpson 260, there is enough voltage to get the meter to
move a bit ;)

Cheers



tm

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Oct 3, 2012, 8:34:06 PM10/3/12
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"Martin Riddle" <marti...@verizon.net> wrote in message
news:k4ikj9$h87$1...@dont-email.me...
Those little diodes don't have very many junctions so you would be right.
Some of the >10 kV diodes drop 10 -15 volts (or more) forward. I still use
my 260 but you need to be careful. It can do a pretty high current for some
solid state devices now days.


Jan Panteltje

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Oct 4, 2012, 5:00:02 AM10/4/12
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On a sunny day (Wed, 3 Oct 2012 15:31:13 -0500) it happened Wipf
<wi...@ra.msstate.edu> wrote in <MPG.2ad65c8e6...@nntp.msstate.edu>:
That looks like a voltage multiplier,
must be diodes.
Some diodes do not simple measure .7 V or as 'diode',
some HV diodes are in fact many diodes in series,
and would not show any reading,
this looks like Ge diodes, if so would read a lot lower and perhaps leak in reverse.
Take one out and show us some numbers (I versus U).

Lord Valve

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Oct 4, 2012, 9:27:59 AM10/4/12
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Multiple-pellet stabistors.

Lord Valve



Don Lancaster

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Oct 4, 2012, 12:00:49 PM10/4/12
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On 10/4/2012 2:00 AM, Jan Panteltje wrote:
> On a sunny day (Wed, 3 Oct 2012 15:31:13 -0500) it happened Wipf
> <wi...@ra.msstate.edu> wrote in <MPG.2ad65c8e6...@nntp.msstate.edu>:
>
>>
>> Hi,
>> I'm a lurker here and I thought I'd ask for some help. I have a few
>> boards I saved from the trash that appear to be little HV supplies for a
>> mass spectrometer. I was trying to trace through the circuit and could
>> not figure out what these components were on the (presumably) multiplier
>> part of the circuit. A picture is here
>> http://www.flickr.com/photos/dwipf/8051484989/in/photostream
>> They look like diodes but don't read as diodes on my multimeter (maybe
>> because they are in circuit). They are marked as 00B or OOB which
>> doesn't seem to be any diode code that I can find.
>>
>> Any thoughts?
>>
>> Thanks
>> David

That is called a "nomenclature".



--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: d...@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com

Wipf

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Oct 4, 2012, 4:02:09 PM10/4/12
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In article <k4ihfm$21j$1...@dont-email.me>, No_on...@white-house.gov
I can do that. It sounds like that's the consensus on them. I wasn't
aware that HV diodes had such a large Vf.
Thanks
David

Wipf

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Oct 4, 2012, 6:24:38 PM10/4/12
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In article <k4jj70$fai$1...@news.albasani.net>, pNaonSt...@yahoo.com
says...
I have posted curves here, the Vf is about 12 V at 20 mA but the curve
is non exponential.
http://www.flickr.com/photos/dwipf/8054927724/in/photostream (log)
http://www.flickr.com/photos/dwipf/8054927808/in/photostream
http://www.flickr.com/photos/dwipf/8054927621/in/photostream (linear)

For comparison, also the 1N4005 diode and a BYV-27-200 Avalance diode
also on the board.


gregz

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Oct 4, 2012, 7:03:08 PM10/4/12
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I blew out a large photodiode with a triplet. I was able to see the contact
wire blown like a fuse.

Greg

Jan Panteltje

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Oct 5, 2012, 6:24:36 AM10/5/12
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On a sunny day (Thu, 4 Oct 2012 17:24:38 -0500) it happened Wipf
<wi...@ra.msstate.edu> wrote in <MPG.2ad7c8a5d...@nntp.msstate.edu>:
Very nce, indeed looks like diodes in series, because of the high value where it starts conducting.
The old TV HV diodes (for 4 kV focus, and also 18kV BW), had many small selenium? disks in series in a ceramic tube,
I opened one once that was defective, lots of small round disks.



>http://www.flickr.com/photos/dwipf/8054927808/in/photostream



>http://www.flickr.com/photos/dwipf/8054927621/in/photostream (linear)
>
>For comparison, also the 1N4005 diode and a BYV-27-200 Avalance diode
>also on the board.

Very nice measurements, reminds me of my student time... :-)

Phil Hobbs

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Oct 5, 2012, 12:05:33 PM10/5/12
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Photodiodes are often much more vulnerable than one would expect from
their size, because the epi has to be so thin that transverse voltage
drops give rise to current crowding near the contact. "Blue enhanced"
ones are worse than the ordinary sort.

The best way to measure photodiode polarity is to look for the
photovoltage. Second best is to measure the photocurrent.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

gregz

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Oct 5, 2012, 10:29:15 PM10/5/12
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I measured the short circuit on r1 on the triplet. 100 ma.
The owner of the diode sort of frowned when I discussed what happened.

Greg

Phil Hobbs

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Oct 5, 2012, 10:50:11 PM10/5/12
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Oops.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

gregz

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Oct 5, 2012, 11:09:10 PM10/5/12
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I'm glad I never tried that on the 16 X 16 matrix centronix sensor we used.

Greg
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