I built the tonepad ross comp and I'm getting nothing at all.  I've tried using a multimeter to see where the signal stops but I'm evidently worse at that than actually building pedals  :? .  How do these things help in debugging exactly?  I set it to dcv and everything on the board is practically at 8.4v (the battery voltage).  What could I be doing wrong?

I had the same probl..a week ago w it..I said to hell with it then and changed some components and made the dyna comp!

good luck

Three VERY common sources of problem for first time builders are:

a) Component misorientation.  The variety of possible transistor pinouts out there is large, and the installation of the wrong pins in the wrong places inevitable.  Cap and diode misorientation also occurs.

b) Tha variety of stereo phone jack lug arrangements out there.  Even after about 28 years of doing this I still end up mistaking the lug arrangement of jack from manufacturer A with manufacturer B, the end result being no signal and a dead battery in the morning.

c) Solder shorts.  Good soldering technique is not only pretty, it also results in fewer solder shorts between traces on a board or between lugs on a switch.  In recent years, especially as I try to stuff more and more into the same small boxes, I've also taken to using heat shrink on my pot, jack, and switch lugs, just to be sure there are no accidental shorts.

These aren't necessarily the source of *your* particular difficulties, but they occur so frequently that it is always worth one's effort to check them out whenever a pedal does not fire up working the first time.

Greg, this is by no means meant to insult you but I have had this happen to me on about 4 pedal builds only to find out I didn't have a battery attached. Doh! (and the fact that you can't use the multimeter either may mean that in fact, you never hooked you battery back up).

Seriously, I have used the tonepad layout, it works. You need to double check everything, every wire, every orientation like Mark suggests. Then post the voltages at the opamp pins as well as the transistor legs. You CAN get it to work but as R.G. says "if you don't follow mother nature's rules, she can't help you"

Don't give up. I do have to say that that circuit is a tough one to do as your first effect.

Jay Doyle

This is my third build (TS-808 and Orange Squeezer) but I think I got a bit lucky on the first two.  

I'm using exactly the same transistors as tonepad lists and I've oriented them all as the diagram indicates, so maybe that is ruled out.  I also checked orientation of elec caps and they're ok.

There is a battery hooked up but I can see where that could happen.

I've double checked the phone jacks and that looks right too.

I studied the solder points and the circuit traces by eye and they LOOK ok, but since just looking probably isn't accurate enough, that's why I wanted to use the voltmeter to try and trace it down.  I'm also going to try the audio probe technique.  How does one actually use one of these anyway?

Thanks for the responses guys.

Hi Greg I had/have a similar problem with no signal so I went over every solder joint agin with the soldering iron so that I did not have a dry joint anywhere. This solved my problem to a point, I get a signal but my sustain only works for 2/3 of the range for some reason. Id give this a try.

Cheers

HL

Greg,

I highly recommed the audio probe.  It will take you 10 minutes to build it and save you hours of troubleshooting headaches.

Plug your guitar into the effect. Plug your other cable into the audio probe and the other end to your amp - this will be your output signal.  Clip the ground lead onto something and start probing around your circuit with the other lead.  The signal will come through your amp - when you don't here a signal that's most likely where the problem is. Great little invention.  I don't know how I got along without it.

AL

The audio probe is a good idea, and I should build myself one of those one of these days.  Until then, what you CAN do with your meter is to set it to the lowest or second lowest AC voltage range to measure audio signals.  Chances are nothing will be greater than a couple of volts, so if you have a 2VAC range that will be about right, 200mvAC in some cases.  You can use this to evaluate whether signal is getting through and whether it is being boosted by the amount you expect.

Plug your guitar into the pedal, attach your ground lead from the meter to ground.  If you use a Hammond-type box I find that simply sticking the end of the meter lead into the screw hole is fine.  If the circuit is out of a box you may want to use an alligator-clip lead of some kind.

The first place to check is where the signal hits the circuit, just to be sure there is nothing amiss with the footswitch or the lead going from the switch to the board.

If you see signal there in response to strumming, the next place to check is the output of Q1 on its emitter.  Strum all the open strings, and I would surprised if you measured something less than 30-40mv at that point.

The next place to measure is pin 6 of the 3080 (output), and if you get something there, then check the output of the transistor after it by sticking the probe at the emitter of that transistor.

Is the envelope-follower circuit behaving properly?  Measure the envelope signal at the base of each of the two transistors involved (or at least what you THINK is the base, where the cap, resistor and diode meet).  There should be something there that responds to strumming.

That's a start.

How do you have your 2K trimpot set? It should be right in the middle then slightly tweaked from that point.  Having it all the way up or down could also leave you with no signal.

Thanks for all the helpful suggestions.  I'll try the audio probe as soon as I can get to Radio Shack for some parts.  I'll get this comp working if it's the last thing.....(body thuds onto desktop) :wink:

Okeedoke.  I tested the pinouts and here's what I get (battery=8.38v):

Q1 7.13--1.76--1.24
Q2 6.65--2.33--1.73
Q3 8.16--0--0
Q4 8.16--0--0
Q5 8.34--8.16--7.65
this is looking down on the top of the transistor with flat part facing up.  I know that sounds like I don't know which is E, B, or C.  That's because I don't :oops:

now for the IC:
This is looking down on the top of the IC with dot in upper left corner (this is how the site from the FAQ has them pictured so I guess it's a standard).
1(dot) 0
2=4.2
3=4.2
4=0
5=0.67
6=2.3
7=8.3
8=0

A couple more questions if I might push my luck a bit more:
1.  On the site I mentioned from the FAQ (that lets you cross-reference trans., etc.  and shows the diagrams of each) and in the Mouser catalog, the picture of the transistor with the EBC below the pins--is this with the transistor flat side or domed side facing up?  I know that's a dimb question, but I wonder.

2.  The led on the comp pedal is EXTREMELY bright when the guitar volume is either all the way open or all the way closed.  This can't be normal.  It's blue and I used a 2.2k resistor if that helps.

Thanks in advance.

If you are using an LED as a status indicator, its brightness should be entirely unrelated to the guitar volume.  Something's not right there.

If you are using a 2N3904 or a 2N5088/89, the pins will be E-B-C, (left to right) looking at the flat side of the transistor with the pins pointing down.  If you are using a 2SC1815, those same pins will be E-C-B from left to right.  If you are using a BC546/7/8/9/550, those same pins will be C-B-E.

The voltages you provided.  Are those DC or AC?

Yeah, that LED thing is obviously wrong.  I've never even heard of that problem before.  I just don't know if it's related to the problem of no sound.

I have my meter set to 20 dcv. Are dc volts what a battery's power is measured in?  

They are definitely 2N3904.  I used everything exactly that Tonepad suggested.  So shouldn't the collector on Q3 and Q4 be getting something or is that an assumption I shouldn't make?