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Old 23rd Mar 2018, 5:59 am   #1
ziggy2000
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Default X-Y/Lissajou mode on Telequipment D54?

Hello, forum newbie here from across the pond. On a whim I recently picked up a bargain Telequipment D54. I have been trying to discover if it is possible to employ the x-y mode for this vintage scope. There is no explicit XY button or place on the timebase knob, but there is a position for "EXT X". Unfortunately I can't figure out how to use it!

The manual says "The EXT X setting enables an external signal to be applied between the EXT X and GND terminals to provide horizontal deflection of the beam." Additionally, "EXT X provides d.c.-coupled access to the input of the horizontal amplifier. This facility is of use with Lissajous and swept-frequency techniques." But there is no explanation of how to connect the signals to achieve the desired effect. Since Lissajous is the primary usage I envision, I would like to know how to connect the signals correctly. I include a picture of the timebase section of the front, with connection terminals. If anyone can help with instructions on how to connect, I would be greatly appreciative.

If more information is needed I will be happy to provide. Thanks!
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Old 23rd Mar 2018, 9:56 am   #2
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Default Re: X-Y/Lissajou mode on Telequipment D54?

To get the classic lissajou display, apply one sine signal to the Y-input as normal and another sine signal to the Ext X input. It should work straight away. Get the required patterns by adjusting the two frequencies.
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Old 23rd Mar 2018, 2:00 pm   #3
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Default Re: X-Y/Lissajou mode on Telequipment D54?

Welcome to the forum, you wouldn't be making Mr Carlson's component tester/ curve tracer by any chance?

Some scopes have a dedicated position on the Y axis/time div knob for XY mode, it looks like your D54 does. Try setting knob in alignment with the X "line" and see if that does the trick. Others you have to play with the time/div knob to get the best trace.

Andy.
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Old 23rd Mar 2018, 10:19 pm   #4
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Default Re: X-Y/Lissajou mode on Telequipment D54?

I don't have manual to hand, but I would guess about 1v per div sensitivity. Just feed in that 1v pp cal signal in to Ext in with TB set to that position and see what happens. The same signal fed to the Ch 1 input (set to 1v/div)should give a stationary figure on the screen with same vert and hor deflection IF it is 1v/div of Ext.
With many scopes, the X signal is connected to Ch 2 with switches set as appropriate.
The bandwidth of the X amp is probably 1Mhz compared with the 10MHz of the Y amp. Expect distortion with signals approaching 1MHz frequency.
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Old 24th Mar 2018, 3:49 am   #5
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Default Re: X-Y/Lissajou mode on Telequipment D54?

Quote:
Originally Posted by Andrew2 View Post
To get the classic lissajou display, apply one sine signal to the Y-input as normal and another sine signal to the Ext X input. It should work straight away. Get the required patterns by adjusting the two frequencies.
Thanks for the replies from all! Funny thing I'd, tried the hookup provided by Andrew above and thought it didn't work. I was trying to do it from the headphone output of a smartphone with a signal generator app. I noticed a very small deviation in the X when I applied the signal to the EXT X terminal. I figure there was just not enough voltage from the small device to drive the x-sweep. Coming out of the output from a desktop soundcard was much better, I was able to get some classic lissajous forms. Looks like this old scope has no way to vary the voltage on the EXT X setting as you can on the normal inputs. Adjusting the sound card volume and playing with the gain control got me an acceptable display.

The other anomaly is that the "normal" XY slope from applying identical signals was reversed - instead of bottom left to top right it was top left to bottom right, like a 180 degree phase difference. Not sure why that is occurring, but not really a huge problem. I can still use it to generate some impressive graphics. I will not complain getting a fully functional scope for about 25 USD!

Cheers!
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Old 24th Mar 2018, 5:10 am   #6
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Default Re: X-Y/Lissajou mode on Telequipment D54?

From time axis div. knob on my D-54, go anti-clockwise all the way to bottom left, a line points to X input below.
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Old 24th Mar 2018, 3:25 pm   #7
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Default Re: X-Y/Lissajou mode on Telequipment D54?

Quote:
Originally Posted by Diabolical Artificer View Post
Some scopes have a dedicated position on the Y axis/time div knob for XY mode, it looks like your D54 does. Try setting knob in alignment with the X "line" and see if that does the trick. Others you have to play with the time/div knob to get the best trace.
Andy, I think you are getting confused and thereby possibly confusing the OP. The "time/div" knob is for the X-axis (horizontal), not the Y-axis (vertical). Also, if by "play with the time/div knob" you mean "set it to external X", then I agree, but any other setting would just send the time-base sweep to the X-axis, wouldn't it? Or am I getting confused??

It has to be said, though, that Lissajous figures are, though sometimes pretty, of limited use...

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Old 24th Mar 2018, 5:26 pm   #8
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Default Re: X-Y/Lissajou mode on Telequipment D54?

Quote:
Originally Posted by ColinTheAmpMan1 View Post
It has to be said, though, that Lissajous figures are, though sometimes pretty, of limited use...
They were demonstrated to us at college when we were being shown how to use a scope for TV faultfinding but only to gain our interest. Someone had asked him what the X input was for and initially he said, 'It's for when engineers get bored and have no work to do.....they can make patterns on the screen....'! He then proceeded to show us the classic patterns produced by two audio generators when fed into the X and Y inputs. I suppose for about 15 minutes we all had a go at producing some patterns but then the novelty wore off. He then showed us what the X input was really for....using a wobbulator to show the the alignment curves.

To this day, I have never found a practical use for lissajous patterns. I suppose they may have some merit when checking phase errors in audio amplifiers?
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Old 24th Mar 2018, 9:02 pm   #9
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Default Re: X-Y/Lissajou mode on Telequipment D54?

We used lissajous figs in Physics at tech, but I had already seen them in use at work. One of our SOs was trying to develop a non destructive method of assessing strength of salt glazed drainage pipes. A fairly good relationship between ultimate strength and Young's modulus had been established, so this was determination of YM by finding standing wave nodes using LF oscillator and transducer for input, and a record player stylus and cartridge to find the nodes.
Later at tech, the same sort of measurements, so I already understood it. LONG time ago!
Ziggy, have you tried the cal signal as I suggested for simple testing. You do have a cal variable by using the red "X gain" control. Easy to input a 1v DC at X input and choose a suitable position of X gain, ergo, calibrated X deflection. But it is very limited compared with Y-input gains.
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Old 24th Mar 2018, 11:06 pm   #10
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Default Re: X-Y/Lissajou mode on Telequipment D54?

I have't tried it yet, but what a about a certain value pot in the EXT. X input of the D-54, would this not give you a better and quicker method and control of the signal amplitude or signal?
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Old 25th Mar 2018, 7:35 am   #11
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Default Re: X-Y/Lissajou mode on Telequipment D54?

Quote:
Originally Posted by Sideband View Post
To this day, I have never found a practical use for lissajous patterns. I suppose they may have some merit when checking phase errors in audio amplifiers?
Yes, they're handy for comparing the phase of two signals. They're also useful for comparing, very precisely, two signals which are close in frequency, for example aligning a crystal oscillator to a frequency standard. The closer together the signals are, the more slowly the lissajous pattern will move. Very tiny differences are easy to detect this way.

Chris
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Old 25th Mar 2018, 8:03 am   #12
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Default Re: X-Y/Lissajou mode on Telequipment D54?

Doh! Your right Colin, well caught, got me X and Y mixed up.

Have a look at this - https://www.youtube.com/watch?v=YqSvkNjWnnQ he takes it to another level.

The X/Y function can be useful for quick fault finding EG by comparing the two channels on an amp, one channel good, tother bad by used with an Octopus, see here - http://www.solorb.com/elect/testcirc...us1/index.html and for testing zeners etc. there are better one's like the one Mr Carlson made on his patreon channel.

Andy.
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Old 25th Mar 2018, 8:06 am   #13
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Default Re: X-Y/Lissajou mode on Telequipment D54?

Handy for calibrating the scale on a home-made audio oscillator, using mains as the reference.

used for trimming the frequency of quartz watches.

David
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Old 25th Mar 2018, 4:26 pm   #14
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Default Re: X-Y/Lissajou mode on Telequipment D54?

Quote:
Originally Posted by MotorBikeLes View Post
Ziggy, have you tried the cal signal as I suggested for simple testing. You do have a cal variable by using the red "X gain" control. Easy to input a 1v DC at X input and choose a suitable position of X gain, ergo, calibrated X deflection. But it is very limited compared with Y-input gains.
Hi Les! I applied the CAL signal, which is called out as 500mVpp next to the connector, to the EXT X input. Even at the highest gain there is only a small deflection, about the width of one square on the grid scale. See my picture.

Again, I am working with the relatively low output of a PC soundcard. With a proper signal generator I'm sure I could make prettier pictures.
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Old 25th Mar 2018, 6:48 pm   #15
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Default Re: X-Y/Lissajou mode on Telequipment D54?

That sounds about right. The spec for X includes the following for volts per cm.

Horizontal amplifier
Deflection sensitivity approx. 600mV to 3V/cm
Maximum input 400Vp
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