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Old 17th April 2010, 11:40 AM   #21
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It does take practice especially ensuring initial settings are correct for the particular DUT
I found that I had better success after a 2nd and 3rd through re-reading of the manaul......it is agreat reference (best I've found)

See Manual pgs 56-59 and 62 (HK pg numbers)

Running through all the steps on tracer & OS setup 58-59 is the key.

Is looping across entire horizontal portion of curve without traces crossing? Like 1st picture.
.........loop trimmer is to be adjusted with vertical sensitivity temp set at .5mA/div then vertical sensitivity returned to previous setting.......trimmer is not used as a adjustment other than at this stage of setup.....

Or is looping like any shown in 2nd picture? The loop itself is indicative of certain conditions pg 62

If family of curves show looping like in pic3 with a curve crossover at end, its easy to see current change due to heating (lower test V, sink it,etc) Realize the curves don't 'terminate' (open ended)....they have a return path ie 'trace'.

Pic4 ...a curve rolling 'up' towards vertical as it 'returns' is definitive for thermal runaway. you've probably ruined it with too much current.

Charles
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I'm kinda curious about that myself........
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Old 17th April 2010, 01:34 PM   #22
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I will post a couple of pictures later on to show exactly what I get.
I think I am on the first situation.
One thing though: On calibration position I can't get the dots on each beginning of graticule. I mean it is not exactly spot on.
I tried to adjust the sensitivity of the oscilloscope but it is hard to get them all on the right place.
I will post this pic too...it might be normal...hopefully.
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Old 7th October 2010, 05:21 AM   #23
locky_z is offline locky_z  China
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this link 'DIY Curve Tracer for PC'
DIY Curve Tracer for PC
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Old 7th October 2010, 06:14 AM   #24
richiem is offline richiem  United States
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A Tek 7000 series scope and a 7CT1N will set you back a *lot* more than you have indicated you want to spend -- recently as much as $700 on fleabay. Also, the 7CT1N does not do high current, but does do relatively high voltage -- peak around 250-300V. Leader made a very nice outboard unit, the LTC-905, that uses X-Y inputs on a scope for display, but it is limited to 100V and 100mA, as is the similar B&K unit, an 800-something if I remember right.

There are no inexpensive 1A capable units that I know of. One could be built or modified for higher current by using a bigger transformer and smaller current limiting resistor.

You can download a Tek 7CT1N or 5CT1N manual for free I think, from Tek's website or from the BAMA site, and look at how it's done -- those units are about as simple as such things get when you need enough precision to match devices. Of course an ordinary component tester built from a filament transformer and some resistors and connected to an X-Y scope, will give you quick good/bad testing.
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Old 7th October 2010, 06:21 AM   #25
richiem is offline richiem  United States
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The trace looping is because the test frequency -- 60Hz -- interacts with the reactive components, including the transformer and stray capacitance, and cause hysteresis and impedance vs level shifts. It's normal -- you just live with it.
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Old 7th October 2010, 01:20 PM   #26
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There's a loop compensation adjustment on the TEK 576.

Interesting that a 576 will cost less than a 7CT1N. Nevertheless, I wouldn't buy a 576 without first seeing it with my own eyes, and playing with or, or purchasing from an absolutely reliable seller -- this a case where "doubting Thomas" will save you money.
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Old 26th November 2010, 11:09 PM   #27
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One of the Yahoo TEK Scopes guys has built a "virtual" 5CT1N using audiotester.de --- neat--OH!

http://groups.yahoo.com/group/TekSco...96326/pic/list
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Old 21st May 2011, 09:39 AM   #28
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Does anyone happends to have a manual for the Heathkit It-1121 or It-3121 curve tracer?
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Old 22nd May 2011, 05:17 PM   #29
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I should hve it somewhere.

being honest though, the curve tracer is not that great and I don't see any specific use for precise matching of Jfets and or mosfets.

I want to leave the benefit of the doubt that I am not using it properly.


If you have the curve tracer, have you had any success using it?
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Old 23rd May 2011, 10:39 AM   #30
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Quote:
Originally Posted by Stefanoo View Post
I should hve it somewhere.

being honest though, the curve tracer is not that great and I don't see any specific use for precise matching of Jfets and or mosfets.

I want to leave the benefit of the doubt that I am not using it properly.

If you have the curve tracer, have you had any success using it?
Yes, that's the information I have found also since posting.
No, I don't have the heathkit curve tracer.

Currently I am thinking of buying and restoring a TEK 577 curve tracer instead. I have seen that Chinese companys makes "lower cost" curve tracers, but are they reliable or any good?

I think I will go for a TEK. Anything in particular to think about when
buying one? What about the life of the CRT?
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