Test Equipment Question

[dangjalopy]

I recently acquired a Sprague Transistor Curve Tracer by Jud Williams! I am trying to rig it up to connect to my O-scope. There is a 3-pin DIN (female) panel connector on the front. I am thinking this is the only way to connect to an outside monitor. I do not have a schematic and have not found any info on this tracer on the net. Anybody have any info on this tracer? I would like to know if I can rig up a DIN to BNC cable that will let me view the traces on the O-scope. the pinout info i found was kinda vague so any info you may is much appreciated. thanks in advance!

Travis

[Robert Reed]

If the tracer is complete in itself, I would think the 3 pin DIN connector would be supplying X axis, Y axis and ground for the scope. Can you power it up with a transistor installed and probe each connection with your scope to verify? If successfull either rewire the DIN connector with BNC connectors or get the mating end and attach BNCs with cables to that.

[Bob Scott]

This thing?



It says "PROBE". It has 3 pins, like you said. I would think it is there to connect to the EBC contacts of the transistor and possibly a shield too at the DIN shell contact.

By the way, this photo will probably disappear in 4 days and 22 hrs. It is referenced from ebay. They have a couple of Heathkit curve tracers, and also a couple of B&K "Precision" units for sale.

Bob

[dangjalopy]

thats exactly what i have except my DIN doesn't say PROBE. that clears a lot up. thanks! any idea how to find a probe like that? what to look for? or should i make my own? thanks!

[Bob Scott]

thats exactly what i have except my DIN doesn't say PROBE. that clears a lot up. thanks! any idea how to find a probe like that? what to look for? or should i make my own? thanks!

You probably won't find one, so make one. I suspect that the din socket is wired like a TO-5 transistor socket. As you look at the front panel.

Left contact: Emitter
Middle (lower) contact: Base
Right contact: Collector

That is just a GUESS. If that is not right, no harm done. Just experiment with low current and voltage with different probe pin positions on a transistor until the curve tracer output looks like a transistor curve.
Some bipolar transistors may work to some extent when E and C swapped. Then swap E and C. Which waveform looks best?

[haklesup]

It's not a socket for a probe per se, its intended to plug the transistor directly into it. This type of transistor socket was common even on the Tektronics 576 (and similar) curve tracers though it would have been nice if the manufacturer also put banana jacks on it as well. in fact you might just want to do exactly that once you definitively figure out the terminals. This is intended for mainly TO-92 or similar packages.

[dangjalopy]

thanks a lot guys. It has banana "plugs" but not jacks on the back. I was thinking maybe that was how it is connected to the o-scope. not sure. may have to do some reverse engineering to figure this thing out. thanks!

[Bob Scott]

It's not a socket for a probe per se, its intended to plug the transistor directly into it.

So that label that says "PROBE" isn't really there per se?
I see a standard 3 pin DIN jack with a shield contact, not a transistor socket.

Bob

[haklesup]

So that label that says "PROBE" isn't really there per se?

I guess I lost that in the glare, I see it as I zoom in now

What do you think of the selector switch? I can't quite make out the word in the middle. What is on the "Left"

I would think the banana plugs are to interface to a scope but I would think that a BNC would be more universal.

[Dean Huster]

Assuming it to be the probe connector for the device under test, you can use a scope to figure it out. One pin is likely ground -- an ohmmeter between it and chassis likely will show zero ohms, assuming the unit doesn't use floating supplies. Another pin will show a stairstep waveform and this is the base connection. The last pin should have a ramp on it and will be the collector connection. If you have a dual-trace scope and look at the ramp and step simultaneously, you should see one ramp for every step.

The Tektronix 575, 576 and 577 curve tracers used banana jacks for their main connections and you bought a series of very pricey adaptors for the various transistor packages you wanted to use. The Tek 576 and 577 used Kelvin connections for the collector and emitter so that accurate voltage measurements could be made, considering that up to ten amps could be measured. The really sweet instrument to have is the Tektronix 570 vacuum tube curve tracer (vs. semiconductor curve tracer). I have built an adaptor for a 576 allowing it to do curves on a 12AT7 dual triode and similar vacuum tubes -- one of those, "I wonder if I can make a ..." design project that's really rewarding when it works.

[Bob Scott]

.......The really sweet instrument to have is the Tektronix 570 vacuum tube curve tracer (vs. semiconductor curve tracer). I have built an adaptor for a 576 allowing it to do curves on a 12AT7 dual triode and similar vacuum tubes -- one of those, "I wonder if I can make a ..." design project that's really rewarding when it works.

12AT7 ? Isn't that one the most linear of the 12AT7/12AU7/12AX7 series? Time for a new thread!

Bob

[dangjalopy]

Dean,

Since you seem to be able to afford one of those Tek's, how about buying me one?!?! haha! If I could afford one, I would gobble that thing up. thanks!

Travis

[Dean Huster]

Sorry, Travis. I have a 575 (an old 500-series vacuum-tube version) semiconductor curve tracer and a 7CT1N for my 7904, but no 576 or 577. I've had intimate access to a 576 over most of my electronics career, so had gotten really spoiled when I didn't have one. My 575 has been in storage for a long time, so I'm sure has myriads of bad electrolytic caps in it now and will probably explode if I try to turn it on.

[dangjalopy]

haha! thanks dean. Im going to play with it today since i have the day off. hopefully i can find a way to make it work. I may have to install a 5p DIN to make it work and just use 3 pins. I have had no luck finding a 3p DIN to use as test leads.