Help with Slope Detector

abelovesfun · Joined: Dec 17, 2012 Posts: 40 Location: Portland, OR

Hello,

I've built many Ken Stone designs and love them. I've even had good luck with some "difficult" builds like the VCS. For some reason I'm having an issue with the Slope Detector (version 1.2).

I completed an exhaustive point to point audit of the components, and have confirmed that everything is wired up correctly, but my LED's just won't light up... unless... for some reason if I flick the plastic proto panel (I usually build into a plastic panel before I buy a bridechamber) the led will light up.

The trigger out works, and for some reason the Rise out sends a constant gate signal.

Any clues? I've swapped out the TL072 to no avail.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

wackelpeter · Posted: Wed Jun 24, 2015 12:27 pm Post subject:

Sure it's the Trigger out of the rising period that sends out a steady Signal?

i've built it on stripboard and i can tell that when nothing is connected to its Input then the steady Output is always on or activated...

are there Trigger out's on each of the 3 Outputs? does the sensitivity pot respond?

do you have a scope to do some test's?

do you have measured the outputs of the comparator op-amp with an slow triangle lfo?

anyway if it's just one of the led's didn't lighting up and the rest work and the led do light when you tip the board than it should be a bad Connection only... if the Output corresponding to that LED does work...

abelovesfun · Joined: Dec 17, 2012 Posts: 40 Location: Portland, OR

Thank you @wackelpeter!

Sure it's the Trigger out of the rising period that sends out a steady Signal?

I am certain.

are there Trigger out's on each of the 3 Outputs? does the sensitivity pot respond?

I am not seeing triggers being sent from any of the outputs, regardless of the sensitivity pot or switch setting - with the exception of the Rise, which is always on.

do you have a scope to do some test's?

Not yet, but I bought one two days ago and it should arrive between tomorrow and next Tuesday. Until then it's just my DMM and my modular for testing.

do you have measured the outputs of the comparator op-amp with an slow triangle lfo?

Not yet - what pinout # would that be?

anyway if it's just one of the led's didn't lighting up and the rest work and the led do light when you tip the board than it should be a bad Connection only... if the Output corresponding to that LED does work...

As of now, none of the LEDs work unless I flick the panel really hard. I have to flick the part of the panel near the led/jack for the led to light. I have tested for continuity and I have it.

wackelpeter · Posted: Wed Jun 24, 2015 12:54 pm Post subject:

the Outputs of the comparator are 1&7 of the tl072...

i just remember that i had some similar behaviour when no slope was connected to my slope Generator... when i pushed my synth-box a more whilst unplugging cables or by accident the LED briefly light up... but that was just a bad Connection of either the positive or negative power rail in my Distribution board...

the Outputs on pin 1 and 7 should be the opposite of each other... means if 1 is high then 7 should be low and vice versa...

but if you have an scope then things would be much easier to detect...

maybe you can meanwhile post some better pics of your board component side and layout/traces side... maybe there is something you haven't spotted yet...

abelovesfun · Joined: Dec 17, 2012 Posts: 40 Location: Portland, OR

Scope doesn't arrive until Tuesday Sad

Until then here are close ups of the top and bottom. Pay no attention to my OCD continuous ground wiring! Unless that could somehow be an issue?

Posted Image, might have been reduced in size. Click Image to view fullscreen.

wackelpeter · Posted: Wed Jul 08, 2015 6:29 am Post subject:

so any progress until now? did the scope arrive?

Mine died last week... Sad

a lot of smoke was coming out of it... after replacing fuses with some smaller ones as the original are, i did a restart then and it works to some extend but i couldn't get it focussed anymore... looking at the graphs i can now roughly speculate what it Shows me...

abelovesfun · Joined: Dec 17, 2012 Posts: 40 Location: Portland, OR

Scope arrived. Still learning how to use it, but I've tested waveforms and envelopes. I'll be testing the slope detector tonight - thanks for checking in!

abelovesfun · Joined: Dec 17, 2012 Posts: 40 Location: Portland, OR

Ok, plugged it in. I think my scope is a dual channel, but only one seems to work. Here is a video showing nothing probed, then pin 1, and then pin 7.
https://www.youtube.com/watch?v=XHFrdzg6Pi4
Any clues?

abelovesfun · Joined: Dec 17, 2012 Posts: 40 Location: Portland, OR

Turns out it was a cold solder joint. Fixed!!!