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?

 

You may have the brightness set too high for the Z-axis input to completely blank the trace. It's also possible that there are problems with the Z-axis input circuitry.

 

Everything seems to work well in normal use. To control the brightness, the Intensity controll was enough since I bought it more than 30 y ago. Mybe it is because I am trying to do something that the scope was not built for...

 

A PDF version of the manual is here: http://www.casa.co.nz/Equipment/Scope/Trio-CS1562A-Man-A3-16p.pdf
(that may be the same version you found)
On page 8 of 16, it says:

26. Z AXIS INPUT Jack
Intensity modulation jack. TTL logic-compatible.
High logic increase brightness, low logic decrease brightness.

There is also a schematic of the O-scope which I haven't spent much time reviewing, but it appears that the Z-axis input (at bottom center of schematic) would by default be held at a logic low level (0v). So, if you turn the brightness down, that should take care of the blanking issue.

 

Were you not able to find the z-axis input to your scope as sgtwookie suggested? If present, it is typically located on the rear of the instrument.

hgmjr

 

If you are operating in X-Y mode, there is really no retrace interval. The magic may be arranging for the portion of the signal you don't wish to show to have a level that makes it invisible. 0 volts ought to be that level, so your o'scope may be a bit out of adjustment.

 

First of all: thanks to you all for replying.

Using -5V at the Z input, did the trick. Now back to some judicious programming.

Just a word: I used the wrong word because I know that retrace is specific when I use the triggered modality. I just tried to name the trail visible when the beam goes from one spot to the next.

Happy to have something solved.

Gracias to you all again.

 

After persisting in my idea, I managed to get the blanking done.

The transistor involved, a 2N2222 and later a TCG229 (VHF) did not switch with a 1.8 usec (560 KHz) pulse. !!??

By software I increased it to 10 usec ON - 10 usec OFF and it works. Trails are properly blanked now.

The problem is when I try to show the maximum possible number of characters on the screen I will need a much faster routine thus a shorter pulse for blanking. How to get it?

Circuit in use, shown in the attachment. Ideas anyone?