Using a Volt meter (debugging a Tonebender)

[powerplayj]

I need a little help debugging my first cook book project (Solasound Tonebender clone).  I have read the stickies and faq but, need a bit more guidance.


Links
http://www.bigtonemusic.com/fuzzclonediagrams.html
http://www.bigtonemusic.com/mk2battery.html
http://www.bigtonemusic.com/fuzzclonejacksNground.html

Symptoms: Effect does not work while engaged although I do hear an increase in noise when rotating the pots clockwise.  Sound does travel through the pedal when it is bypassed.  

Checks: I have checked the orientation of the transistors and the electrolytic caps and I have also looked at the connections on the switch.

Debugging: Specificly, when following the path of the circuit I assume my black probe should be touching the input sleeve ground.  Where should I be starting with the positive probe on the circuit board?  (in other words, should I follow the signal path of the battery (pos. to neg.) or the ("in" to "out") pathway?)  Honestly, a brief explanation or link describing the relationship between the guitar signal and the power supply would be awesome!

Last, how can I use a VM to check the connections on the switch as well?

This is definitely a defining moment which will decide if I have the patience to do a true DIY pedal project.  I'm willing to listen to anyone who can help.

Thanks

[Fret Wire]

Do you actually have one of his Tonebender kits? If so, which...the LED or non-LED model? The non-led model uses pnp transistors with a postive ground layout, and the Led/DC jack model uses pnp transistors with a neg. ground layout.

Also, there are four different fuzz's he has:

Germanium non-led fuzz with pnp transistors and pos. ground
silicon non-led with npn transistors and neg. ground
Ge led/dc jack with pnp transistors and neg. ground
Si led/dc jack with npn transistors and neg. ground

The kit site instructions cover both grounding schemes. The new sticky does mention including whether a ckt such as a fuzz is using pnp/npn transistors in a pos./neg. ground layout. This is important, as it effects both the on-board layout and off-board wiring.

[dualaud]

http://www.diyguitarist.com/PDF_Files/DIY-AudioTester.pdf
i highly recommend making an audio probe.
its great.

in fact, its so great, that i just had do put it together, and my original rat II worked again w/o me doing anything.
i nearly gave up on the rat.
the switch was broken, i replaced it; the device would work w/o box; put it back into its box -> stopped to work; :?:
threw it in the corner and after a week took it out of the corner again; assembled my audio probe; took the rat out of its box, and it just worked. then i found that the battery connection was broken. replaced it and everything is fine now!
so often its just a broken connection or maybe bad pot (but there should still be sound coming from it). pots are just that, pots.

beep through connections like switches and jacks with your DMM.
could be a cold solder joint.

cheers,
dual


ps. this is an inspiring  thread as well.

[powerplayj]

It's the non L.E.D. / non DC jack Ge fuzz.

[Fret Wire]

I need a little help debugging my first cook book project (Solasound Tonebender

It's the non L.E.D. / non DC jack Ge fuzz.

The non-led/dc jack Tonebender and Fuzz clones are both pnp pos. ground but, different ckts. One has two transistors, the other three.

http://www.bigtonemusic.com/Fuzzclone.html

http://www.bigtonemusic.com/TBclone.html

Which kit is it specifically? Then we can get to what to check component, wiring, and voltage wise.

Being a pos. ground ckt, you'll be placing your red probe on the jack sleeve (ground) and using the black probe on your components.

[powerplayj]

It is a positive grnd 3 tranny Ge version.  Thanks again for your patience.  

And regarding the mention of the audio probe....I plan to make one but, just need some guidance on how to follow the circuit and how to recognize a bad solder joint, etc. based on Voltage.

http://www.bigtonemusic.com/TBclone.html

Thanks for your patience Fret Wire........

[Fret Wire]

First measure your battery voltage. Then refer to the pic in step 2 of this link.
http://www.bigtonemusic.com/mk2battery.html

Put the battery in, switch on, cord in the input jack. Measure the voltages of the battery leads. The red battery lead ends on the sleeve of the input jack, and the black battery lead ends on the right side of the board marked "neg". You should get full battery voltage. Use the red DMM probe for ground and black to test the various voltages. Try the black probe on the red wire going from the input jack ring to the board also.

Take voltage readings from the + and - of the 47uf and 4.7 uf capacitor leads. And take voltages from each leg of all three trannys.
List the tranny voltages as:

Q1 e:
    b:
    c:
etc.

Take those voltages and get back with them.

[powerplayj]

I'm getting a bit of help too from Keith at BigToneMusic.com.............

with black probe on + battery and red probe on - battery, the reading = -9.26.

All my voltages are negative???

C1 = -8.92
C2 = -0.1
C3 = -8.76

Also, the 100k resistor adjacent to C2 gives a reading of -9.14 on the side opposite C2 and -0.1 on the connection adjacent to C2.

Keith said C3 should read 4.5-5.5

http://www.bulletinboards.com/cftree.cfm?comcode=jcm900&ViewType=E&UseNoFrame=yes&xx=x

[powerplayj]

ooops....just saw your message...let me try it

[powerplayj]

First measure your battery voltage. Then refer to the pic in step 2 of this link.
http://www.bigtonemusic.com/mk2battery.html

Put the battery in, switch on, cord in the input jack. Measure the voltages of the battery leads. The red battery lead ends on the sleeve of the input jack, and the black battery lead ends on the right side of the board marked "neg". You should get full battery voltage. 9.14Use the red DMM probe for ground and black to test the various voltages. Try the black probe on the red wire going from the input jack ring to the board also.  Actually, my red wire from the input jack ring goes to the battery and the red wire coming from the "pos" on the board goes to the input sleeve.  I made the change to correct this

Take voltage readings from the + and - of the 47uf and 4.7 uf capacitor leads. And take voltages from each leg of all three trannys.
List the tranny voltages as:

Q1 e: 0.0
    b: 0.0
    c: 8.88

Q2 e: 0.09
    b: 0.06
    c: 0.09

Q3 e: 0.05
    b: 0.09
    c: 8.74


etc.

Take those voltages and get back with them.

[powerplayj]

Actually, still got the problem........

[Fret Wire]

What were the voltages on both ends of the 4.7 and 47uf caps?

[powerplayj]

Both caps are 4.7uf and the cap at E1/E2 measures 0.0(-) and 0.05 (+).  The other cap measures 0.08 (-) and 0.05 (+).

[Fret Wire]

http://www.bigtonemusic.com/images/mk2wire9.jpg

Time to double check your electro orientation, transistor pinout, and touch up the solder joints. Check your voltages again.

[petemoore]

I've been always able to trust that the red lead from battery clip is +, I used to check that.
 So if you have red to + on the board, and read ground from the battery...probably you have the 'invert polarity' switch wrong [do they put these on DMM's?]. To change polarity, put the black lead [to ground].

[powerplayj]

http://www.bigtonemusic.com/images/mk2wire9.jpg

Time to double check your electro orientation, transistor pinout, and touch up the solder joints. Check your voltages again.

I touched up all the joints, checked all the component values and orientations assuming those electro caps are correct but, still no luck. Attached is a partial pic of the pot lugs which I am pretty sure are correct. Also, I jotted down a few voltages around the circuit. The latest values I get for the Q's are C1=5.91, C2=.08
C3=8.26. Also, the wires coming out of Q2 have a copper tint to them compared to the other transistors. Could this one be fried, faulty, etc?

http://www.bulletinboards.com/TreeMsg.cfm?msgid=776224&comcode=jcm900&caller=cftree&x=x&MgrCalling=No&CatName=Fuzz%20%20Lounge&UseNoFrame=yes#locc1