Calibrating a Cadet IV Ramp Generator

Could anyone shed some light on how to set up the ramp generator.
If i set the trim pots so that the V /| and H /| outputs are centred on screen, i cannot see anything from the H |\ and V |\ outputs.
If i use the H \ / and V \ / outputs, i can just about get the centre to the RHS of the screen but there’s no more give on the trim pot.

Is there any documentation for calibrating this or is there a mistake in my build?


Here’s the method I’ve used. This is a copy and paste from a previous message I sent to someone so some reading between the lines may be needed.

I calibrated them so that the bottom jacks of each section is centered on the screen. If you ever need to adjust them, they are super simple to set. When looking at the PCB, you will see two blue and white screwdriver trimmers. The one closest to the top controls the top section and the bottom is for the bottom section. Plug a patch cable into the bottom jack of the top section and the other end through your encoder and finally out to a monitor. Use a small phillips head screwdriver to slowly adjust the top trimmer so that center black part of the gradient is as close to the center of the screen as possible. Follow these same steps for the bottom jack of the bottom section and the bottom trimmer.

If you patch the ramp output into a Hard Key before the encoder, you can also use the Hard Key to remove the gradient effect and fine tune the black part of the gradient into a thin black line. Doing this makes it really easy to calibrate the ramps outputs.

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Thanks, i assumed this would be the way but the trim pots hit their end stop before I reach the centre.
It almost looks like the frequency is too low and the ramp is too stretched out rather than being offset.

I’ll get some photos tonight

Still having issues with this. The trim pots don’t seem to be enough to get them into the correct position.

Here’s a photo of the output. Patched the H \ / and V \ / outputs into a cadet fader to mix them, then into the key of a hard key generator.
This should give me a diamond in the centre of the screen right?

Using the trim pots turned all the way clockwise, i can get the attached image. I can’t move it any further left or up.

Has anyone got a decent image of a complete Cadet IV board i can compare to mine?


here is a picture of mine. the jacks are wired offboard.

Looks like possibly a wrong resistor value for the hramp portion. Try adjusting the resistor value that is in series with the trimmer to a lower value to increase the range. Also make sure you’ve used tight tolerance capacitors (use the exact partnumbers from the BOM or match to those parts’ specs.)

Thanks for your help guys, I ended up soldering another 499 resistor in parallel on the rear side (because lazy) and that got me in range to use the trims. Love this module! Now I can start testing a gamma shaper :wink:

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