need help for tubescreamer

[g.e.o]

hello people. i just finished one more effort to fix the problem i got with my tubesreamer 808 project from tonepad.com. my problem is that i have no distortion at all and the drive pot doesnt work. i checked all of my solderings and they r perfect. also checked all the previous messages in this forum and saw some advices that i also checked and still nothin. to make it easier to u, the bypass switch is made fine, so r the parts placed on the pcb and the only modifications i made are the 51pF cap (put a 47pF) and the drive pot instead of 500k is 470k because i couldnt find neither of them. i read in the forum that changin the cap is not a problem at all. so please someone help out with this. i also did all the measurements and they are correct accordin to what i read in the forum and some other sites. thanx in advance.

[jonathan perez]

hello people. i just finished one more effort to fiz the problem i got with my tubesreamer 808 project from tonepad.com. my problem is that i have no distortion at all and the drive pot doesnt work. i checked all of my solderings and they r perfect. also checked all the previous messages in this forum and saw some advices that i also checked and still nothin. to make it easier to u, the bypass switch is made fine, so r the parts placed on the pcb and the only modifications i made are the 51pF cap (put a 47pF) and the drive pot instead of 500k is 470k because i couldnt find neither of them. i read in the forum that changin the cap is not a problem at all. so please someone help out with this. i also did all the measurements and they are correct accordin to what i read in the forum and some other sites. thanx in advance.

^^^^^^^^^^^^^^^^^^^^
does that answer your question? hahaha

[g.e.o]

not really. so can u help me out?

[QSQCaito]

Firssssssssssst of all, hello:P

Have you read the post that has a sticki at the top? the one of what to do when it doesn't work? read it..
http://www.diystompboxes.com/smfforum/index.php?topic=29816.0
second.. u haven't done all ok, if not it should be working

third, test your drive pot..

four, we need more infooo, read that post, and make a detailed decease certificate:P

five, bye bye

dac

hope it helped for something

[Aharon]

Those changes you made do not make a significant diference,your unit should work.............so you have to  look for that ellusive mistake we all make sometimes.
Look for solder blobs,wrong value parts etc.
Aharon

[g.e.o]

ok. here is the form with the measurements

1.What does it do, not do, and sound like? no distortion at all and drive pot doesnt respond
2.Name of the circuit = ts 808
3.Source of the circuit (URL of schematic or project) = tonepad.com
4.Any modifications to the circuit? Yes
5.Any parts substitutions? instead of 51pF cap i used 47pF and instead of 500k log pot i used 470k log
6.Positive ground to negative ground conversion? no
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => 9,20 V
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead = 9,20 V
Voltage at the circuit board end of the black battery lead = 0,07 V

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1
C=9,0V
B=3,6V
E=3,1V

Q2
C=9,0V
B=3,6V
E=3,1V

IC1 (or U1)
P1=4,8V
P2=4,5V
P3=4,5V
P4=0,0V
P5=4,8V
P6=4,8V
P7=4,8V
P8=9,0V

D1
A (anode, the non-band end) =4,5V
K (cathode, the banded end)  =4,4V

D2
A =4,4V
K =4,5V

Also checked my drive pot and when its connected on the circuit it says 390k but when its not it says 470k as it is. of course with it set to the max. i dont know if that helps. PLS help!

[petemoore]

 Somewhere in links I think there's a page about biasing and wiring up opamps...GEO has transistor biasing information
Q1
C =3,1V   
B =3,6V
E =9,0V
  I suspect possible misorientation [upsie down?] or something's not letting the transistor bias. I m guessinig from memorey [link schematic you used? always helps] that this is a buffer, and that the Collector is what...connected to V+ which is 9v. Q1 is where I'd start.
Q2
C=9,0V
B=3,6V
E=3,1V
  I'm not real good debuggin' buffers cause my buffers always worked, IIRC this too is a buffer, Collector looks good @ 9v, and the base/emitter voltages are probably close to operational bias...not too sure...you'll have to figure that out for me or use an audio probe, the output [E] on a buffer should sound the same, very close to 1/1 [unity] as the input .
IC1 (or U1)
P1=4,8V
P2=4,5V
P3=4,5V
P4=0,0V
P5=4,8V
P6=4,8V
P7=4,8V
P8=9,0V
  These actually look pretty good!, all the inputs and the output for each OA is around 1/2v, ground is made at pin 4 and P8 says 9v...looks good
  I would start with the first transistors debugging, re-verify the pinout using the data sheet, also you could remove power and measure the biasing resistors around Q1, *if you get a lower than marked reading...
*  tell me
*  disregard if 
  /figure out if there's a way through for current to flow through the circuit other than through that resistor, looking at the schematic
  *Do the math and calculate if that resistor and alternate current path jibe with the circuit equation it creates
  *[I Very rarely] pull one end of the resistor and re-measure it, any alternate circuit paths are eliminated when one end's pulled out.
  did you use a PCB or what 's it built on?
  Use the DMM and test resistances, also to verify connections/non connections...dogmatically following through circuit and schematic to veryify everything is as it should be, and nothing further is...no 'extra' connections.
  It appears you have a board with no in/out switches and jacks [good, this makes debugging and preserving wires better, plus lessens the chance of shorting/burning].
  I built a test/jig, it's just two jacks grounded, ground wire extends to a testclip, each tip of the mono jacks terminates to a testclip. this is installed in a RACO large, on top of that is cardboard ['tray'] with the wires to testclips through it...I can then connect the guitar and amp with cables to the proper jacks [for input and output] clip the ground to the circuits ground, the in wire from input jack clipsto input of the circuit, same with the output to amp...quick and EZ to get setup...

[g.e.o]

hello pete and thanx for helping me out. well i dont think its the transistors coz that doesnt have anything to do with the clipping stage as far as i read. my problem is that i get all the other functions right but i have no distortion and the drive pot is like not workin at all. from what i read here i must have a problem with the feedback network but i dont know how to test it. yes i am usin a pcb and i have done the same thing as u for connectin the guitar/amp and be able to test it. also tested the resistors before placing them on the pcb and all the measurements are correct. i do that anyway coz many times i found problems in resistors. dont know what else information to give u so that i can help. sorry. my knowledge is limited.

[petemoore]

   you can use an audio probe to test what's up here and there in the circuit.
  The resistance int he feedback loop [output and -input of the clipping OA], can be measured hook the DMM up to the pot connecitons and twist the pot.

[Transmogrifox]

well i dont think its the transistors coz that doesnt have anything to do with the clipping stage as far as i read. my problem is that i get all the other functions right but i have no distortion and the drive pot is like not workin at all.

Don't be too quick to rule out the transistor.  My guess is that you had:
Q1:
C 9.0
B 3.6
E 3.1

Because I don't think a transistor would bias up so nicely if it was actually in backward.  I would say that report was merely a naming error.

Anyway you should audio probe the circuit.  If there is something that is blocking input signal on the input, then the high gain of the TS may simply be amplifying the bleed-through and it sounds undistorted because you're merely recovering a really quiet input.

Per our PM discussions, I, like you, am pretty convinced the problem lives somewhere in the drive stage.  I hope you're able to root it out without too much further frustration.

[twabelljr]

     Looking at D1 and D2 voltages, it seems that the diodes are not facing in opposite direction of each other. D1's anode voltage should be the same as D2's cathode voltage, and D2's anode the same as D1's cathode

D1
A (anode, the non-band end) =4,5V
K (cathode, the banded end)  =4,7V

D2
A =4,5V
K =4,7V

It seems that if this is the case, one half of the waveform would be severely clipped and the other unaffected. I don't know what that would sound like, but it should probably be looked into. Also you could remove the gain pot and insert a 470k or 1 meg resistor from terminals 2 to 3 for max gain.

[g.e.o]

well 1st thanx alot for the help guys! i made a mistake which i already corrected now at the Q1 and Q2 measurements. Transmogrifox was right. as it comes for the diodes i'll check it again but according to previous posts in the forum it must be ok. but what u said twabelljr sounds reasonable so i'll give it a try. thanx again.

[g.e.o]

replaced the diodes with some new and the new measurements are written above to my previous post with all the other measurements.

[g.e.o]

ok. here we go. thanx really a lot everyone who helped me through this. audio probe REALLY RULES!!!! found the problem in a second! it was a stupid cap that had a problem from the factory. never believed it could be something like that. just replaced it and......YEY, it works! COOL! am very excited! thanx a lot again and i will keep on reading the stuff here and try to help as well if i can. promise! take care guys. talk to u soon!

[petemoore]

   
  It's always 'something' ..It seems You've developed the ability to find the 'thing' in this case !!

[hubble]

audio probe REALLY RULES!!!!

got that right!

[g.e.o]

indeed pete! i think i begin to learn something in here  thanx to u people.  its not that difficult after all but need patience and clean mind as i've been adviced b4. also sometimes its not ur fault but somebody elses that gives u a damaged part. in my case for now thats it but i guess i always have to  find whats wrong no matter who's fault it is. still its wonderful when u hear it play! u feel proud for ur self. so do i right now but u guys should feel much more proud coz u give help and exchange knowledge which in our days is not easy to be found. i guess this is the good side of the internet but it wouldnt exist if there were not nice people like u! thanx for once more!