Self made Diode Tester or Fluke Scope Meter Component Tester...

[slampen]

Hi,

In the good ol' days I had a nice little circuit with a small mains
transformer and a resistor which I connected to my oscilloscope X and Y
input. This displayed a horizontal line at the scope. When I connected
a good diode between the 'Test Leads' from this circuit it displayed a
right angled 'L' and if the diode was shorted it displayed a vertical line.

Today I have a Fluke Scopemeter 99B and I thought its 'Component Tester'
mode was something similar, but I did not immediately understand how it
was supposed to work, neither do I have a manual for the Scopemeter.
Can someone here explain hos this 'Component Tester' is supposed to work?

Furthermore, does anyone have the schematic to a simple 'diode tester'
for an X-Y scope as explained above?

Does it exist something similar to this current vs voltage display but
with with three test leads to connect to a transistor's CBE pins and
cycle round all transistor leads three combinations (CB, CE and BE)
displaying the current/voltage diagram for each of the transistor's
'junctions'.

Any other transistor tester module available which can connect to a XY
scope or a computer and give me the 'graphs' without having to connect
two leads at a time...?

Thanks for comments on this

Geir

 

[mike]

Hi,

In the good ol' days I had a nice little circuit with a small mains
transformer and a resistor which I connected to my oscilloscope X and Y
input. This displayed a horizontal line at the scope. When I connected
a good diode between the 'Test Leads' from this circuit it displayed a
right angled 'L' and if the diode was shorted it displayed a vertical line.

Today I have a Fluke Scopemeter 99B and I thought its 'Component Tester'
mode was something similar, but I did not immediately understand how it
was supposed to work, neither do I have a manual for the Scopemeter.

Only because you didn't waste the 10 seconds to type it into google.
http://www.opweb.de/model.php?id=339

Can

someone here explain hos this 'Component Tester' is supposed to work?

Furthermore, does anyone have the schematic to a simple 'diode tester'
for an X-Y scope as explained above?

The concept of a curve tracer is trivial. You described exactly how to
do it
above.
The devil is in the details...variable voltages, current limits,
current step generators, and on and on and on.

There are a zillion curve tracer pages. Google is your friend.

I went thru the exercise of trying to build a curve tracer by
using a uC to generate fixed voltages and currents, then the A/D
to read the result and plot the points. Works in concept, but the
device temperature changes between measurements and the curves came
out all wonky.
Ain't no substitute for a good ole Tektronix 576. Does everything
you'd ever want, including helping you drive in the snow if you
stow it in your trunk...assuming you can lift it that high without
getting a hernia.

 

[slampen]

Den 01.01.2011 20:27, skrev JeffM:

[...]transistor tester module available which can connect to a XY scope
or a computer and give me the 'graphs'[...]

http://octopus.freeyellow.com/octopus.html

Anyone knowing how a curve tracers curves should look like for a Power
N-FET transistor??

regards Geir

 

[slampen]

Den 02.01.2011 22:28, skrev Jim Thompson:

There are better curve-trace adapter designs out there... IF you
really are intent on doing serious testing.

I want to have a quick and dirty way to check if components are okay or
not. However back in those days (70-80s I only worked with bipolar
transistors, hence I wondered how the curves would look like with a FET,
or do I risk to fry the gate..?

Geir

 

[mike]

Den 02.01.2011 22:28, skrev Jim Thompson:


I want to have a quick and dirty way to check if components are okay or
not. However back in those days (70-80s I only worked with bipolar
transistors, hence I wondered how the curves would look like with a FET,
or do I risk to fry the gate..?

Geir

There's a thing called the Huntron Tracker.
I never had one, but they appear to be much like what's already been
described. They're SERIOUSLY OVERPRICED, but a little research
might enlighten you about what kinds of tests are useful.
If I understand the manual to your scope, it can do a similar
function up to 3V.

The Tektronix 5CT1/7CT1 are nice plugin curve tracers.
Two drawbacks.
They're expensive cause there are not many for sale.
The mainframe is huge.
Good idea if you already have the mainframe. If you don't
have the mainframe, not so much.
I still have one sitting on my bench, mainly 'cuz I'm afraid
I'd hurt myself trying to get it up into the attic.
Tek 576 is the granddaddy of curve tracers. Can do 10A or 1500V,
thankfully, not at the same time or I'd probably be on fire by now.
I use mine more
for blowing shorts out of NiCd batteries than for testing transistors.


For bipolars, your ohm-meter will tell you if they look like two diodes.
If so, they're probably good. Yes, there are many failure modes that
don't show up that way, but as a percentage of cases you'll encounter,
one or both junctions are either blown open or shorted. Of course,
everybody wants to test in-circuit. Can sometimes do that if you know
the circuit. Typically, you don't and have to take 'em out anyway to be
sure.

FETS are a bigger problem. Other than checking for shorts, I've not found
any useful way to test 'em with less than three test leads and out of the
circuit. Curve tracer can help there...assuming you can even determine
which lead is which element of the FET.

My TV quit, no sweep. Turns out that virtually every circuit in the thing
had some kind of interlock with the sweep, so nothing was running.
Was a fet in the horizontal oscillator. Tested the thing in circuit
until I was blue in the face. Finally ran out of options, gave up and
pulled it out.
A tiny bug had committed suicide between the leads. Bug Juice has some
interesting nonlinear properties. Didn't conduct enough to see at low
voltages, but at higher voltages, the pins were shorted. Not sure a
curve tracer would have helped in-circuit.

A friend came over once with some RF power transistors out of his 450
MHz. transmitter. They all looked the same on the curve tracer at
normal working
currents. A better indicator of a bad transistor turned out to be some
small Collector-Emitter leakage that you could read on an ohm-meter.

Bottom line is that there's no easy answer.

 

[slampen]

Den 01.01.2011 20:27, skrev JeffM:

[...]transistor tester module available which can connect to a XY scope
or a computer and give me the 'graphs'[...]

http://octopus.freeyellow.com/octopus.html

Any comment on this tester? Adequate in an hobbyist's shack...?

http://www.circuit-ed.com/CT100.htm

Geir

 

[Jon Kirwan]

Den 01.01.2011 20:27, skrev JeffM:

[...]transistor tester module available which can connect to a XY scope
or a computer and give me the 'graphs'[...]

http://octopus.freeyellow.com/octopus.html

Any comment on this tester? Adequate in an hobbyist's shack...?

http://www.circuit-ed.com/CT100.htm

I couldn't get the page to load. I then found the following
comments dated Nov. 25, 2010:

"Except that they stopped making it about a year ago
and show no sign of manufacturing anymore. I've emailed
them about it and requested a response on the DIYAudio
forum, but it seems to be a no go! On the DIYAudio
forum someone told me about the Elektor 'project' and
it seemed quite attractive until I received a whole
bunch of reports from people who said that they had
problems with it."

The page that included the above comment also had this link,
which does load:

http://www.elektor.com/magazines/2009/february/transistor-curve-tracer.810360.lynkx?tab=1

I'm not sure what to make of these things, but there it is.

I have a small circuit I built decades ago that I built into
a 35mm plastic film container (with a BJT socket mounted)
that had two LEDs, one red and one green. No micro, just a
simple oscillator and a few parts. I'd put the BJT into the
socket and if it is NPN the red LED lights, if it is PNP the
green LED lights, and if it doesn't work for some reason then
neither or both will light up. Never failed me. But it
doesn't do curve tracing or tell you any quantitative things
-- just go/no go for the device and what type it is. I could
provide the schematic, if that's what you'd like.

Jon

 

[Baron]

Jim Yanik Inscribed thus:

Den 01.01.2011 20:27, skrev JeffM:

slampen wrote:
[...]transistor tester module available which can connect to a
[XY
scope or a computer and give me the 'graphs'[...]

http://octopus.freeyellow.com/octopus.html

Anyone knowing how a curve tracers curves should look like for a
Power N-FET transistor??

regards Geir

There are better curve-trace adapter designs out there... IF you
really are intent on doing serious testing.

...Jim Thompson

if you can find a Tektronix 7CT1N,7B53A,and 7000 series
mainframe,you'll have a nice small-signal device curve tracer,up to
300 Vcc.I had one on my bench at Tek.
There's also the 5CT1N and 5000 series Tek mainframe,but the 5K stuff
was el-cheapo compared to the 7K.

I've got an old 7000 mainframe in the garage, no plugins though. It
must have been in there for at least ten years or more. Bet it goes
bang when I plug it in...

 

[Baron]

Jon Kirwan Inscribed thus:

Den 01.01.2011 20:27, skrev JeffM:

slampen wrote:
[...]transistor tester module available which can connect to a XY
[scope
or a computer and give me the 'graphs'[...]

http://octopus.freeyellow.com/octopus.html

Any comment on this tester? Adequate in an hobbyist's shack...?

http://www.circuit-ed.com/CT100.htm

I couldn't get the page to load. I then found the following
comments dated Nov. 25, 2010:

"Except that they stopped making it about a year ago
and show no sign of manufacturing anymore. I've emailed
them about it and requested a response on the DIYAudio
forum, but it seems to be a no go! On the DIYAudio
forum someone told me about the Elektor 'project' and
it seemed quite attractive until I received a whole
bunch of reports from people who said that they had
problems with it."

The page that included the above comment also had this link,
which does load:

http://www.elektor.com/magazines/2009/february/transistor-curve-tracer.810360.lynkx?tab=1

I'm not sure what to make of these things, but there it is.

I have a small circuit I built decades ago that I built into
a 35mm plastic film container (with a BJT socket mounted)
that had two LEDs, one red and one green. No micro, just a
simple oscillator and a few parts. I'd put the BJT into the
socket and if it is NPN the red LED lights, if it is PNP the
green LED lights, and if it doesn't work for some reason then
neither or both will light up. Never failed me. But it
doesn't do curve tracing or tell you any quantitative things
-- just go/no go for the device and what type it is. I could
provide the schematic, if that's what you'd like.

Jon

That sounds like it should be a toolbox item !

 

[Jon Kirwan]

Jon Kirwan Inscribed thus:


That sounds like it should be a toolbox item !

I found something similar to it on the web. It's on this PDF
file's page 3:

http://www.edn.com/contents/images/122001di.pdf

Jon