Telequipment Oscilloscope D75

Thread Starter

odoardo

Joined Apr 19, 2008
8
I have an O'scope Telequipment D75 with Dual Trace Amplifier V4 and Dual Sweep S2A boxes.
http://www.grix.it/UserFiles/odoardo/Image/Immagini/Teleq-D75.jpg
Do someone know this equipment?
I need to use it in X-Y mode as a curve tracer but, this equipment only has External X mode.
I would want to try a circuit to produce this function (in case it is not very complicated built in), I've all the schematics of oscilloscope D75 that I can post in case someone can help me.
Thanks to all
Odoardo
 

SgtWookie

Joined Jul 17, 2007
22,201
Well, have you tried selecting External X, using channel 2 as your X input, and channel 1 as your Y input?

That should do it for you.
 

Thread Starter

odoardo

Joined Apr 19, 2008
8
Yes I already tryed but doesn't work.
Only run selecting EXT X, using channel 1 (or ch 2 is the same) as Y input and the right input in the S2A as the X input, but is not possible to settle any range with Volt/Div (the X axis should be the voltage of the curve tracer).
With another oscilloscope with X-Y mode all the circuit works very fine.
Odoardo
 

JoeJester

Joined Apr 26, 2005
4,077
Take a pic of how you have the knobs positioned for X-Y ... because your photo doesn't have the time base all the way to the maximum ... X
 

SgtWookie

Joined Jul 17, 2007
22,201
Like JoeJester says, set your timebase knob all the way around to where it's lined up with Ext X, and push the Ext button above your Ch. 2 input. Then whatever voltage is on the Ch 2 input will cause the trace to move horizontally.

Ch 1 moves the trace vertically.
 

Thread Starter

odoardo

Joined Apr 19, 2008
8
I add 2 more images to explain better my need.
On the oscilloscope (Unaohm) with X-Y mode I can select the appropriate range of voltage on X axis (1V range in this case) and current in Y axis (in this case 10mA corresponding to 1V range).
In the present oscilloscope (Telequipment) with EXT X, I can select only the current on Y axis, no chance to select the Voltage of X axis (as can see the characteristics go outside the screen).
I'm obliged to use Telequipment Scope but I need to select also the X axis range.
http://www.grix.it/UserFiles/odoardo/Image/Immagini/telequipment.jpg
http://www.grix.it/UserFiles/odoardo/Image/Immagini/unaohm.JPG
 

SgtWookie

Joined Jul 17, 2007
22,201
Looks like you need to use a pad on the external X input.

You might try using a broadband opamp with an adjustable gain feedback. Make sure you match impedances; 50 Ohms in, 50 Ohms out.

You'll probably have to compensate using a trimmer capacitor, somewhere in the range of 5pF to 60 pF.
 

Thread Starter

odoardo

Joined Apr 19, 2008
8
Thank to SgtWookie,
I undersand that using an opamp is possible to arrange the right voltage range for external X input, but is not the same think as the X-Y mode.
You think it's too hard to make circuit modification of the Oscilloscope D75 to arrange the real X-Y Mode?
Do you have some circuit idea to try?
Odoardo
 

JoeJester

Joined Apr 26, 2005
4,077
It looks like on one scope ... your using x1 probes and the other your using x10 probes.

Another possibility is you moved the vernier dial out of the locked position on the Y channel.

Check your setup.
 
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