soldered Tube Screamer: it doesn't work.

[moeburn]

Hey guys, I'm using a modified version of the tube screamer.  Everything is the same from this schematic:
http://www.generalguitargadgets.com/diagrams/ts-808_sc.gif
except I used the drive circuit between pins 1 and 2 from this schematic:
http://www.greene-pedals.com/pdf/scrmr.pdf

I know it works because I built it on the breadboard.  

(from the sticky)
1.What does it do, not do, and sound like?  It does not make any sound.  I have the amp hooked up to the output, the guitar to the input.  When I plug the battery in, i get a low 'pop', but there is no sound, not even when i sweep the pots to all their ranges.
2.Name of the circuit = Tube Screamer
5.Any parts substitutions? If yes, list them.  The drive circuit between pins one and two.  For the diodes i have two wires leading off to a 16 pin IC socket (one wire goes to left 8 pins, other wire to right , so i can change diodes easily.  
I also have a little green LED w/1Kohm so I can immediately know if there is a ground-hot short.  Which there isnt.  The LED works fine when power is on.
6.Positive ground to negative ground conversion? Y or N no.

*edited* Voltage readings:

V+ = 9.3
VR = 4.6
GND = 0

Q1
C = 9.3
B = 2.6
E = 3.0

Q2
C= 9.3
B= 4.0
E= 3.7

IC1 (or U1)
P1 - 4.6
P2 - 4.6
P3 - 4.4
P4 - 0
P5 - 4.6
P6 - 4.6
P7 - 4.6
P8 - 9.3

Diode rail: 4.6v both sides.

Any help is greatly appreciated!

Edit: Fixed VR

[moeburn]

Update: Ok i fixed the VR problem, it had a short to V+.  All my voltage readings are now perfect as described in build instructions.

I'm getting >2Mohm resistance (my meter won't go higher) around the 0.2uF input cap, C1.  I don't know how to test to see if caps are dead or not.  I tested other electrolytic caps, they have low climbing resistance.  I tested other film caps, they all have 100% resistance.  How do I know if C1 is dead?

[Connoisseur of Distortion]

capacitance meter  :wink:

there's a DIY thing for a cap meter around here somewhere...

[moeburn]

Well yeah but that would mean another trip downtown to get the parts to build another circuit to fix this one.  I could just buy another .02uF cap there.

Does anyone know how to see if film/ceramic caps are open or not?

[ibanezts808]

your transistors aren't biased if I'm correct.  the collectors should only read about 4.5v

[moeburn]

your transistors aren't biased if I'm correct.  the collectors should only read about 4.5v

OK I fixed that problem, the VR shorted.  Here's the new readings:

*edited* Voltage readings:

V+ = 9.3
VR = 4.6
GND = 0

Q1
C = 9.3
B = 2.6
E = 3.0

Q2
C= 9.3
B= 4.0
E= 3.7

IC1 (or U1)
P1 - 4.6
P2 - 4.6
P3 - 4.4
P4 - 0
P5 - 4.6
P6 - 4.6
P7 - 4.6
P8 - 9.3

Diode rail: 4.6v both sides.

PLUS i even tried replacing my C1 input cap with another one (because i was getting infinite resistance between input and Q1 base), didnt work.  I tried replacing C1 with a jumper, STILL doesn't work.  My voltages are perfect and I'm still getting NO sound out of the amp other than the pop when i turn it on.

I forgot to mention I'm using an LM386 instead of the 4558.  It has also worked on the breadboard layout.  Would I still be getting these correct voltages even if I had a faulty chip or transistors?

[vanhansen]

Um, the LM386 is different than the 4558 pinout wise, isn't it?  I've never seen anyone use an LM386 in a Tube Screamer circuit, it's more of a low power power amp, a.k.a. ROG Ruby and Little Gem.

[moeburn]

Um, the LM386 is different than the 4558 pinout wise, isn't it?  I've never seen anyone use an LM386 in a Tube Screamer circuit, it's more of a low power power amp, a.k.a. ROG Ruby and Little Gem.

Sorry, thats happened before.  I keep mixing up the LM386 with the LM358.  The LM358 works fine on the breadboard.

To make things simpler, I built an audio probe and tested it.  Hooked the hot lead of the probe to Q1 base - audio is fine.  Hooked it up to Q1 emitter - no audio, silent.  Voltages are still fine.  I pulled the transistor (it's socketed) and put it in my hFE meter, in the proper orientation, it read 256.  The transistor is fine, and in the right orientation (2SC1815).

Update: according to my meter, Q1 has the following voltages:
C - 9.3
B - 0
E - 0

The only voltage for B is the 510k going to VR.  Yeah, you're only gonna get about 100mv after that big resistor.  But it should be 3.3 and 3.0.

[vanhansen]

Sounds like a biasing issue around Q1 somewhere.  On GGG, this is what the voltages say for Q1 and Q2 using 8.8v:

Q1
Collector 8.8
Base 3.5
Emitter 3.0

Q2
Collector 8.8
Base 3.5
Emitter 3.0

What looks off too much is the base voltage on Q1.  The collector and emitter look fine.

[moeburn]

For some reason my base and emitter on Q1 have dropped to 0v since i've been troubleshooting it.  As far as I can see, its all wired and soldered fine.  

edit: Ok the base and emitter on Q1 are the same voltages i said before, when input is unplugged.  If I plug something into input, B and E drop to 0.  Regardless of the cable I'm using.  Any explanation?

[vanhansen]

Check the wires coming from the input jack to the input of the circuit.  If you're using a stereo jack at the input, tip top circuit input, ring to battery negative, sleeve to ground.  That's the only thing I can think of.

[moeburn]

The wiring is fine, and i'm using mono jacks at both ends.  Does anyone else have different voltages when something is plugged in?  I've triple checked all my wiring everywhere.  Apart from the biasing resistors being a few k off (resulting in about 1v off), everything is perfect.

The input jack wiring has to be working, cause if it wasn't, i wouldn't be hearing any audio with the audio probe.  I don't hear anything from the emitter of Q1, and thus nothing else has audio.  Not even with different transistors, in different pin orders.

I did, however, try putting a jumper between B and E, and this worked 'sorta' fine, I got audio at the other end of course it sounded really crappy.

[moeburn]

Ok now i'm really frustrated.  The circuit works when there is no input plugged in.  Q1's B and E short when input is plugged in.

[vanhansen]

<scratching forehead>....that is bizarre.  So if you have the probe hooked up to the Emitter, and no jack is plugged in, you hear sound?  What if you put the probe at the beginning of the input without a plug in the jack, do you still hear sound?  How about with a plug in the jack, probe at the input?

Just trying to come up with some other troubleshooting ideas and hopefully nail the problem.

[moeburn]

<scratching forehead>....that is bizarre.  So if you have the probe hooked up to the Emitter, and no jack is plugged in, you hear sound?  What if you put the probe at the beginning of the input without a plug in the jack, do you still hear sound?  How about with a plug in the jack, probe at the input?

Just trying to come up with some other troubleshooting ideas and hopefully nail the problem.

I fixed that now, my 1/4" to 1/8" adapter was shorting it.  And I had the whole thing working.  So I brought it to my guitar to test it, and it didn't work, and now my voltage divider is giving 1.5v instead of 4.5v.  I'm thinking i'll just build one seperately.

[vanhansen]

Glad that problem is out of the way.  As long as you get the VRef to 4.5v you should be good to go.

[moeburn]

Glad that problem is out of the way.  As long as you get the VRef to 4.5v you should be good to go.

Since i'm not doing this tonight, I have a quick question for anticipation purposes.  If my Vr wasn't grounded, would i get any sound?  If it was only 1.5v?

[vanhansen]

Glad that problem is out of the way.  As long as you get the VRef to 4.5v you should be good to go.

Since i'm not doing this tonight, I have a quick question for anticipation purposes.  If my Vr wasn't grounded, would i get any sound?  If it was only 1.5v?

I don't have an exact answer on that.  Hopefully someone else can chime in with a definite on that.

[moeburn]

All right, now I'm stuck once again.  I get loud highpitched noises along with random pops and silences when I plug it in, however, I've redone the soldering on the board a few dozen times and it still looks good.

I rebuilt the voltage divider on a seperate board.  A 10k from V+ goes to Vr, and Vr goes to ground via another 10k and 47uF in parallel, just like the schematic.  I wired it to the main board.  No matter what I do, it is only giving 1.7v from the 10k resistor, I even used different components (same values, but different manufacturer).  What the heck is going on?

I'm reluctant to just put a couple trimpots in the voltage divider to get 4.5v, up from the 1.7v, since my problem might be somewhere else.  If I can't get this fixed before I get all my PCB stuff, I'm just gonna take it all apart and pcb it.

[moeburn]

Ok I got Vref to 4.5v using a trimpot, but the two values of the resistors weren't equal.  I was using a ratio far greater than 1:1 for the dividing resistors to get half the supply (9v) voltage.  Whats going on?!