Need help with Engineer's Thumb compressor build

[LoonDawg]

Ok, so I just finished building an Engineer's Thumb compressor and it is not working. In the past (since I am still relatively new at pedal building) I would just get frustrated and put it down, never to pick it up again. I am not the best at debugging or getting to the root of problems, but I am hoping to get better and I am hoping that someone here can help me get this pedal up and running.

Here is the layout for veroboard. http://www.sabrotone.com/wp-content/uploads/2012/05/EngineersThumb.gif

Here is the bottom of the veroboard with cuts and some of the jumpers

http://imageshack.us/photo/my-images/801/stf3.jpg/

Here is the top of the veroboard with all the components and the rest of the jumpers

http://imageshack.us/photo/my-images/14/ppr2.jpg/

Here is the inside of the box (it is a tight squeeze so you may not be able to see everything, but I believe everything is correct though I am probably wrong which is why I'm here :-)

http://imageshack.us/photo/my-images/36/wz5i.jpg/



The sound passes through when the pedal is switched off but there is no signal when it is switched on. Also the LED doesn't light up which is a red flag, but I have a 1k resistor on the LED and it should be wired correctly. I checked to make sure I put the resistor on the correct side (not the cathode)

I think I used all of the correct parts, the only question might be the capacitors (C5 and C6 were 1uF Tantalum Capacitors from RadioShack) and the others I had to order online and I got the correct ones (I believe)

I can't see any shorts on the VB and I went back through with a knife to make sure that there wasn't any accidental points touching.

I will keep looking but I am hoping someone can see something obvious or help walk me through tracing back the signal path. I do have a multimeter thing but I don't really know how to use it (I only use it on the setting that makes noise when there is a connection)

Thanks




I also just found this http://www.madbeanpedals.com/forum/index.php?topic=6206.0 and am going to read through since it looks like someone was doing the same build and ran into an issue. Perhaps it was the same thing.

[GibsonGM]

1) don't give up, or get frustrated...talk a walk, come back to it...

2) read this:  http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Do you have an actual SCHEMATIC for the thing you can post? You can't tell squat about a circuit by Vero, man!  At least, not without really going into it.  Fast with schem.


The problem is usually (99% of the time) something that is, well...how to say this....DUMB.   I've done it, you're doing it, everyone else has done it.   Something you shorted, bad soldering, a broken jack, dead battery....now you get to start learning debugging skills, which you can take to ALL kinds of other problems, electronic or not!

So - get reading, post voltages etc. as described in the debugging thread, and let's see if we can get you running!!    Glad you're trying to fix it rather than walking away 

[LoonDawg]

Thanks, how do I go about getting voltages? I have a multimeter but don't really know how to use it very well.

Also, I have a schematic that was cut off during printing but since I can't read them very well, I don't use them often (bad excuse but it's true). I just tried to find it again to no avail. I will finish reading the debugging article and see what I can narrow down tomorrow.

Thanks, and any more help would be greatly appreciated.

[LoonDawg]

Found it

http://dl.dropboxusercontent.com/u/57831278/EngineersThumb5Knob.jpg

This should be the right one, or at least close. It is the 5 knob version that I am building

[GibsonGM]

To read voltages, set your meter to "DC" volts...some say "DCV", or just have a dashed straight line.
Connect the black probe to the "-" of your battery.    Use the red probe to read voltages on component pins.  Do NOT touch more than one spot at once or you may short the transistor, chip etc you are probing!!!!   It takes a steady hand )   Definitely a MUST HAVE skill. 
Work at it, and it will become second-nature...so will reading schematics!

OK - the "Thumb" seems to be a pretty advanced build for someone...kind of new....but if you can get some voltages posted, we might be able to at least point you in SOME reasonable direction to start!   I mean, right now we don't know if your battery is dead, or wired backwards....y'know. 

Try to fill out the 'debugging' info as best you can.  Battery, opamp voltages are crucial here.  If the 1N4001 is in backwards, the circuit won't work, BTW.   Be careful measuring the pins on the opamps!!!!  Go slow and steady.

[LoonDawg]

Thanks, I will get on that soon. I don't have a battery wired in, just a 9VDC jack wired in but I will do tests with a battery

[GibsonGM]

Thanks, I will get on that soon. I don't have a battery wired in, just a 9VDC jack wired in but I will do tests with a battery

Good idea, keep it simple!  You could VERY EASILY have the jack wired up wrong...I would remove it, and apply my power right to the board "+" wire.  Take it all out of the box for troubleshooting.  I don't pack anything until I KNOW it works!  Really, it could be as simple as a solder bridge between 2 things that shouldn't be connected.  The trick is to go back over every connection, over and over.  PITA, but necessary... 

[LoonDawg]

I checked the voltages (using the 20 setting, assumed 20V and I didn't want to overdo it) of the board and have uploaded an image of the results which I hope is readable.

http://img59.imageshack.us/img59/8748/jfpf.jpg

I have not done the pots yet (should I do that?) and I also think I didn't wire up my DC jack and switch properly so I am going to bypass that and battery power to continue to test.

Does anything stand out as being wrong? I'm also not sure what kind of variance is ok in the voltages but there were a couple places that seemed odd to me (but I am new to this). IC3 point 8 measured .30 and also the resistors R2 and R8 all measured 0 on both points, is that just a ground? Why put resistors on the ground?

Thanks

[LoonDawg]

It looks like it may have just been a power/switch issue. I wired it directly to inputs/outputs and the battery and it worked, although there was a buzz. Now I am wiring it up in the case now and will suss out the correct way to wire up the DC jack, led and switch.

I hope the buzz will sort itself out but any ideas on how to reduce it? Should I wire the ground to the pedal itself or will the ground happen when it is plugged into the amp?

[MrStab]

hi Loon, welcome to the forum! the Engineer's Thumb is a favourite of mine, and i've built two from the same layout as you.

I have not done the pots yet (should I do that?)

you mean you haven't tested the voltages of the pots, or you haven't hooked them up? cos you'll need to hook them up for the circuit to work properly. just checking.

are you using the 5 knob version? if so, it's worth noting that there are some "broken" settings which'll be noisy and unusable unless you do some tweaks. just set everything to the middle (except maybe Attack, keep that fully anti-clockwise) for now. also, when the settings do work, with Ratio and Threshold on full it'll amplify the hell out of any pre-existing buzz. it's even noiser with no guitar connected.

this is an over-simplifcation, but just make sure all grounds are connected to each other - preferably not more than once - and are connected to the battery or DC jack negative tip. don't worry too much about grounding to the enclosure just yet, but you will need to eventually (usually this is done by just bolting the input or output jack against the metal).

sorry if i've misread something. hope this helps!

[LoonDawg]

The pots are wired in but I took everything out of the box to check voltages and connections. Now I am having trouble again though. The switch seems to be working but I am testing connections with some alligator clips and when the switch is on, something is not getting through. So it is close but still not all the way there yet.

It is the 5 switch version. Since you have some experience with this one MrStab, what are the "broken settings" and what tweaks can be done? Is it on the circuit side or is it more of a settings of the pedal thing?

Thanks for the help

[MrStab]

iirc, the worst offender was the Release pot. when Release is turned to 0 and Ratio/Threshold are quite high, there's a ticking sound and possibly some distortion. this happened on both builds, until i limited the minimum Release with a resistor. i put either a 220k or 330k resistor before lug 1 of the 1M Release pot. bear in mind this will mean you can't get 0ms release time (which you proably wouldn't want anyway lol).

i also had to ground the input when bypassed, because that ticking would bleed into the bypassed signal. but imo, you shouldn't worry about all that until you know everything else is working.

does the actual circuit work by itself, without the switch? as in: input jack > board > output? or did it work before but not with the switch? it's best to take the switch out of the equation when debugging, imo.

it does get easier!! slightly...

[LoonDawg]

I did take the switch out of the equation for the debugging process but it is the bypassed signal that is now giving me problems.

I am close but I guess I'm not sure if the sound of the pedal itself is that great. There is a buzz but right now I think a lot of that is ground and switch issues so I will hold back until it is completely done.

The signal itself seems very distorted so I am worried that there is something off in the circuit causing it. I will keep going with the debugging of this stuff and hope that it is just bad connections of the alligator clips causing most of these issues. Thanks again

[GibsonGM]

That's why I don't like the darn Veros, man!  Much harder to diagnose, IMO.    Looks like MrStab has some good input, having built one...he's right, it gets easier, esp. after you learn how to read schematics and use the DMM a few times!    Your voltage-measuring looked to be ok, BTW.   

[MrStab]

good luck, Loon - let us know how it goes.

vero ftw! i think with your first few builds, you're trying to learn all these different areas of information as you work, but once the basics are out of the way, you'll find your mind has been freed up to figure out the ins & outs of specific circuits instead of getting caught up by details like grounding & switching. it took me a while to figure out schematics, but i'm glad i did.

[LoonDawg]

Well I got it all wired up correctly and the switch and leds work right.

There IS one problem though

It isn't a compression pedal, or at least it doesn't sound like one. The attack, release and threshold knobs as well as the treble switch don't seem to do anything at all. The Ratio and Level make the signal distort and overdrive my amp. I do have to admit that I kinda like it but I was hoping for a compression pedal and something I did along the way changed everything, or seemed to change everything about the pedal.

I am kind of at a loss, although it is pretty funny that I finally finished a pedal and it is completely different than I was going for.

Thoughts?

[LoonDawg]

Anyone? Not sure what to do at this point, maybe it's a lost cause and I just made an OD pedal with a few excess pots :-)

[midwayfair]

Read this and follow the instructions:
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Everyone is just guessing. You need to give us the right information, and enough of it, for us to diagnose the issue. There are standard rules to follow for a debugging, and often in compiling the information required you will either diagnose the issue or learn enough to find a similar issue next time. There are no substitutions for the steps listed in that link.

[LoonDawg]

To my knowledge, I've done all the applicable steps. Below is the link to all of the voltages on the veroboard layout but here it is again http://img59.imageshack.us/img59/8748/jfpf.jpg

I reread it and I think I've covered it all. The issue is that it isn't a compressor pedal anymore and I didn't make any part changes or anything so I am hoping someone might know what happened in the process. If not, it's ok. I will keep building, trying and learning.

Thanks

[midwayfair]

To my knowledge, I've done all the applicable steps. Below is the link to all of the voltages on the veroboard layout but here it is again http://img59.imageshack.us/img59/8748/jfpf.jpg

I reread it and I think I've covered it all. The issue is that it isn't a compressor pedal anymore and I didn't make any part changes or anything so I am hoping someone might know what happened in the process. If not, it's ok. I will keep building, trying and learning.

Thanks

Sorry, the picture wasn't loading for me. I didn't realize you already posted voltages.