Blanking the retrace - Analog scope

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atferrari
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Blanking the retrace - Analog scope

Post by atferrari » Sun Jul 19, 2009 6:44 am

I managed to show on my scope a symbol formed by several dots by controlling voltages at the X-Y axis.

To make it neat I would need to blank the retrace between dots.

My scope is an old analog TRIO 10 MHz CS1562A. Couldn't find the manual but a PDF version found in the Web says that "modulation" may be done "at TTL" levels.

Just in case, I tried myself bringing the Z axis input to 0V and 5V, getting only a change in brightness.

Is it any way I could blank completely the retrace in between spots?

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Re: Blanking the retrace - Analog scope

Post by Robert Reed » Sun Jul 19, 2009 7:42 am

I have only tried "Z" axis blanking on several scopes that I have owned. But if memory serves me correctly, these all required a negative voltage into the Z axis input. Were your inputs pos. or neg. The 5 volt span sounds about right for total cutoff of the electron gun, but from my 'dabbling', it required a 0 to -5 volt signal.

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atferrari
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Re: Blanking the retrace - Analog scope

Post by atferrari » Sun Jul 19, 2009 7:55 am

Hola Robert,

Since it says TTL levels I dared to apply 0V and +5V.

Just five minutes ago found the manual: between the Z input and the control grid there are lot of transistors. The whole is closely linked with the Intensity panel control.

Would you say that the input transistor would not complain if I apply -5V to the input?

I am affraid to ruin the only scope I have.

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atferrari
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Problem solved - Thanks Robert

Post by atferrari » Sun Jul 19, 2009 8:13 am

I followed your comment: -5V did the trick.

Muchas gracias. :grin:

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Bob Scott
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Re: Blanking the retrace - Analog scope

Post by Bob Scott » Sun Jul 19, 2009 1:30 pm

I once had a bit of extra time at work and did a little experimenting. I wanted to display a TV picture on the 2 channel Tek scope. I set the scope to X-Y mode, got one channel to trigger on H sync, the other to trigger on V sync, and connected the Z axis to composite video.

It did display a stable TV picture, but as a negative image in black-and-green. I guess the Z axis on that particular Tek scope got brighter with a negative voltage, the reverse of what I expected. The experiment did show that the Z axis responds linearly to an analog signal.
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