TS808 Tube Screamer Project... No sound... Please help

[radiancephil]

Hello, first I would like to inform everyone here that I am a total noobie in building effect pedals... My problem here is that my TS808 which I built has no sound... The bypass works... Otherwise, it has no sound... Everything seems fine to me, no cold solder joints or whatsoever... Took me a few days of debugging to realise the problem with transistor EBC and ECB pin difference in different transistors...

1.What does it do, not do, and sound like?
   Only works in bypass... Otherwise, no sound

2.Name of the circuit =
     TS808 Tube Screamer

3.Source of the circuit (URL of schematic or project) =
    General Guitar Gadgets

4.Any modifications to the circuit? Y or N
   Yes... I added a 3rd diode in place of a jumper for the assymmetric clipping modification based on GGG's. 

5.Any parts substitutions? If yes, list them.
    Yes... I used C1815GR capacitors... Instead of the 510k resistor, I used 516k resistor due to stock availability. I used cheap pots (B20K, B500K and B100K) due to stock availability too... Despite all these substitutions, it should still at least have some sound right?

6.Positive ground to negative ground conversion? Y or N
     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? =>
     8.8V

IC (RC4558P)
P1: 4.0V
P2: 4.4V
P3: 3.7V
P4: 0V
P5: 3.8V
P6: 3.8V
P7: 3.5V
P8: 8.3V

Q1
C: 8.4V
B: 1.1V
E: 2.9V

Q2
C: 8.4V
B: 1.1V
E: 2.9V

D1
A: 4.4V
K: 3.8V

D2
A: 3.6V
K: 4.4V

D3
A: 3.6V
K: 3.5V

D4 (LED)
Flag: 0V
Pole: 1.9V

Before this, I soldered the pins of the transistors wrongly due to the different pin layouts of different transistors... My transistor readings are a lil weird, could it be because I fried it earlier when I soldered them wrongly??? Please help me with my problem here... I have spent a total of almost 10 hours in the past 3 days trying to find out whats wrong with it...

Can someone also teach me how to upload a photo for me to show you my circuit???

[Arfman]

Does your multi-meter have a diode checker (usually the lowest setting on your ohm meter...have a little picture of a diode or something)...

If it does, pull the transistors. Put your red lead on the base. Then check both the collector and emitter with the black lead. You should get a small reading, which is bascially the voltage drop...

Then reverse it with the black lead in the center. You should get nothing measuring from the collector or emitter...

Your base voltage should not be lower than your emitter voltage...

[radiancephil]

Do I have to plug in the battery and turn it on with everything plugged in to this transistor test you've just mentioned???

[Arfman]

Do I have to plug in the battery and turn it on with everything plugged in to this transistor test you've just mentioned???

No...ideally you should pull the transistors out...

[radiancephil]

Can you teach me how to post pictures online??? I want to show you a picture of my board and my analog multitester... Then you can tell me if my meter has the transistor checker function...

[johngreene]

Your transistors are probably fried. Either that or you still have them in wrong. The emitters should not be higher in voltage than the base. The board is layed out for a 2n3904, EBC style transistor. If you put a 2SC1815 in there you would have tied the base to +9V which could have done some damage.

You could remove the transistors and put a cap from Base to Emitter and see if it works. If it does, then you know the transistors are the problem. The 10k emitter resistor and 10k pullup on the input to the opamp will severely load down the input so it won't sound right until you get good trannies in there.

--john

[radiancephil]

Sorry for the noobie questions, but in your sentence "You could remove the transistors and put a cap from Base to Emitter and see if it works.".... What does "cap" mean??? Do you mean capacitor??? If yes, what rating???

[johngreene]

yes, 'cap' means capacitor and anything from .1uF to 10uF would serve the purpose of debugging. You could probably even forget the cap and just short the base to the emitter. The 510K resistor for base bias will limit the current enough to prevent the 4.5V from being loaded down.

Just remember the input impedance is going to be really low (<5K) so it will not work very well with guitar pickups. However, there should be enough gain in the opamp to tell if everything else is more or less 'working'.

--john

[GREEN FUZ]

To upload pictures you need to first find a picture hosting site. There are many but the one I`ve been using is http://photobucket.com/register.php?ref=login

Sign up for free, upload pictures from your computer then copy the IMG code and paste into your post. Baddabing.

[radiancephil]

My ts8708 finally works and it sounds great... Thank you everyone for all your help and support... I made an audio probe and it is so damn useful...