ETI Curve Tracer Project

[Yorkie]

While rummaging about in the loft, I've found a box marked 'curve tracer project' and on opening it I found a completed PCB and all the other parts needed to make a simple transistor curve tracer which featured in the long since defunct Electronics Today International 'Electronics Digest' in Autumn 1980. I was horrified to note the date when I'd made the PCB - 1982 - 33 years ago! I have only the vaguest memory of having made the board and gathered together all of the other bits. Lots of my homebrew projects have a longish gestation period before they come to fruition, but this one really is the giddy limit.

I thought I might try to finish it, but note that the article states: "The design allows the dynamic voltage-current characteristics of diodes and transistors to be displayed on the screen of a DC scope capable of taking an external 'X' input". I have a Hameg 203-7 dual trace scope, which has a socket to allow external triggering. Excuse my ignorance, but would that be the 'external X input?' Apart from the two 'Y' input sockets, that's the only other one.

No point in finishing the project off if it won't work with my 'scope - assuming that it does indeed work when finished!

Any thoughts anyone please?

(Unfortunately the article is a faded photocopy, and though legible, won't scan sufficiently well to add it to the thread).

[ppppenguin]

External X is not the same as external trigger. On many dual trace scopes you can use one Y channel for Y and the other for X . On many Tektronix scopes this is done by turning the timebase speed to a special position to the left of the lowest speed. I don't know about others.

[Mark Hennessy]

I have a Hameg 203-7 dual trace scope, which has a socket to allow external triggering. Excuse my ignorance, but would that be the 'external X input?' Apart from the two 'Y' input sockets, that's the only other one.

That's what the "X-Y" button is for.

Press that button and Channel II becomes the X input.

Some 'scopes allow the external trigger input to become an X input, but I'm not sure that's the case with your Hameg. But in any case, X-Y mode is better because you have full control over the gain of that input.

[Yorkie]

Thanks for your prompt and helpful responses, Terry & Mark.

Yes, I've found the X-Y button - never noticed it before as I've never had cause to use it.

The older I get, the less I seem to know!

No excuses now for not finishing off this little project, which I started when 'Dexy's Midnight Runners'  were #1 in the charts with 'Come on Eileen'.

[AlanBeckett]

You'll be advancing to a real 'scope one of these days young David

A couple of weeks ago I was playing with one of my 7000 Series Tek 'scopes and I had to consult the Timebase Manual, 7B53A - can't remember what for. Bear in mind that I've been using these since about 1975. While at it I noticed that if you pulled the 'Delayed' Knob you got a Mixed Sweep. I swear that in 40 years I've never used that Function. Actually I regard it as pretty useless. Some of the old Valve 'scopes like 545 and 547 did Alternate as well although I've never rated that either.

So, after 40 years of being confident that I knew everything about them I've discovered something new. Of course I might have just forgotten, but .......

Alan

[Keithstv]

One company I worked for back in the 70s had a 7000 series scope with 4 plug in slots. with two dual timebase modules and two dual channel Y amps I had 16 traces on the screen. However it was virtually impossible to make any meaningful measurements due to the small screen size.

This thread has reminded me that for next years Golborne talk I'll need to put together a curve tracer to display valve characteristics which will be based on a similar principles to this transistor curve tracer.

Keith

[Terry]

Thanks for your prompt and helpful responses, Terry & Mark.

David, it was Jeffrey & Mark, actually! I was going to respond but Jeffrey beat me to it!

[Yorkie]

Thanks for your prompt and helpful responses, Terry & Mark.

David, it was Jeffrey & Mark, actually! I was going to respond but Jeffrey beat me to it!

Ooops - thanks for your good intentions anyway Terry, and to Jeffrey for his advice.

[radioman]

This circuit was originally in the December 1978 issue of ETI.
I could scan it from the magazine and post it here if you'd like.

Andy

[Yorkie]

That would be great Andy - for me at any rate, as I only have a faded photocopy from the Autumn ETI 'Digest'.

I did tidy up the PCB artwork, which is attached should anyone wish to build the project when Andy scans and posts the article. (The PCB is 8cms square).