Tubescreamer help

[adding_to_the_noise]

I just started building a tubescreamer from the Layout from Tonepad.com and i am having some problems. At first I thought i wasn't getting any signal but when i boosted the amp volume i could barely hear a somewhat distorted signal that breaks up a little bit. The only part substitutions i have made is a 47pf capacitor for the 51pf and 1n270 diodes for the 1N914s. Has anyone experienced these sort of problems with a tubescreamer build before or can offer me some advice for tracking down the problem? Any help would be greatly appreciated.

[oldrocker]

You might want to test voltages at the transistors and IC and display them here so R.G. or M. H. might be able to figure out whats going on with your circuit.  They can tell you what you need to try to debug and fix your TS.

[adding_to_the_noise]

Ok i will try to do that soon. Exactly how do i test the voltages? I.E. where do i put the leads from the multimeter to test the transistors and ICs?

[adding_to_the_noise]

ok here's the measurements:


1.What does it do, not do, and sound like? Bypass works correctly, circuit has signal but it is very week. I can barely hear it even with the amp turned up. Sometimes I hear a whistling/whining sound. The signal is distorted but it does not sound like it is continuous.

2.Name of the circuit =Tubescreamer TS-9

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? A 47pf cap for the 51, and 1N270s for the 1N014s but I do have some on hand if the 270s don't work correctly

6.Positive ground to negative ground conversion? N

7. What is the out of circuit battery voltage? => 8.42

Voltage at the circuit board end of the red battery lead =8.03
Voltage at the circuit board end of the black battery lead =.001


Q1
C =8.22
B =6.41
E =6.02

Q2
C=8.21
B=5.86
E=5.42

IC1 (or U1)
P1=  8.08
P2=  8.07
P3=Can't get proper reading—started at about 6 volts and counted down towards about 1 volt
P4=.001
P5=Pins 5,6,and 7 are experiencing the same problem as one-it will not give a static measurement, the voltage starts near 5 or 6 and steadily rises.
P6=
P7=
P8=7.4


D1
A (anode, the non-band end) =7.93
K (cathode, the banded end) =7.94

D2
A =7.93
K =7.93

D3
A =7.93
K =7.94

[Transmogrifox]

That really helps a lot that you used the "what to do when it doesn't work" sticky,  Two thumbs up, man 

Your problem is without a doubt related to U1:

IC1 (or U1)
P1=  8.08
P2=  8.07
P3=Can't get proper reading—started at about 6 volts and counted down towards about 1 volt
P4=.001
P5=Pins 5,6,and 7 are experiencing the same problem as one-it will not give a static measurement, the voltage starts near 5 or 6 and steadily rises.
P6=
P7=
P8=7.4

Here's what you should be reading:
IC1 (or U1)
P1=  4
P2=  4
P3=4
P4=.001  (OK)
P5= 4
P6= 4
P7= 4
P8=8

It should be very close to the values above.  Just to make sure we're using the same numbering system:
Viewing the chip as it sits in the circuit board (top up) with the notch or dot furthest from you, pin 1 is the top left, pin2 right below it...pin 4 bottom left, then straight across to pin 5 on the bottom right, 6 above...and pin 8 is the top right.

If you're referencing the pins correctly, then you have the power supply hooked up to the wrong pin. 

or...you have the chip in backward.  Does it get hot?  Does the battery voltage seem to go down quickly?

or...the cursed cold solder joint and things aren't in electical contact even though it appears that way.

or finally...you soldered the IC too hot and damaged it, or even ESD'd it before you even started.

The diode substitution is fine. 

The pinout can be found here:
http://www.tranzistoare.ro/datasheets/270/489253_DS.pdf

[adding_to_the_noise]

Well I'm still working from a breadboard so i don't think that soldering had anything to do with it. I've changed the chips once before but i don't think the first one was fried. Yes I am using the same numbering system for the IC as you are so I guess I'm stuck where i was before. Do you know anyways of testing if the IC is fried? Should I look for any certain signs?

[adding_to_the_noise]

Another Question: am I correct in placing pin 8, the one directly across from pin one, as the power supply?

[spudulike]

Pull the chip and check what your Vref or Vb is - should be ~4.5V.
The voltage decaying looks like a cap charging problem (particularly as the voltage on pins 5/6/7 is rising).
Pin 3 of the chip has a 1uF to Q1 emiiter resistor. Make sure you havent conected it to ground (ie the other side of the resistor).
Check the voltage readings at the chip pins with the chip out.
Pin 8 is indeed Vcc.

[adding_to_the_noise]

OK
1. VB is 7.7 so obviously there's a problem there-perhaps I should check the readings on my resistors again?

2. As far as the cap charging problem-what does that mean-do i need a new capacitor? And if I did how would I tell, I don't have a multimeter that can measure capacitance.

3. On the schematic the emitter resistor(10k) is connected to ground, unless you are talking about the 10k resistor that is connected to the other end of the cap that is connected to VB

4. I took the chip out and all the voltage readings were 0 except at 4 which was .001 and three which still displayed the decaying voltage problem

So I'm thinking about reworking my layout for the third time and testing all my resistors just to make sure.

[Transmogrifox]

Breadboard--
Make sure things are connected within the breadboard as you think. You can put the multimeter on ohms and stick little wires up from two holes that you think are connected to verify.  If it measures real low (like a wire) then you're good.

You are right in placing pin 8 as the power supply.  If it was truly connected that way, then it would have measured 8.something volts instead of 7.74 when other pins were measuring higher voltages.  Before you power up the circuit check these things with the meter set to ohms:

Pin 8 to where the battery + connection to the breadboard should be continuous (make sure power is not applied).
Pin 4 to battery minus should be continuous
Pin 1 to the resistor (pot) leads, and diode leads on that end
Pin 2 to the 47nF cap and to the diode leads on that end
The 10k/10k divider should have one end continuous to battery +, another end to battery -, and the center should be tested through to the components and pins it references on the schematic.

In the end, make sure every pin on the op amp is continuous to the parts you think they are, and not shorted to parts they shouldn't be.

Sometimes that "floating" voltage means that nothing is connected to the pin.  I'm guessing the problem was in your Vb divider.  If that was off, or floating, it would screw up both op amps and everything to do with that part of the circuit.

4. I took the chip out and all the voltage readings were 0 except at 4 which was .001 and three which still displayed the decaying voltage problem

Remove the capacitor at the Vb connection and see what the voltage is.  You can verify that much.  If it is fine without the cap, and putting the cap back in messes it up again, then get a different cap to put in there.

With the chip out, you should be measuring ~1/2 Vcc (about 4 Volts for an 8V measurement on the batt) on the connection pin 3.  Pin 8 connection should be the same as the power supply, and pin 4 at around 0 (0.001 ok). The rest of the pins locations may well give you funny readings like you described (and that would be ok since they're essentially floating without the op amp in there).. 

So I'm thinking about reworking my layout for the third time and testing all my resistors just to make sure.

good idea

[adding_to_the_noise]

Ok so I seem to be at a complete standstill. I can't get this thing to work! I rebreadboarded which delivered the correct voltages but no signal. Decided to try it again and now have no signal and incorrect voltages Along with my breadboarding skills apparently not being up to snuff, I can't figure out what is wrong with this thing. What do you guys do when you have breadboarded a few times and can't get it to work? Is there a way to test and see exactly which component or group of components is causing the problem?

[Transmogrifox]

Check out the Audio Probe on GEO.  It's a good tool to see where you're losing signal.

When you had the circuit with the correct voltages, did you check to see if your jacks were connected right?  Maybe you had the tip and ring backwards.  Verify that the ring (sleeve) connection is continuous to battery -, and the tip is connected to input/ output.

Are you also building the bypass circuitry onto the breadboard?

I know it takes a bunch of time, but it's worthwhile using the ohm meter (with the power disconnected) from resistor lead, to resistor lead to transistor lead to IC pin to capacitor lead, to pot pin....all the parts that are supposed to be connect.  Just do that to verify they are all connected. 

Next turn on the power and try it.

If it still doesn't work, then measure all the voltages and report as you did earlier.

If all the voltages seem ok, then you need to start stripping the circuit to the minimum just to verify each stage works sequentially to the end.  Start adding stuff as you verify the first part.

For instance, build the part with the input transistor buffer, and instead of connecting the capacitor to the 10k resistor on the input of the op amp, connect it to your audio jack just to make sure sound comes out.

The next step would be to get sound coming through the first op amp (clipping stage), then hook up the tone stage and see if you can get sound out of that.  Finally the output buffer and such.

This breaks the problem down into much more simple blocks to deal with

I hope that helps.

[adding_to_the_noise]

Thanks for the help, i was thinking about trying to break it down but wasn't sure how to do that. I built an audio probe last night and tried it out and it seems that the problem is with the IC. When I put the probe on Pin three of the IC there is signal, but then there is little or no signal on any of the other pins. I changed the IC and had the same problem, any suggestions?

[oldrocker]

This may sound like totally silly question.  But did you ground pin 4 for sure on U1?  The only reason I ask is that's how I tested mine and had the same result.  It most likely isn't the cause but you never know.

[adding_to_the_noise]

Yup it's grounded, but thanks for the suggestion could something after the IC be causing the problem? I've checked everything before and there is no problems so far.

[adding_to_the_noise]

Also, in the current build i'm testing, nearly all of the pins of the IC are registering close t 9V like they are just shorted to power and ground but i've checked and they're not.
Does anyone know the approximate transistor voltages for this circuit?

[Transmogrifox]

Holding the Multimeter negative lead on the batt (-), these are the approximate voltages you should be observing on the following:

Batt(+) = 9V

Q1
C =9
B =4
E =3.4
Q2
C=9
B=4
E=3.4

IC1 (or U1)
P1=  4.5
P2=  4.5
P3=4.5
P4=0
P5=4.5
P6=4.5
P7=4.5
P8=9


D1
A (anode, the non-band end) =4.5
K (cathode, the banded end) =4.5

D2
A =4.5
K =4.5

D3
A =4.5
K =4.5

Vb=4.5

Yes, Pin 4 *is* grounded.  I don't know your level of electronics knowlege, so I'll state something obvious here:
Make sure that EVERY part that has the ground symbol (triangle of lines) is connected to the battery (-) terminal.

If things vary by more than 20% from the above, then there's something pretty seriously wrong with how it's connected.

If the battery is fresh and right on about 9V, then things should be within 5% at most except for Q1 and Q2, in which case it depends on the transistor gain which may vary by more than 5%.

If the above measurements are not true, then you can be guaranteed it won't work, or it will sound bad at best.

[gaussmarkov]

fwiw, i have a verified breadboard layout for the tubescreamer on my layouts page.  just in case you decide to rip yours up again.

hang in there ... you'll get it to work.  you are getting great help. 

[adding_to_the_noise]

Ok so i've had some triumph as of late. The voltages are correct and I'm even getting signal all the way through the circuit; however, their is no distortion and the gain pot seems to have no effect on it at all. Any suggestions?

[Transmogrifox]

one guess:  look at the 4k7 resistor and .047uF cap.  One end (capacitor side)  is connected to the op amp pin 2 and the resistor side is connected to Vb.  You may also connect it to ground if you like.  Ensure this connection is good from pin2 through the cap, through the resistor, and terminating at the 10k/10k/47uF divider (or ground).  If this is not so, then that's your problem without a doubt.

The other guess is that pins 1 and 2 are somehow shorted.  Use your ohm meter to verify that you are not getting a low reading (like less than 10 ohms) between pins 1 and 2.

Either (or both) of those scenarios would produce the symptoms you have described.