Author Topic: I'm having some trouble  (Read 6843 times)

SmurfJ

I'm having some trouble
« on: August 02, 2007, 10:11:26 PM »
Okay... im very new (so new i didnt want to start with the beginner project and soldering.) to all of this

I bought myself a breadboard and set it up like in the tutorial...
I understand the whole power sectino and all of that.  My .01uF capacitor (C1) is ceramic disc instead of the metal film (?) thats in yours.
And i couldnt get any 47pf capacitors, so i put 4 100pf caps in a series off to the side of the board and used jumpers to get it back over.
everything is in place, and without diodes (or with) i get nothing but buzz... no sound AT ALL...
i also have for resistors r3, r9, and r8 1/2 Watt instead of 1/4... but those are power.. and i checked with the multimeter and they are fine...
i was going to put this into a perboard after i finished and had it working.. but i dont want to solder everything to find out it isnt.
for the gain knob, why is it that it is grounded twice? could this be a flaw?


gaussmarkov

Re: I'm having some trouble
« Reply #1 on: August 02, 2007, 11:51:48 PM »
we will have to debug your breadboard build just like we debug any perfboard or pcb build. :icon_wink:  but we have the benefit of being able to fix your mistakes very easily.  :icon_cool:

first, to answer your question about the gain knob.  the pot, which can be used generally as a voltage divider (like the fixed voltage divider in the power section) can be specialized to work as a variable resistor.  this is done by connecting the wiper (middle lug) to one of the other lugs.  by shorting those two lugs all of the resistance between the connected pair and the other lug is the resistance between the wiper and the unconnected lug.

so, no, it's not a a flaw.  it is just that the gain knob is a variable resistor between the feedback loop and ground.

if you would like to read a sequence of notes about resistors, starting with fixed resistors and working all the way through to mods on pots, you might try the ones i put up on gaussmarkov.net:  resistors.  there are links to R.G.'s stuff there and some other sites as well.

your ceramic disc capacitor will be fine.  and your series of 100pF caps also.  if you want to match the 47pF capacitance, i think you only need to put two of them in series.  that should give you 50pF.

so ... on to debugging.  the debugging page linked at the top of the pages of this forum is required reading.  so are the links in that page.  among the things that are described there is the audio probe and voltage readings on ICs and transistors.

you need to build an audio probe (it's easy) so that we can trace the signal through your circuit by listening to it at different points and seeing where the signal stops.  with the breadboard set up, you can actually just build the audio probe onto the board -- it's just a capacitor and two jumpers.  one jumper will go to a net on the breadboard from one side of the capacitor and the other will go to your output jack from the other side of the capacitor.

you also need to read and report the voltages on each pin of the IC.  the ones that i got for a working circuit are in Topic: 3. Hooking Up the IC and these are the approximate values that you should be reading.

one last thought:  you may not have grounded everything properly.  use the continuity check on your DMM to make sure that everything that is supposed to be grounded is connected to the ground post of your breadboard, including the ground lugs of the input and output jacks.

i am looking forward to helping you get your breadboard build working.   :icon_biggrin:
gaussmarkov.net:  layouts & eagle

SmurfJ

Re: I'm having some trouble
« Reply #2 on: August 05, 2007, 10:34:18 AM »
 :) :D :icon_biggrin: It works!
Foudn the rpoblem, and feel very deceived.  One of the slots in my breadboard (C22) is broken.  It wont hold wire or anything, and just doesnt work.  That kinda interfered a bit, so i used some jumpers to move the capacitos away from there, then umped it back. works now.  I was wondering do different diodes make for a more distorted sound? If i add in a stomp switch, will i need the 2.2m resistor? what is that resistors actual purpose??

gaussmarkov

Re: I'm having some trouble
« Reply #3 on: August 05, 2007, 12:47:13 PM »
:) :D :icon_biggrin: It works!

sweet! congratulations! :icon_biggrin:

Foudn the rpoblem, and feel very deceived.  One of the slots in my breadboard (C22) is broken.  It wont hold wire or anything, and just doesnt work.  That kinda interfered a bit, so i used some jumpers to move the capacitos away from there, then umped it back. works now. 

nice work!  :icon_cool: i have never had a bad breadboard slot, but i'm sure it happens.  your work around is another example of the flexibility of breadboards in the first place. :icon_wink:

I was wondering do different diodes make for a more distorted sound? If i add in a stomp switch, will i need the 2.2m resistor? what is that resistors actual purpose??

different diodes do have different sounds.  so experiment and see what sounds good to you.  and search the forum ... i am sure that you will find many comments about diode choices.

the 2.2M resistor is called a "pull-down" resistor.  it is there to help prevent a pop when the circuit is switched on.  again, by searching you will find explanations of this in the forum.  so, yes, when you add a switch you will probably want to add that resistor.  it isn't necessary but it is helpful.  you can also read about it on R.G.'s site at  The Ins and Outs of Bypassing Effects or on gaussmarkov.net at capacitors: dc and ac.
gaussmarkov.net:  layouts & eagle

SmurfJ

Re: I'm having some trouble
« Reply #4 on: August 05, 2007, 01:16:02 PM »
How could i add a 3pdt switch in. i found a simple instruction with a stereo jack. but hwo do i coordinate a bypass with 2 mono jacks (and an led)

CGDARK

Re: I'm having some trouble
« Reply #5 on: August 05, 2007, 01:21:30 PM »
How could i add a 3pdt switch in. i found a simple instruction with a stereo jack. but hwo do i coordinate a bypass with 2 mono jacks (and an led)


Check the Many Bypass Switching Options section at:
http://generalguitargadgets.com/index.php?option=com_content&task=view&id=33&Itemid=27

CG