Troubleshooting my first test rig- (now fixed and boxed!!)

[Om_Audio]

Hi- meet my new Frankenstein test rig!

Hoping someone can suggest an error. I went for a more complex test rig than the basic one. I am 99% sure I do not have any solder bridges or bad joints. I am suspecting the pot wiring but not sure.

PROBLEM:
Not getting V through the black/red test leads (w alligator clips) while on DC jack but works (including sag which is an Alpha 1K pot) on battery (tested w DMM).
/PROBLEM

LED works on batt w 1/4" in input. LED works on DC jack power with or without 1/4" input. 2nd DC jack not wired but eventually I want it to be on sag like clips. Also I do not currently have a circuit to use the test rig on- what I did was used a spare battery clip to try and power a pedal with and to test the sag function.

I went off various info- Beavis, main test rig thread here, and this build thread by Josh (gtr2) w sag- http://www.madbeanpedals.com/forum/index.php?topic=784.0
But mainly I used the MB standard wiring diagram for main reference.

Connections as currently wired:
+9V on jack--> LED/resistors, +battery clip lead,  far left lug of pot (referenced pic in Josh's thread)
-9V on jack--> sleeve of input 1/4" jack (verified grounding through chassis for all ground points and with 3PDT switch in both positions)
Test leads:
input (green)--> center lug on 3PDT
output (yellow)--> upper right lug on 3PDT
+V (red)--> middle lug on pot
-V (black)--> middle row far left lug on 3PDT

Far right lug on pot--> resistor to ground (3 resistors equaling 2.2K)

On slim chance a photo might be of use in diagnosing...

[electricstorm]

The single red wire from the DC jack going to the three resistors on the left side, where do these go(what does the three resistors attach too)?

[Om_Audio]

The LED. I had to use 3 resistors as I didn't have correct value on hand. Thx,
C

[nzCdog]

Sorry man, I'm finding your explanation a little difficult to understand...
What are you tryin to do?
Whats not working?
Are you running the LED/resistors in series with the Sag pot?
Have you wired up the pot Lug 1 = VDC in, Lug 2 = V-Sag Out and Pin 3 = Ground?

[Om_Audio]

1- What are you tryin to do?
2- Whats not working?
3- Are you running the LED/resistors in series with the Sag pot?
4- Have you wired up the pot Lug 1 = VDC in, Lug 2 = V-Sag Out and Pin 3 = Ground?

I tried to make orig post clearer, sorry bout that.

1- determine why I am not getting voltage from black and red voltage test leads while using the DC jack with a wall wart.
2- as above
3- no (LED is: + to resistors then to + on DC jack, the - goes to top upper left lug on 3PDT switch)
4- yes I think so- I did it same way as Josh (gtr2) did- but I am not clear on pot lug numbers. If you look at the photo the lugs from left to right are as you describe. (lug 2 goes to the red test lead for +DC V)

I have found differing pictures and descriptions as to pot lug numbering. I just made sure I mirrored Josh's picture. Is it correct to assume that looking at the back of the pot with lugs at top that numbering would be 1-2-3?

Thanks a lot for the help,
C

[nzCdog]

In terms of pedal wiring...

Those DC jacks are switched and normally have 2 solder tags to the +VDC
When no DC plug is in the socket, both +tags are 'on'
When you put a DC plug in the socket, one of the +tags turns 'off'
This is to disconnect the positive battery connection when a DC supply is plugged in... the 'Off' + Tag goes to your battery, the 'On' + Tag goes to your circuit.

See the Madbean wiring diagram or use your multimeter to check which is which, it sounds like you have them mixed up.


Pot legs/pins are numbered from left to right, 1,2,3 when the shaft is pointing up ↑
You are creating a 'Voltage Divider' to control the voltage with that pot
I would wire it like this:

Pin 3 > +9VDC
Pin 2 > +V Sag Output
Pin 1 > Resistor (1KΩ) > Ground

That would allow you to adjust the volts from 9VDC to 4.5VDC woth a 1K Pot.  You could try a lower value resistor in there, say 470Ω if you wanted to get lower Output Volts, but if use a much lower value and it will start to get hot.

[Om_Audio]

Oh man, this is great, thank you! It works!

I had no idea those DC jacks worked like that. They are the jacks from the Boss TU-2 I am using for the build- I thought it just had 2 tabs for +V for convenience. I just tested it and indeed, the outer tab shuts off when adapter is plugged in and that is where I currently have pot lug #2 wired too. I just tested a new uninstalled jack for a project and same result- I learned something new and VERY useful about DC power jacks for pedals!

It works great now, sag is VERY fun to experiment with on pedals! Tried it on 2 old Arion boxes I didn't care if I damaged in case I still had something wrong with the test rig (a distortion and a delay). The distortion pedal does some cool pulsing and response to guitar attack and the delay repeats begin to break up a bit and get cloudier. i could actually see a sag knob being good for certain pedal circuits as the results are interesting! The current resistor value I have of 2.2K seems ok actually- both pedals I tried it on stopped working entirely before the pot reached the end of it's travel- had a bit more travel after. I think I will take your advice and try 1K though. (I did switch to 1k works good)

I reversed the wiring on lugs 1 and 3 of the pot is so as you rotate CCW the voltage sags rather than the reverse which is how it was before, thanks. That is why you suggested that, correct?

Would it hurt to have 3 wires off lug 2 so I could run the LED from there as well? Would be cool to have the test rig LED reflect the sag knob position.

Also, there is DCV on the test leads regardless of the 3PDT switch and I assume this is how it is meant to operate?

I am SO EXCITED.

THANKS AGAIN!

C

PS- PS- I got the 2nd DC jack working but was never able to get it to sag below 9V so I unhooked it to be safe. I tried it off lug 2 of the pot. Will try to sort out the 2nd DC jack at another time.

Saaaaaag......  

[nzCdog]

Woo!  Great Job Clifford, let the Sag begin!   
Yes you could run your LED from pin2 of the Pot as well... try connecting it Pin2 > Resistor > LED  > Switch... If it doesn't seem to grow dim enough with 'Sag' you could try a larger value of  Resistor for the LED, say double it and see how you go... 

[Om_Audio]

Thanks man, I had excellent assistance! I just got "a few" boards in the mail today (see below).  

I will be putting this tester through its paces for sure!


When you describe LED hookup you mean LED positive to resistors to lug 2 and LED negative to switch, right? I try to describe connections wire by wire, not sure if you are doing same or describing both + and - LED connections, thanks.

Also, I have yet to put an audio probe in so that will be next thing I add maybe later today.

C

just a few...

[Om_Audio]

I added a probe- made it out of solid core wire, toothpicks and shrink tube- about as DIY as it gets. Not sure if I like the solid core. I also put the probe on a switch but it is not needed, I thought it might reduce noise.
I am finding the probe VERY interesting to use. Pictured is a Rocktek delay which I unboxed and soldered some resistor leads to the i/o tips on the back. I am using an old iPhone for audio (John Coltrane's "Ole' album and soundtrack to Paris, Texas- )

At different points I discover places where there is ring modulation as you twist the knobs, overly filterd spots, super high top end spots, places w clean audio, places w no audio, noticing certain pots dont have the effected signal making it clearer that they are simply controlling a part of the circuit etc. It turns gears in my head thinking of how certain things are dealing directly with the audio signal and other things are not and so forth. All of the sudden basic circuit bending seems so simple and possibilities vast after finding these results! Fun!

Question: Why do some folks put a phase switch on their test rig? Also, is there any need or benefit to having a switch to switch =between= probe and alligator clip lead rather than just switching the probe in and out? Is there any reason for not having both probe and output lead active at the same time and switching them instead?

C