First Time Tube Screamer - No Audio - Debug Info. Please help!

[pgorey]

Hello all!  I wish my first post here was a triumphant "I powered up and it worked first try!" but alas, I powered up my first TS-808 clone and my bypass switching and LED are working great.  Nothing else though.  Please see my debugging stats below and thank you in advance for any help you can provide.  I'm so thankful for sites / forums like this.  I built my first Fuzz and am finishing decals next week and was so inspired by that success that I caught the bug so to speak and want to build a complete pedal board of some of my favorites by scratch.  The TS-808 is such a simple circuit that I felt a little deflated when it didn't work out.  Happy to post photos or links in addition to this info or take measurements anywhere else.  I have checked all cap and resistor values again just to be sure my eyes weren't playing tricks  - swapping the 1k and 10k resistors could be an easy mistake but I'm 100% sure on those.  Anyway, thanks again and I'm looking forward to getting this thing to work! 


1.What does it do, not do, and sound like?

When in bypass mode using a 3p3t foot-switch with the wiring diagram used at the end of this thread (http://www.madbeanpedals.com/tutorials/downloads/MBP_FootswitchWiring.pdf), the status led turns off and the guitar can be heard clean through the bypass switching.

When the switch is turned on, the led lights up and all sound is muted. 

2.Name of the circuit = Tonepad Tube Screamer TS-808 with asymmetrical diode configuration.

3.Source of the circuit (URL of schematic or project) = http://www.tonepad.com/getFile.asp?id=81

4.Any modifications to the circuit? N

5.Any parts substitutions? N

6.Positive ground to negative ground conversion? N

7. What is the out of circuit battery voltage? => 9.12

Voltage at the circuit board end of the red battery lead = 8.99
Voltage at the circuit board end of the black battery lead = 0

Report the voltages as follows:

Q1
C =8.84
B =3.28
E =2.79

Q2
C=8.83
B=4.16
E=3.95

IC1 (or U1)
P1 4.35
P2 4.35
P3 4.35
P4 0
P5 4.35
P6 4.35
P7 4.35
P8 8.77

D1
A (anode, the non-band end) =4.34
K (cathode, the banded end) = 4.34

D2
A =4.34
K =4.34

D3
A =4.34
K =4.34

For extra credit, while you're waiting for someone to tell you what they see, probe the pins of each of the electrolytic caps, verifying that the voltage on the (+) pin is more positive than the voltage on the (-) pin. If it's not, that cap will eventually fail, whether it's the immediate cause of the thing not working or not.

All polarities good on electro caps 0 on negative side for both.  4.34 on 47mf positive pin and 3.86 on 10mf positive pin

[duck_arse]

hello pgorey, and welcome, and we want those photos, please. your opamp looks happy for voltage, so I'd guess off-board wiring error. and we all love those, don't we?

also - if your Vb voltage is 4V35 (as shown at the IC pins), and the base voltage of Q2 really is 4V16, then the base current is only 372nA, and I don't think the transistor gain will be high enough to allow this. can you remeasure and confirm the voltages around Q2? and your Vb voltage?

but don't quote me.

[pgorey]

Thanks for the quick response Duck!  I will post photos and measurements tonight after the wife and kiddo go to sleep.  I feared the off board electronics could be the issue mostly just because of the amount of jumper soldering and wire trimming required to remove it / re-do it but I'll look back over everything again to make sure there are no issues with the wiring at the switch, battery connector and board.  Perhaps there is a loose soldering point between the board and jack in / out / switch.  Also, I'm waiting for a 2.1mm power socket to arrive to solder that on as I'm not interested in using batteries but have a battery clip in use until then.
Some additional info before I get home:  I'm using a green led that calls for a minimum resistor value of 230ohm - I'm using a 330ohm resistor.  I don't think this should be an issue but it's more info just in case.  Thanks again. I should have all the photos and measurements up by 10pm eastern time. 

[GibsonGM]

Hi PGorey, welcome!

Your LED resistor is not an issue - in fact, it could most likely be a larger value!  Do not go lower than the suggested value, however, or it may burn out.

What I do to assure myself the problems are in offboard wiring, is to connect my PCB to input and output jacks (AND ground both) and play my guitar through it before I install the switch and the power jack.    If any issue arises after then it is most likely in those 2 areas!!     

And after it is placed in the enclosure, if there is an issue, then I can reasonably think it may be a short to the enclosure, a ground not making contact, or a part has bent and touched another part - something like that.  It is good to eliminate the PCB as soon as you are done with it.   Plus, you get to play it right away for a little while      That is just what I do, your method may vary. 

Good luck, you are probably close to a solution, and Duck is a good one to help you through it!

[pgorey]

Thanks Gibson!  Yes, I should verify with just the jacks first.  Patience is not strong with me when it comes to soldering and building in general so I just threw it all together thinking that it would surely work like the Fuzz I started with.  Pretty foolish I know.  Now i will spend double the time to take apart what I have just to verify the PCB and then put it all together and then put into an enclosure. My process for finishing the enclosure has been strange too as I like to stuff the enclosure first to get my knob, switch, power and LED placement practically laid out and then take it all out to drill and then design the decal around it.  I'll then install everything again and cut / place a paper version of the decal over to be sure before I remove everything, drill, decal, seal and sand.  Then I stuff it again.     Goofy but it helps be to be absolutely sure about placement and drilling before tear up the enclosure.  Anyway, lesson learned for the next round regarding the off-board parts. Really appreciate the knowledge on this forum!  I have been reading other posts and am getting so inspired and pumped to keep building.

[GibsonGM]

Don't worry, in just a little time this will become much easier for you.  Keep up the good work! 

[pgorey]

Alright.  Below is a link to pics via google drive.  Please let me know if you'd like to see anything else. 
https://drive.google.com/open?id=0B1g5e1cgIzbCaXppaXZsSWVfSm8

I have verified all resistor values as well as switch wiring.  I have clean solder points on the switch lungs, no shorts on the board or anywhere else I can see.  Please don't judge me on the soldering too harshly - I had a couple pads pull up so made some quick jumpers.  One thing could be amiss with the pots.  Can someone confirm I have the correct lugs hooked up?  I think I did it correctly.  You can see nearly everything in the pics except for pot values and they are as specified. One resistor is hidden in the pics under D1.  Green, Brown, Orange, Gold = 51k as specified.

My Q2 values are as follows per the spec sheet layout at the link below and I have confirmed proper placement on the board.  My battery is currently running at 8.59v.  I unfortunately don't have another battery to use until tomorrow.

http://www.interfacebus.com/semiconductor-transistor-packages-TO-92.html

E:  2.97v
B:  3.46v
C:  8.5v

At the IC, Pins 1-3,5-7 measure at 4.21v
Pin 4=0
Pin 8=8.5v

[GibsonGM]

You have removed the switch and are using input/output jacks, Pgorey?   

I don't see anything VERY wrong with your soldering, perhaps some cold joints...you may wish to reflow the ones that look gray and not silver.   

If you feel up to it, you could try making an AUDIO PROBE...(search, easy to build).  It could tell you where your problem lies...

[pgorey]

Sheepishly replies - no, I have not removed the switch but will   I just put all the soldering toys away for the night but may fire them back up after everyone goes to bed.  I did try to clean up all points earlier but will tap them again to get a bit more shine on the dull ones.  Since my battery is below 9v I will also solder up a quick 9volt supply to snap just to make things easier / more consistent until I receive the power connector.

I will also build an audio probe since it seems like a practical tool to have.

[pgorey]

Here's a link to updated pics of the board.  I checked all soldering again and tried to get rid of any visible cold solder joints / make everything shiny.  I think it loos good but please let me know if anything stands out.  Since I don't have the parts to wire up an audio test probe or power supply without butchering one of my PS, I removed the switch and just have the mono I/O jacks wired to test out the circuit with battery.

Just verifying that this wiring is correct:

Tip on input jack goes to circuit input.  Ground on input goes to ground on circuit and is tied together with the ground of the 9v battery lead as well as ground on the output.

Tip on output goes to circuit output. 

What happens is that I now have audio without a bypass so something on the circuit is working.  I verified that the tone circuit as well as output is working.  Unfortunately, no drive.  Can anyone see any issue with my drive pot?  I think the diodes are correctly oriented.  Any other thoughts on on what I'm missing?

[pgorey]

Here's the new pics:

https://drive.google.com/open?id=0B1g5e1cgIzbCaGxEaXB2VWhsUUE

[duck_arse]

erm, well, I can't see nuttin, cause good old googoo don't support my browser. but I can say your new transistor voltages for Q2 look much better.

[GibsonGM]

I think you need to audio probe!  Taking a look at things sometimes works (often, if you have a wrong-value part or bad solder joints), but there is a time when you just WANT to know where the problem lies!    So you make the quick, easy probe, and follow the signal path in. 

Are your diodes in the circuit the right way?   I would trace each pot wire, as well, to be sure it is going where it should.   Esp. the drive pot. 

Can your read a schematic, P?

[pgorey]

Thanks Gibson.  I will definitely build an audio probe once I can pick up the parts locally.  I don't want to hack up a cable and would prefer to build a decent one but I agree that following the signal with that type of tool would be really helpful.  Since I'm so new to this, I can't say for sure that the diodes are in the right order, but based on Tonepad's PCB and my somewhat reasonable ability to read a schematic / google search , I think they're in the right order.  Wiring appears to be right on the pots compared to their drawings seen here:

http://www.tonepad.com/getFile.asp?id=81

Duck, I'm trying to get photos up onto DIYstomp's photo gallery but it's slow.  Anywhere else I can post that you can see?

[duck_arse]

imgur still works this end.

[pgorey]

Never used imgur before but yeah, that's about as easy as it can be!

http://imgur.com/a/qtd2f

[duck_arse]

Ra should be 100R, what value do you have fitted?

also, what's that black gunk on the resistors? also also - those diodes! where did you get them, why are you using them?

[GibsonGM]

Ra should be 100R, what value do you have fitted?

also, what's that black gunk on the resistors? also also - those diodes! where did you get them, why are you using them?

Ha ha, I noticed that too - thought they came in the kit?  Or was it just the PCB you got?

[pgorey]

Oh man.  I had a 100k resistor in the Ra position - shaking my head as I had checked them a few times but just read the schematic / layout wrong and assumed 100k instead of 100.  Let me find a 100 and swap it in.  I feel silly...

I ordered the GE 1N91 NOS Germanium Power Diodes from Small Bear. Wrong diodes?  I would certainly appreciate soldering something smaller!  This is the small bear link:

http://smallbear-electronics.mybigcommerce.com/1n91-nos-germanium-power-diode-ge/

One other thing I just noticed from reviewing the pots in my order history is that they are all Alpha 16mm Single-Gang, Reverse Audio & "W" models.  Is that an issue? If I'm remembering correctly, I think I ordered off of a parts list for the tonepad board from small bear's parts list library but now I can't find that list in their library even though the pcb purchase page links to it as you can see below...strange.  I'm almost 100% sure i had an xls file as I had one in my Excel "recents" list called TS but i have unfortunately since deleted.  Woops.

http://smallbear-electronics.mybigcommerce.com/pcb-tonepad-tube-screamer/
http://diy.smallbearelec.com/Library/PartsLists/PartsLists.html

I also built the Keen "improved" audio probe and even after watching videos, I'm a bit confused as to how to use his model.
His drawing is here:

http://imgur.com/0o2wfjj

And my soldered up version is here:

http://imgur.com/a/HDN9G

The black gunk on the resistors is some electrical tape goo.  I have a small pair of needle nose that I wrapped in electrical tape to make them softer on holding some components without scratching etc. - in this case the adjacent transistors when soldering on.

[pgorey]

Figured out the audio probe.  What a great simple idea / tool!

This link shows a picture of the board and pots and where the issues are:

http://imgur.com/a/43Im9

The pins marked in blue are showing no audio just at those pins.

The pins marked in red are showing components that have no audio on either side.

Does anyone have any quick insight?

I changed out that 100k to 100 before testing.