Finishing up my first stompbox today...

[weston5952]

But I have a few questions first. I am making the rodent

http://www.generalguitargadgets.com/diagrams/rodentpl.gif

but I am using two mono jacks instead of one mono and stereo. Since I will be insterting a mono cable the ring and sleeve are the same thing right?  So I can solder what would go to the ring on a stereo jack to the sleeve along with that ever is supposed to go to the sleeve accordeing to the diagram above.

Also, even though my jacks are mono they have three terminals and it looks like two of them go to the tip. Why is this?

And finally I am a bit confused to what I need to 'isolate" I know i need to isolate my jacks and power jack but what about the switch? Thanks so much for your help.

[Samuel]

the only one that really needs isolation is the power jack - I personally use plastic body power jacks for this reason. The switch is self-isolating (no contacts are electrically connected to the switch body) and it's perfectly fine (and desirable!) to have the sleeve connectors of the in/out jacks ground to the case.

The problem you will run into by using a mono jack instead of stereo is that there will be no way to turn the battery off without unplugging it, it will drain constantly. You would either need to unplug the battery everytime you are finished using the pedal (bummer), or install a power switch. Or, as option three, not include a battery option at all

Your jacks have three connectors because they are "switching" jacks. You will notice that one of them connects to a tab of metal that rests against the tip connector. When a plug is inserted, it pushes the tip connector away from this tab, breaking the connection. This is used to allow *something else* to connect to whatever the tip of the jack connects to when there is no plug inserted (think about optional expression pedal jack, or fx-loop jack behavior...)

[mindwave_21]

Samuel is right.  You need a stereo jack for input, but you can use a mono for output.

[weston5952]

Thanks a lot Samuel! I wasn't planning on using a battery anyway so that will work out fine. And it will be much easier to isolate just the power jack. I will get to work right away. Thanks again for your help.

[weston5952]

Oops. Just rememberd one more thing. My power jack has three terminals. I can tell that one goes to the sleeve and I assume that the other two both go to the pin... is this correct? If so I can wire the ground wire to either of the pin terminals?

[NaBo]

yeah, the reason people use a stereo jack (usually for input) is for switching the battery on/off.  just for a bit of clarification on how that works (cuz i know learning that much helped me figure out the ins and outs of wiring these things):

see, you have all your grounds connecting to the sleeve lug, and the battery/dc neg. lead attached to the ring lug...  thus, when you plug in a mono jack, the ground connection gets completed by the sleeve, and the juice can flow!  taking the jack out when you're done breaks the connection, so your battery doesn't drain.  you dont NEED to include this feature, but its easier to disconnect your cord than it is to disconnect the battery (unless you use an on-off switch, which is a waste of space and kinda strange).  of course, as Samuel said, if you're using dc power without a battery, you dont have to worry about any of that, and you can save a few pennies just getting mono plugs  

i bought a bunch of those switching jacks on the first parts run that i made, too... i just snapped off the extra lugs on those.  generally, dont buy those, you dont need them for most things, and they're more expensive.  save even more pennies!

and, as Sam said, you can just use plastic-bodied DC jacks to keep them isolated.  the only thing about using those is that you have to screw them in from the OUTSIDE, so you can't solder them before putting your circuit in a box.  depending on the type of enclosure you're using, that could be a HUGE pain.  the non-isolated metal type, i THINK you can install from the inside like all your other jacks and the switch, but you'll have to use a rubber gromet to isolate it from the enclosure.

hope i haven't just restated stuff thats already been said   ... say, out of curiosity, where did you get your LM308, and how much did it cost you?

[H.Manback]

About the three terminals, I'm guessing you have the lower right one of these jacks:


If so 2 terminals aer tip and sleeve, and the third is a switch connected to the tip. As you can see it is normally closed, and when you insert a jack it's open. Good practice is to connect that to the ground (it is on amps anyway), so that when nothing is connected, no signal is applied.

[NaBo]

Oops. Just rememberd one more thing. My power jack has three terminals. I can tell that one goes to the sleeve and I assume that the other two both go to the pin... is this correct? If so I can wire the ground wire to either of the pin terminals?

i see where you're getting confused... the wiring diagram for the rodent is a little less clear than JD's others (with the cool little pics of the jack ).

the middle lug on a DC jack is used for battery switching.  you connect the positive lead of the battery to that one (the rodent layout just makes this connection through a small pad on the board for some reason).  its so your battery turns off when a dc jack is plugged in.  look inside the barrel of the jack... see that little piece of metal thats hanging down?  thats connecting the middle lug to the top one, which goes to the 9V+ of the board.  the positive end of the battery is connected to the board THROUGH the dc jack.  and, when a jack is inserted, that connection is broken and the electricity stops flowing from the battery.

i suggest you take a look at the "switching and wiring" section of the tech pages at GGG, all this is explained better and with diagrams

[Samuel]

NaBo is correct - although I think most people wire their DC jacks in the opposite manner he suggests - with the pin of the DC plug being negative, and the sleeve being positive.  (It is the sleeve connection that gets switched in and out on these jacks)

As he said, the principle of the switching terminals is precisely the same as the switching 1/4" jack - for most people this means they can allow the pedal to operate on battery power "automatically" when there is no DC plug inserted, by routing the (+) end of the battery through the DC jack, so that when a DC plug is inserted the battery's (+) connection is cut off from the circuit.

[NaBo]

NaBo is correct - although I think most people wire their DC jacks in the opposite manner he suggests - with the pin of the DC plug being negative, and the sleeve being positive.

ahh, nonono, sorry about that, i should have been clearer... i didnt mean the middle lug as in the one that goes to the pin, i meant the lug in between the pin lug and the sleeve lug... ehhh... maybe i should've just linked to a diagram, like so: http://www.generalguitargadgets.com/diagrams/switch_lo_dcjack.gif

there, he's bound to get it now ... though he probably already has the thing fired up and we won't hear from him for a few days :wink:

[weston5952]

Thanks for the info on the jacks, it helped me understand a lot. I just finished  wiring everything in place and plugged her in to test her out. She did not work. I have no idea why, but maybe you guys know. This is what happened when I tested it. The peal works fine when in bypass mode (though there is a bit of noise). When I hit the switch to change turn the effect on the LED comes on but no sound at all comes out. I messed with all of the pots but still nothing. One other weird thing is that when the pedal is in bypass mode the volume pot turns the LED on and off? I checked over my wiring but maybe I missed something. I will post a pic to let you guys take a quick look. You will notice that I left out the battery and that the DC jack is not installed in the enclosure yet. THanks so much for you guys help!

[Paul Marossy]

Are you sure that the all the foil leads on the PCB have continuity? From the picture, it looks like some of them might have not etched well. The other usual things to look for - wrong component(s) used, forgotten ground, something miswired, bad part, etc.

This sounds like a job for the audio probe! http://www.diyguitarist.com/PDF_Files/DIY-AudioTester.pdf

The other thing to check for is if your power supply is being shorted. If you use a metal center negative power jack with your enclosure, you will short out your power supply. I did this on my first build...  :oops:

[weston5952]

The foil leads on the PCB look solid throughout but they aren't too shiny. A few of them were real skinny too so I just made a little solder bridge when I was soldering the components to the board. I went through and rechecked my wiring and the parts and everything looks good. Would it be benificial to go through the circuit with a multimeter and check for volatge or current? If so, how do I set the meter and what should I look for. Again, thanks so much for your help.

Oh yeah, my power supply is not being shorted because I get power to the led and it's not even mounted in the enclosure yet.

[NaBo]

instead of the audio probe, you might want to use the audible continuity test on your multimeter, if you have it.  it's on my 18$ one .  it definitely sounds like it could be a broken connection in the signal path when the effect is engaged, and some of the traces do look a little suspect, in that picture anyway.  i usually go over all my traces with a thin layer of solder (cuz i dont tin or lacquer or whatever else people do to their boards), just to make sure and to keep the copper from oxidizing. you can also use continuity testing to double check your wiring.

check your transistor pinouts and placements as well!  on one of my first builds, a green ringer, i had a 2n3904 and a 2n3906 switched, and i had the same problem - no sound when engaged.  it drove me crazy until i realized "... oh, Q2 and Q3 are reversed.   :oops:" ... so it could be that.  i think if you just had reversed the pinout on one of them, you would know, and it would make a deafening whine when you plugged it in, and possibly cooked the transistor.  i done that before too...  :roll: ... CHECK THE IC TOO.  im sure you put it in the right way considering the price most places are selling LM308s for, but you never know.

it sucks when you get all excited cuz you THINK you're done and are gonna be playing through it within 5 minutes, but debugging is a part of the build process too.  everybody's human, and everybody makes mistakes once in a while.  so roll up your sleeves, grab your meter/audio probe, and let's get this thing working!

[weston5952]

Thanks for the encouragement NaBo. My transistors are good as is the IC. I also checked all of the polaraized caps and diodes to make sure they are aligned correctly which they are. I guess I will go over all my traces with solder as you suggested just to make sure that none of them are broken. My multimeter does notends to see if they have one with that feature. I was messing around with my meter checking voltages (even though I have no idea what I am looking for) and found tha have and audible continuity test but I will check with some frit there was no voltage anywhere along the trace that I circled in red in the picture below. Don't you guys also find it weird that the volume pot controls the LED when in bypass mode? It seems like that could be a wiring error but I have double checked the wiring too. Debugging is very frustrating. :cry:

[RickL]

Is it possible that you have the switch rotated by 90 degrees? If the switch is wired correctly the LED should be completely disconnected when the switch is in the bypass position. This might also explain the noise you're getting in bypass.

Use your meter to confirm that the input jack is connected to the input of the circuit and the output jack is connected to the output of the circuit when the switch is in the 'effect' position. In the bypass position the input jack should be connected directly to the output jack and the input and the output of the circuit should be connected to nothing.

[weston5952]

RickL, it would be really difficult to rotate the switch without knowing. I am using a DPDT switch as shown in this layout:

http://www.generalguitargadgets.com/diagrams/rodentpl.gif

I see what you are talking about if I was using a 3PDT. I did begin to read some more info on switches and noticed that the wiring in the layout is different than most of the example wiring patterns od DPDT swiches such as the ones on this page:

http://www.generalguitargadgets.com/pdf/ggg_intro_switches.pdf

They all connect the two bottom or top terminals. I hope the layout isn't wrong which I doubt would be the case.

[weston5952]

okay, i just finished checking all the traces on my cb with my multimeter. They are all good and there are no solder bridges where there arent supposed to be. I still think that my wiring is bad but I keep checking it agaisnt the layout and cant find anything wrong. let me double check a few things with you guys. According to this layout:

http://www.generalguitargadgets.com/diagrams/rodentpl.gif

when wires run to the pots are they illustraed with the shaft pointing dow into the computer screen. Thats what seems logical and is how I wired them also. Is the switch correctly illustrated because I just wire to my switch relative to the pictured switch. I am getting really sad about this not working. :cry:  so thanks for all of you guys help and expertise

[RickL]

Oops!  :oops:  I looked at the picture before I posted and it looked like a 3pdt switch. Time for new contacts.

[Paul Marossy]

I was suggesting the use of an audio probe to see where the signal dies. If you haven't already done this, you need to measure the voltages at all of the transistors/opamps, etc. to see if they are getting the right voltages. Also, the volume control should not have anything to do with the brightness of the LED. It sounds like something is wired incorrectly to me...  

I would suggest putting it away for a couple of days and coming back to it. I usually find my stupid mistake when I come back to it a couple of days later.  :oops: