Fuzz Face help needed

[hellwood]

the schematic shows a 500k volume pot.

look for the obvious things like miswired pots, miswired switch, a bad transistor, bridged solder traces, misread schematic, polarized caps backwards and im not joking about the ground thing. you are going to kick yourself in the ass if thats the problem!
 

[Fenderstrat]

hehe, ive given up on that circuit, it was my first build and i can't seem to fix it. i've taken the parts off and started from scratch, its much neater so far (no thousands of wires going all over the place etc )    thanks heaps for all your help, i've learnt alot. I'll keep working on it and hopefully post some pics if it works.
Just one more newbie question before i leave you alone, Does a 500k linear pot do the same thing as a 500k volume pot?

Thanks again - Rhys

[GREEN FUZ]

Just one more newbie question before i leave you alone, Does a 500k linear pot do the same thing as a 500k volume pot?

Linear just describes the taper. Quoting from R G Keen now."What is taper? It's just the ratio of the resistance already passed as the pot turns to the total resistance of the pot, described as a curve."

So effectively, within reason, any pot can be used to control any parameter, volume/tone/resonance etc. Different tapers are often used for specific applications though, horses for courses. For more in depth explanation, go here.

http://www.geofex.com/Article_Folders/potsecrets/potscret.htm

[oskar]

hmmm.. it seems im using a 500k linear pot for volume control.     could this be my problem.... 

No... sorry, that's not it   
The log pots are used for audio level controls. Linears will work but when you turn it from zero the volume will
first increase very fast and on the upper half you wouldn't experience that much of action.

[R.G.]

Ok, thanks heaps for that. and you just happen to be perfectly correct!  icon_eek , because last night after being completley stumped as to what the problem was, i tested every single component (caps, resistors pots etc.) and i found that the resistance of the resistors was only about half what it should be. the 33k was only 13k, and the 18k had dropped to 12. the 1k and 100k were still perfect though.  Huh  after noticing that i changed them over, and measured the resistors before i put them in. 33k and 18k, as they should be. I soldered them in and measured them, still the right values. after this my fuzz face worked perfectly, for a while.  I woke up this morning eager to use it a bit more! and bang, same problem again. the resistance had dropped back to 12k and 15k.

It is very difficult to measure resistors accurately when they are soldered into a circuit. They almost always measure lower than the actual value. When you pull them back out of circuit, they read normally. This is because when you measure in the circuit, everything that is connected to the ends of the resistor is electrically in parallel with the resistor and this gives a false reading.

I'm positive its not a misread, because not only do the measurements drop, the sound is sacrificed horribly, and when i measure the rest of the resistors they measure fine. the resistors are losing their resistance.

They're really not. I think it's more likely that you have an electrolytic cap in backwards and over a some time, it breaks down and looks shorted.

Q1  C: 5.92v
      B: 0.07v
      E: 0.00

Q2 C: 9.28v
     B:  5.89v
     E: 5.92v

This indicates that the emitter circuit of Q2 is open. There's probably a bad connection from emitter of Q2 to ground through your fuzz pot.

[Fenderstrat]

ok, i know you all must be getting pretty sick of me by now. I started from scratch and built the circuit again, i used an audio taper pot for the volume, i ran a ground wire around all the inputs/outputs/ pot chassis etc. I finished and  plugged it into the amp. (i'm sure you know the feeling )
and beauty, it dosent work.

I've taken more voltage readings.

battery: 9.22 volts

Q1
C: 0.16 volts
B: 0.08 volts
E: 0.00 volts

Q2
C: 9.14 volts
B: 0.16 volts
E: 0.22 volts


any photo requests are welcome, but at the moment i don't really know what to take a photo of.

Cheers- Rhys

[oskar]

1. You should really check that the thing works before you build it into a box. Build it in stages. Ok, so
maybe it is only ten little components... Some weeks ago I managed to get three errors in a bufferstage
containing only 6 parts!             

2. Photos needed of pcb, both sides. Closeups on the solderside...

The worst thing that could happen if you don't get it to work this time would be quitting with electronics,
not jumping out of the nearest window...                                 

ps. For the changing resistances. The DVM puts out a tiny current across the resistor it's meassuring. If you have a capacitor connected
it will be charged or discharged by the DVM and you will get a failing reading and a reading that changes over time.

[momiel]

What did u use? PCB? Breadbord, Veroboard? Post some pictures of the whole board...

[GREEN FUZ]

Another couple of points:

1. What sort of transistors are you using? PNP? NPN? Get a datasheet and check the pinout.

2. How is your soldering? It`s easy to create a myriad of short-circuits if your technique is sloppy. I should know.

[Fenderstrat]

hahahah, thanks oskar. My house is only 1 storey, so no life threatening injuries there. unless i land in the garden in a rose bush or something..
   Yeh, its quite embarrasing

back to business

  I'm using PNP AC128's, Im pretty certain the pin out is right.  Emitter is the one with the notch, base is the middle one and collector is the other one.
 
  I don't think my soldering is too bad, though you may think otherwise.





tempting..

   
sorry for confusing wires, i only had red, blue and tiny pieces of white.

I tried to colour in the red wires that are sposed to be black, didnt work very well.

[oskar]

Allrightie then... It's kind of Chagall or Picasso, but that is what you end up with the perf-things.
The lugs marked with a green circle are disconnected when you connect something to it ( the metal "things" in the pink circle are raised )
Do all connections on the other side...
This function is for "normalised connections" like the headphone jack on your amp. If you connect a headphone the speaker gets
disconnected...
Though it looks like you're aware of this I don't think anything should be connected on that side on any of the jacks.


The volume pot looks anything but familiar... stereo?

I would try this... one at a time!
1. The blue wire going from jack to jack... boldly remove... what is that anyway?!
2. Disconnect the volume pot (that's the left one right?) from the board and take the signal directly from the cap.
3. Hardwire the batteryclip/connector to the Perf-thing without the in-jack.

It's kind-of hard to follow and your construction actually look all but too similar to what my use to look like, really...

I personally build things one step at a time and don't connect jacks and outboard stuff untill I know the board is OK.
( which is a good thing because my stuff never works anyway... )

EDIT... I went through the thread once more just to make sure I hadn't missed out on something... which I had...
i.e. the fact that it actually worked once... I really don't get it!!!

[GREEN FUZ]

I don't think my soldering is too bad, though you may think otherwise.

Ok, as you say, not too bad. You should see some of mine  . Even so, to my mind, they have the look of dry solder joints. These often lead to failed or intermittent connections even if everything looks right. The raised, blobby aspect is indicative of this. You should be aiming for a neat little peak of solder. Be sparing with it. I know how it is when you feel the Soldering Iron is a tool of the Devil conspiring against you. When the solder doesn`t appear to want to stick you keep piling more on. There are a couple of guides in the DIY FAQ that will help. Iron maintenance is also essential. Keep it clean and tinned. Again, check out the guides.
Even if this isn`t the cause of your Fuzz Face problem, there is every chance that somewhere down the line a joint will fail.

[Fenderstrat]

hmmm.. quite an horrible excuse for a circuit isnt it..    I'm sure you have an idea of how frustrated i am

heh, i know what you mean about the soldering iron thing Green fuz.   That little high tensile power cord that seem to always want to flick the soldering iron back into your face.

The volume pot is just a push pull thing i had left over from when i built my guitar.

One note on this circuit is that it has never worked. I built a circuit that had maybe twice as many wires as this. this is the one that worked then went down with the same problem as this one.  The pictures here are of another circuit that i finished building the other day because i couldn't fix the other one.
So i've already done all the soldering again to the best of my ability... (i heat up the surface with the iron and then just touch the stick to the edge of the iron as it melts onto the wire, is that right?)
The thing is, you know how the emitter of Q1 goes to ground?  well if i ground it through the capacitor, i have normal volume, but no noticeable fuzz.   If i put it straight to the ground wire i have very little volume and a very small amount of fuzz, but hardly noticeable. Which way should i connect it?

*rips out hair*

maybe i'd be better of eating these circuits and just buying a fuzz pedal.

[GREEN FUZ]

heat up the surface with the iron and then just touch the stick to the edge of the iron as it melts onto the wire, is that right?)

This is a classic mistake, easily made. Done correctly, the solder should flow easily onto the previously heated components without having to touch the iron at all. There are so many variables to good soldering. The temperature has to be just right. Not too hot. The components and board need to be clean as does the Iron. It`s one of those things that need practice before you can get a feel for it.

Back to your circuit. You mentioned that a previous attempt you made worked initially before failing. This could mean a blown component or it could be an example of poor soldering. I would be tempted to go back and `reflow` the solder joints. Sometimes you can magically resurrect a faulty circuit in this way. There`s nothing like a working pedal to keep that initial enthusiasm going. The opposite also holds true, I know how frustrating it can be. Keep a clear head, try to work methodically, don`t rush things. If it all gets too much put it aside and do something else before approaching again with a fresh mind.


If it still doesn`t work, trash it and everything else in sight with a Baseball bat while cursing God,your Mother,the World or anyone else who might be responsible for it`s failure. Usually works for me .

[oskar]

hmmm.. quite an horrible excuse for a circuit isnt it..    I'm sure you have an idea of how frustrated i am

(i heat up the surface with the iron and then just touch the stick to the edge of the iron as it melts onto the wire, is that right?)
1. Let the iron become hot.
2. Melt some of the "tin?" (in swedish lödtenn(sorry completely blank)) on the tip of the iron, you NEED to do this, it improves the contact and transfer
the heat so that when you...
3. Put the soldering iron to the, whatever you are soldering, and wait 2-3 sec.
4. Now! you finally add tin to finally complete the solder joint.
It is specially important for heatsensitive components like... hm... germanium transistors... ( I think they are quite sensitive actually!!)
that the process is rather fast...

maybe i'd be better of eating these circuits and just buying a fuzz pedal.

not an option... It's not only your problem now you know!!!

[Fenderstrat]

hahahahah!   thanks guys. so you seem to think its a soldering problem?   ok, i'll remelt all my joints again, and change the connection on those jacks (i was never too sure about them, found them lying around and they looked like the ones in my wah pedal so i thought, oh yeah beauty.)
The wah pedal was what actually got me interested in the whole effects building thing. I didn't like it and wondered if there were any mods i could do. and were there!


anyway

I made a layout diagram of how its made, its still very confusing but probably better than a perf board with wires and black texta all over the place.


See any problems with that?

The green wires are the inputs/outputs of the circuit to the pots.
just thought i'd complicate things a little more 



And heres the Schem.



Thanks again

-Rhys

[newbie builder]

You've got the polarity of the input 2.2uf capacitor reversed on your layout- the + should go to the input, - to the next component. On circuit diagrams the | side is the + and the ( side is the - of a capacitor. I can't tell because there are too many red wires where the other electrolytic is connected, (i.e. which side is going to ground, which is going to the tone pot), but that might be reversed too if you reversed the first one.

[oskar]

See any problems with that?

YES...
fedback shorted to ground...
cut the green and pink crossed connector... that is if it marks a connection.
could this be IT?
Next time you could mount the 22uF cap on the pot directly...

[oskar]

You've got the polarity of the input 2.2uf capacitor reversed on your layout- the + should go to the input, - to the next component. On circuit diagrams the | side is the + and the ( side is the - of a capacitor. I can't tell because there are too many red wires where the other electrolytic is connected, (i.e. which side is going to ground, which is going to the tone pot), but that might be reversed too if you reversed the first one.

Hi Evan...   
This pedal is running with POSITIVE ground, awful isn't it?  ( Probably because Roger Mayer is Brittish and you know, they just do
everything the opposite way... )
Anyway the voltage on Q1 base is actually negative... cap is OK!

[Fenderstrat]

nope, sorry oskar, thats just my not so hot skills with layout creator

I'm getting an electrics friend to have a look at it today, maybe something will come out of that.