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output dc blocking

Started by alecacca, July 13, 2007, 07:58:47 AM

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alecacca

July 13, 2007, 07:58:47 AM
hey guys!
i've built the ggg tubescreamer but i have some popping problems (because there are 2v dc on the output i think). i've tried to put a led on the ouput and the led switch on and stay illuminated.
i've tried to bypass the output buffer and add the led on output and now when i switch on the pedal the led flash and then become dark... there is a tip for blocking this DC current that causes this annoyng pops??
thank you!   sorry for the bad english!  :icon_mrgreen:

Sir H C

#1
July 13, 2007, 12:09:57 PM
Do you have the capacitor on the output?  If so, then try a 1 meg resistor to ground, that will bleed off any DC.  Also that capacitor could be leaky and so you see the voltage there.

R.G.

#2
July 13, 2007, 12:24:49 PM
The GGG tubescreamer does not have DC on the output when built properly. I know - I did that layout.

It is likely that you have a problem with the construction of the circuit board. That board has an output capacitor to block DC from the output. If that is put in backwards, it will leak badly. You should not see DC on the output.

As to putting an LED on the output - why are you doing that?

No apologies are needed for bad English, except for those of us who should be able to use it better!  :icon_biggrin:
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

alecacca

#3
July 13, 2007, 07:36:05 PM
Quote from: R.G. on July 13, 2007, 12:24:49 PM
The GGG tubescreamer does not have DC on the output when built properly. I know - I did that layout.
wooooww!

Quote from: R.G. on July 13, 2007, 12:24:49 PM
It is likely that you have a problem with the construction of the circuit board. That board has an output capacitor to block DC from the output. If that is put in backwards, it will leak badly. You should not see DC on the output.
i checked the board so many times.. but it's all right and there aren't short circuits..i seen the output cap (C11- 10uf?) and it's connected in the right way..

Quote from: R.G. on July 13, 2007, 12:24:49 PM
As to putting an LED on the output - why are you doing that?
to see if there is the dc voltage.. my dmm sometimes don't work good.

Quote from: Sir H C on July 13, 2007, 12:09:57 PM
Do you have the capacitor on the output?  If so, then try a 1 meg resistor to ground, that will bleed off any DC.  Also that capacitor could be leaky and so you see the voltage there.
i tried that trick but don't work.. i also go down with 30k and 20k but the effect pop anyways..   :icon_frown:

when i have time i post a pic of the pcb
thanks!
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