Curve Tracer

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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 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.
 
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.
 
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.
 
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?
 
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?
 
As I said a few posts back, don't purchase a curve tracer without either 1) playing with it yourself to make sure it works, or 2) purchasing from a dealer with a decent return policy. You might want to query the TekScopes Yahoo group for more advice. You can search the message archive for info.

The 576 is capable of higher currents than the 577.
 
I bought a Tek 576 off Ebay a few years ago and modded it for tube testing.

The main problems I had were the rotary switches being flaky. These operate via cam rollers that depress spring contacts onto gold plated PCB foils. The higher current contacts had burned small holes thru the foils. Particularly the ones operating the readout bulbs, but there are others too.

I was able to fix this by some very delicate surgery. Either heat up the solder holding the springs to move them slightly with tweezers or bend them slightly. Tricky to say the least. But patience paid off. These cam switches are also very susceptible to dust getting in them and causing opens. The contacts don't slide.

The other issue would be to check the CRT for burn spots around the lower left 0/0 corner. And check for cracked knobs.

One nice thing about the 576 is it has an internal hidden option for external Vertical or Horizontal signal inputs. Was used by one of the upgrade DUT plug-ins. I just wired the inputs to some BNC connectors. Now I can monitor tube screen grid current or Mu easily with some external current or V probes.
 
Hi Peeps,

Just a quick support for the comment about the Curve Tracer (advanced).
I produced one based on this, and added MOSFET mode as well, I originally built it to characterize some FETs for an audo oscillator.
If I ever see the CT for my 7k mainframe at the right price I will probably grab it as well, and a 7L5 :eek:)

Cheers

Paul
 
One nice thing about the 576 is it has an internal hidden option for external Vertical or Horizontal signal inputs. Was used by one of the upgrade DUT plug-ins. I just wired the inputs to some BNC connectors. Now I can monitor tube screen grid current or Mu easily with some external current or V probes.

PLS grid current - how most sensitivity range your modded CT have ?
 
"PLS grid current - how most sensitivity range your modded CT have ?"

The external inputs (using the 10X magnifiers on) on the 576 appear to have 2.5 mV/div Vertical sensitivity and 5 mV/div Horiz. sensitivity. I use a Tek AM503/A6302 DC current probe unit with it to sense currents, which has 1 mA/10 mV out lowest range (using a 50 Ohm cable terminator, but can get about 2x sens. without the terminator, not Cal'd then). So should give .25 mA/div Vertical (with terminator) or about .125 mA/div Vertical (no terminator). There is significant noise in the signal at such high sensitivity though (5 MHz or 50 MHz BW available on the AM503) , but a low pass filter (RC) will fix that for Curve Tracer use.
 
Hi Sendy,

The brief spec is as follows

Collector current limit 7 to 80 mA adjustable
Collector voltage 20 to 80 in 4 steps
Base current steps 2 uA to 1mA in ranges
Gate drive steps 0.1V, 0.5V, 1.0V

Modes BJT, JFET, MOSFET, Nor P polarity

Xoutput 100mV/V . Youtput 0.1V/mA

It fun to drive, but I am still looking for a 7CT1N :eek:)

Cheers

Paul
 
The 576 is capable of higher currents than the 577.

The 576 and 577 both go to 20 amps. The difference is the 576 collector supply is 15V at 20 amps, the 577 is 6.5V at 20 amps. The 176 Pulsed High Current plugin "front porch", which only works on the 576, can do 200 amps at 15V, 40 amps at 75V, or 8amps at 300V. There was a high current option for the 575. It was a big transformer that sat on the floor and weighed maybe 100 pounds. The 577 had a plugin that tested op-amps. But nobody here uses op-amps, right?
 
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Joined 2011
Is Surplus Curve Tracers Still Worth Buying?

I don't want to start yet another thread on curve tracers, so I will just piggyback onto this one, since the discussion is relevant still. Since none of the older curve tracers can be interfaced with the PC, and are bulky, heavy and full of obsolete parts, why get one?! With that said, I still want one:headbash:, can some one talk me out of it!:D

Jaz
 
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