Tweak-O help

[lethargist]

Hi,

I know that this may be a really hard qn to answer, but i am having trouble building the tweak-o effect. it is my first effect, and i have built it on a breadboard just to test it out first, but it doesn't seem to be working very well... The bypass effect is working fine, but when i turn the effect on, a strange thing happens.. It just seems to "turn down" the volume of my guitar, but does not add any fuzz to the sound.. adjusting the two pots also seems to nothing but increase or decrease the volume.. still no fuzz.. I measured the voltages at each of the three pins of the transistor, and they are all correct according to the step by step guide on small bear.. any ideas?

Thanks guys

[puretube]

hi there:
maybe someone can help, if we put a link to the schematic here:
http://www.smallbearelec.com/Projects/TweakO/TweakO.htm

:wink:

(sorry - too busy myself...  :cry: )

[petemoore]

Breadboard for the first project, I don't remember reading that one before, congratulations...good thinking!!!
 THe DMM, it's manual, and the audio injector are my best debugging friends.
 Sometimes just staring at the <- schematic ->and board is enough.
 heres a couple little things I like to do  
 Test for continuity [shorts] between + and - [9V and Ground] on the board or circuits battery clip.
 check the voltage from ground of the Emitter base and Collector of the transistor.
 Plug the thing into amp and supply power 9v to the circuit, touch the wiper of the volume pot [middle lug]. You Should hear a buzz, if not there's a problem between the volpot and the amp.
 Then touch the outer lugs of the pot. [a conductive rod makes it easier to 'connect your body to the circuit points for testing']. When touching the lug connected to ground you should hear Nothing. With the output volume turnied all the way up, you should hear a buzz alot like when you touch the wiper. If the above circumstances exist, your volume pot is probably working properly.
 Follow the signal path, and touch at points on it as you work your way toward the middle then input of the circuit. You should hear a more faint sound when 'agitating' [touching to] the collector than the base if the transistor is amplifying.
 If at a point in the signal path the sound is quite attenuated or no sound, look for a problem near that area.
 It is a good idea to check resistor color codes and verify the 'actual' value of resistors using the DMM. Depending on your resistor types a ~10% tolerance [off from the stated value] is normal.
 An audio injector [instead of your thumb] can be used to 'inject signal to points within the circuit for testing. Taping a note down on a toy keyboard is a way to get a constant signal source, I use the 'thumbuzz method' cause it's too easy.
 Just take the transistor pin voltages [E,B and C ..from ground] and post the readings here.
 Reads at GEO give instruction as how to bias transistors, as well as very much else.

[lethargist]

thanks for putting up the link puretube and thank you petemoore for your help. I will have another go at it tomorrow (its 1:20 am here - time for some sleep) and hopefully post some of my findings...

I just thought of one more thing that the effect is doind that may shed a little more light on where the problem is... recall i said that with the effect turned on it just seems to turn down the volume.. well if i disconnect the battery while i am playing the volume will come back up, and then once again die away.. this happens over a period of 10 to 20 seconds... strange...

anyheys.. time to get some sleep

Jarrod

[petemoore]

Good thing to do, I forgot to mention slleep and eat [coffee doesn't hurt if you like it], when it's getting limited returns for your time, and fatigue sets in, there is no substitute for sleep [never wiil be a substitute for sleep]...
 Getting stuck late and tired is not conducive to maintaining optimal debugging performance.

[Jason Stout]

Do you have the 2.2µF cap oriented correctly?

+ Side to emitter
- Side to ground

Also: First connect the circuit without switching, this simplifies things.

Here's Joes schematic: http://web.archive.org/web/20010628010107/home.i1.net/~joe1/images/tweako.gif

[lethargist]

The schematic asks for only one polarised cap (2200uF) but i have used electrolytic caps for all but one.. could this be the problem? i have checked several times and they are all orientated correctly..

[Jason Stout]

The schematic asks for only one polarised cap (2200uF) but i have used electrolytic caps for all but one.. could this be the problem? i have checked several times and they are all orientated correctly..

Are you using the correct values? 0.1µF, 0.01µF, and 0.001µF are not common values for electrolytic caps. Are they tantalum?

Cap type dosen't really matter, values matter much more. just make sure that if the cap is polarised it is oriented correctly.

Is the transistor in the circuit correctly? How do you know which leg is which? What transistor are you using?

Also check out this page for some good tips!

[petemoore]

Using non-polarized caps for everything except the larger values, in this case the 2.2uf, simplifies cap polarity issues...make sure the 2.2uf has it's - marking going to ground.

[lethargist]

Are you using the correct values? 0.1µF, 0.01µF, and 0.001µF are not common values for electrolytic caps. Are they tantalum?

the cap values are 0.1mfd, 0.01mfd and 0.001mfd.. whcih make them 100µF, 10µF, and 1µF? thats right isn't it? i could ONLY find those as electrolytic

[petemoore]

The tweak-O uses
 .1uf    [x2]
 .01uf   [x2]
 .001uf
 2.2uf Caps
 The 2.2 would probably be an electrolytic polarized cap.
 There must be a wiring error, using larger caps would let more bass through

[Lonestarjohnny]

.1uf =100 nanofarad
.01uf=10 nanofarad
.001uf=1 nanofarad
uf=microfarad
microfarad = larger in size- nanofarad = smaller in size- picofarad = smallest in size
Johnny

[Jason Stout]

the cap values are 0.1mfd, 0.01mfd and 0.001mfd.. whcih make them 100µF, 10µF, and 1µF? thats right isn't it? i could ONLY find those as electrolytic

Your post is confusing me! O.K. when you type mfd do you meen milli Farad? if so 0.1 millifarad does = 100 µFarad (µ = micro) We don't commonly use milli Farads, we use micro, nano, and pico.

the cap values ARE in microfarads (µF) NOT milli. I suspect that all your capacitors are an order of 10^3 too large.

The largest capacitor is the emitter bypass capacitor, 2.2 microfarads.

[puretube]

folks who don`t have the "µ" sign on their keyboard,
often type "0.1mF" or "0.1uF", when they mean: "100nF" or "0.1µF...

[lethargist]

ok.. maybe that is the problem... i just looked at the schematic and saw all the caps were marked in mfd, and assumed that this meant milli-farads.. i will replace them all with micro-farad caps and see what happens

[Mark Hammer]

Millifarad caps?  That is going to be a BIG Tweak-O!!

I'm reminded of "This is Spinal Tap", where the band's guitarist, Nigel Tufnel, quickly sketches out his idea for a stage prop on a napkin and hands it to their manager, who gives it to an artist to make a model of Stonehenge.  The artist returns with the prop, but the napkin unfortunately used the symbol for "inches" (") when it should have said "feet" (').  When the 18" high model of Stonehenge is first lowered to the stage during a performance, the band is startled to see this little foot-stool of a thing, which is smaller than the dwarves they have hired to dance *under* the prop during the stage number.

Yes, abbreviations for measurements can mean a LOT!!!  :lol:  :lol: