New testing rig

[jkokura]

Hey everyone.

So in my new digs, I'm a little limited - ok, a lot limited - on space. I now build in a closet. My bedroom closet to be precise, which also still functions as a closet along with being my building space. Not only that, but because we're in an apartment and my newborn son sometimes sleeps less than 10 feet from where I build. I keep most of my guitar gear in my office at work now, including most of my guitars and my 'gigging' pedal boards and such.

So, I had to come up with an efficient testing setup. What I was doing was taking my finished and wired boards with me to work, finding a moment to test them out with my guitar using my previous testing rig, and then if it worked great! But if not, I was really limited on figuring out what the problem was. I decided to build a system that would work almost silently using the headphone amp project I have developed. I also wanted to not have to use a guitar - I'm sure you guys have figured out how hard it is to test a circuit out while simultaneously playing guitar. So I decided to include the tiny oscillator project I developed as well. Lastly, I wanted to be able to bypass the circuit being tested, which my old test rig doesn't do and I wish it did. Here's what I came up with:



And the Guts.



If you look carefully, you'll see that the left jack is the output, and it's a stereo output directly connected to the headphone amp. The headphone amp is connected directly to the bypass switch, one half of which is connected to the input and output alligator clips for the testing setup. Into the bypass switch is a toggle bypass switch setup to bypass the oscillator. This enables me to turn the oscillator on an off, also allowing me to include an actual input for a guitar input. This is also handy for testing things like delays, which don't really work with a single sustained tone. I can turn the oscillator on and off quickly, allowing the signal to repeat.

The only additions that could be/will be made would be a probe. I will likely install either a SPDT or DPDT toggle underneath the toggle there already to be able to switch to the 'alligator probe' or the 'audio probe' for testing. This is handy because sometimes it's better to be able to use an audio probe in this stage of testing. Plus, using the oscillator allows me to use both hands to probe and make notes on my build docs as well. Oh, and I put knobs on it already as well.

Hope you've enjoyed,

Jacob

[cab_eleven]

That is awesome.

[sgmezei]

This is slick Jacob. I still use mine that I built from your other thread all the time. I want to put an oscillator and headphone amp into it as well, but haven't hunkered down to do it yet. The oscillator would be a huge plus so I don't have a guitar in my lap getting banged into the desk trying to debug.

Handy!

[jkokura]

Yeah, the big thing for me was the silent testing and the no guitar factor. Trust me, since I finished this last night I've debugged two builds and have almost found the problems on two more!

I used an already drilled blem enclosure for this one, so it made it easy to do. I can't imagine just buying an enclosure for a test rig. I had no purpose or use for this enclosure, so it made sense to do it.

Jacob

[Om_Audio]

Would you mind expounding a bit on how you use this testing rig? I'm new to pedal building but i do understand the concepts of audio/circuit testing but not really in practical terms. a little bit of insight into how you actually use this to test a build would be most appreciated!
Om

[saxoftenest]

Umm...  WANT.

I will be building this ASAP, it's f'ing brilliant.

[Jargo]

Yeah!!!   +1

[jkokura]

Would you mind expounding a bit on how you use this testing rig? I'm new to pedal building but i do understand the concepts of audio/circuit testing but not really in practical terms. a little bit of insight into how you actually use this to test a build would be most appreciated!
Om

No Problem! If this isn't clear, let me know and I'll make a video.

1. I populate a pedal circuit board using my usual process of selecting parts, making sure they are correct, installing them neatly and carefully soldering them in place. Once all that's done, I add the potentiometers, usually using left over cap and diode leads to create my own pcb mount pots using the usual solder lug kind. Once that's done, I add in the four major wires needed: In, out, ground, and +9V.

2. Once the circuit is fully populated and wired up, I take out my testing rig, headphones and 9V DC supply. I plug my headphones in, plug the DC in, and then check to see that my oscillator is running and my headphones are working. If I didn't have the oscillator or heaphone amp installed, I'd have to plug my guitar and amp in, and I would check to make sure that the guitar and amp working right.

3. I then use the alligator clip wires coming out of the test rig to hook up my recently finish board. I usually hook up the ground wire first (green clip above). Then I will hook up my input (yellow) and output (black). Last I'll hook my power (red). I'll wait a second or two, feeling the IC's and transistors, and watching for any issues to pop up on the PCB - sometimes you'll find out you've put a part in backwards or incorrectly right now, because things will start to heat up. It could be a good idea to wear safety glasses if you're worried about a part blowing.

4. I turn all the knobs on the effect fully CCW (or off). Once that's good to go, leaving the oscillator off, I hit the bypass switch and turn the effect 'on'. I then turn the oscillator on, and slowly begin to bring up the various knobs on the effect. Most of the time I get the expected response from each one, and in that case I know my circuit works and I then can box it up!. Sometimes though, nothing happens. If nothing happens then I start my debugging process.

Jacob

[Om_Audio]

Thanks very much. I was making more out of it than it was. I have heard of probes and testing parts after installation etc. Your setup is much more straight forward. Thanks for the insight!
Clifford

[Ettore_M]

I was looking for  a testing rig like this. It's simple and straightforward, and it has everything you'll ever need! That's awesome!
Thanks, Jacob!

[bigmufffuzzwizz]

Great idea installing the test oscillator right into the box. Now doesn't using alligator clips make it super simple to test? And you can use them to probe through circuits...Sometimes i use them to apply power directly and find out the DC jack doesn't work or it's wired incorrectly..endless possibilities!

[nzCdog]

Thats very cool Jacob... very

[Jabulani Jonny]

I hate to revive an old topic, but I'm getting ready to build a testing rig and I'd like to implement the tone generator referenced here.  I know that Jacob has them available on his site and I'll probably just spring for the PCB. 

However, I'd love to get some input on the connections for the DPDT switch to implement that tone generator and an audio probe.  I already have an audio probe that I was going to add to the testing rig, but it would be awesome to implement both. 

For my last build I plugged my iPhone into the pedal's input with a 1/4" to 1/8" adapter to debug.  I have no doubt that I'm playing with fire doing that, but not really sure what kind of fire.   

So any help on wiring in the DPDT to implement the tone generator and audio probe would be much appreciated.  thx. 

[jkokura]

Sure.

I'm working on a new version complete with build docs for a kit that's going to be release from Mammoth. If you give me some time you'll get the full skinny from there.

But really, both the probe and oscillator just need bypass switches. It's not too complicated. If you need a step by step, here's what I would do.

For the tone generator, I would have the generator attached to lug one of a SPDT switch, and the 1/4" jack attached to lug 3 of the SPDT switch. The common, lug 2 of the switch is your output. It may be need to use a DPDT switch that will allow you to ground the oscillator so you don't get bleed through tone, I'll be working this out in my upcoming reworked version.

For the probe, it's really simple. a SPDT switch will switch between your ouptut alligator clip and the probe with a 100nF cap in series. Lug 1 is the probe, lug 3 is the alligator clip, and the common is your return of your bypass switch.

Jacob

[Jabulani Jonny]

That makes sense.  I was just trying to think through if I could put the oscillator and the audio probe on the same bypass switch to simplify a bit, but I don't think it'll work like I was thinking.  So on your rig in the pics above, the oscillator board has a ground, but you're not grounding oscillator output of lug 1 on the DPDT, right? 

So basically one DPDT to switch between 1/4 input and oscillator as you have up top and an SPDT to switch between audio probe and alligator clip of the circuit output.  Seems straightforward enough. 

I'm actually not using the alligator clips, opting to go with terminal strips instead, like on the Beavis Board.  So I'm basically modding the Beavis Board test rig with your oscillator (ordered today BTW) and an audio probe.  This should really aid my troubleshooting, but also allow for a fairly simple bread board set up as well. 

Many thanks!