Tube Screamer clone not working

[caspercody]

The pcb layout is for EBC pin format, not for the 2SC1815 layout. You need to twist the legs around to get this format. See the instructions at the GGG web site.

[caspercody]

Also, the instructions tell you what voltage you should have at certain points.

[64fx]

Thanks guys!

I've got a 3.9k resistor (I think) on the LED, so that should be OK.

The switch is oriented the right way.

I thought Pin 4 was going to be 0, but it stopped on .1,  I can check that reading again because I may have done something weird there.

Caspercody, you say the pin layout is EBC, is that top to bottom with the Emitter being on top?  If so, that may be my problem.  From what I could tell I thought it was CBE.  Hopefully, that's it.  I'll try that, and let ya'll know what I find.

Thanks again for taking time to help!
Daniel

[caspercody]

I do not have my build in front of me, but I did build this pedal and used the 2sc1815 transistor. I had to bend two of the leads around, meaning the middle was on the outside and the outside was now in the middle positions. I bought my transistors from Mouser and got the data sheet for the one I bought and compared it to the layout. Just look at the schematic to verify where the ECB points compare to the pcb layout, and verify with the data sheet that the leads line up. I had no problems with this pcb and layout so I know it works, and works great. I also added sockets to the common mod components so I could swap parts easy.

Good luck

[The French connection]

Yes, if you use 2sc1815 you got to criss-cross the middle leg with the leg at the right when facing the writing side...dunno if it's clear! But anyway you must have 0V on pin4...Did your led light on when activated? You know, a picture is worth a thousand words.

Good luck!

Dan

[64fx]

Thanks Dan!

I'll take a look at mine and see how I've got it in the pcb.  Just to make sure, looking at the board top to bottom, it should be ECB right?  I'll check the pin 4 voltage again too.

The LED did not light.  I can't remember for sure the value of the resistor I put on it, so I'll double check to make sure it's around 4k-5k.

Would it help if I posted a picture of my build?

d

[The French connection]

Just to make sure, looking at the board top to bottom, it should be ECB right?  I'll check the pin 4 voltage again too

Nope! The layout is designed for transistors with a "EBC" pin format. If you use the 2SC1815 you'll have to twist the middle pin out to the side to get it to fit. If your Led did not light, your switch is miswired or you have no power going to it. Personnaly i use 1-2K res with led...i like it bright...but it depends on the led you use tough.

Picture are always helpfull when they are clear!

Salut!

Dan

[64fx]

OK, here's what I found.

I swapped the transistors around, so they are right now.

Got these voltages:
Q1
C=8.82
B=3.68
E=3.26

Q2
C=8.82
B=3.68
E=3.26

IC
1=4.39
2=4.43
3=4.38
4=.1
5=4.39
6=4.39
7=4.38
8=8.77

The recommended voltages from GGG for the transistors are:
C=9
B-3
E=2.5

All the values for the IC appear to be right except pin 4.  I'm wondering if it's my DMM though because it sits around -.2v when the probes aren't touching anything.

Still no LED.  Realized though that I had a 10k resistor on it, so I'm replacing it with a 3.3k.  I use the high brightness blue LED's.  Sunglasses will be required to use this pedal!

[64fx]

Getting sound but no LED...  Gonna replace the LED in case I burned it up somewhere along the way.

[64fx]

It works!

Thanks so much for your help!

[caspercody]

Was it the transistors that was the problem?

[64fx]

Yep!  That was it!  I think I had blown the LED, so that's why it wasn't working.  It's cutting in and out a little, but I can wiggle the wires and it works fine, so it's nothing major.  Since I haven't put it in an enclosure yet I'm going to go back and check all my wiring, but the pcb seems solid now.
Thanks for your help!