DEBUG: Tonepad Stock Big Muff

[Christoph.H]

Decided to try to build a big muff with stock specs from tonepad.com

Schematic: http://www.tonepad.com/getFile.asp?id=95 (stock)

Layout: http://img534.imageshack.us/img534/3895/kopplingsschemadelar.jpg

Since I am pretty new to electronics, I can't manage to see what's wrong myself, hope you guys can help...

When I just connect the battery, and stick the negative lead to ground, I get 0V readings everywhere. And when I measure between positive battery clip and ground I get 0V, but between negative battery clip and ground I get -9.36V.
When I however connect amp and instrument cables I get the following readings:

Battery (between positive clip and ground): 9.36V

Q1
B: 0.633 V
E: 35.3 mV
C: 3.98 V

Q2
B: 0.633 V
E: 34.6 mV
C: 4.03 V

Q3
B: 0.630 V
E: 33.9 mV
C: 3.96 V

Q4
B: 1.758 V
E: 1.16 V
C: 3.99 V

D1
A: 0.512 V
K: 0.633 V

D2
A: 0.633 V
K: 0.512 V

D3
A: 0.502 V
K: 0.631 V

D4
A: 0.631 V
K: 0.502 V

The pedal is totally dead, not a sound, when turned on. When I bypass the circuit the signal goes through fine though, and I've checked all the wiring a dozen times, it's in its order.
I didn't substitute any parts, all is as it's suggested in the tonepad schematic. I did however, when I first tested it, reverse the amp/instrument cables. I plugged the guitar to the output and amp to input.
I built the board by using photoresist copper clad, and it came out pretty much flawlessly.

[Govmnt_Lacky]

Pictures of your build would help greatly.

Double check your off board wiring (Input/Output Jacks, 3PDT, Wiring to pots, wiring to board)

At first glance, the only things that look "off" are your Emitter volatges on Q1, Q2, and Q3 however, I am NOT an expert on Big Muff circuits.

My bet is that you have an error in your off board wiring. 

Good Luck 

[Christoph.H]

Yeah I'll take pictures when I've got the time :p

Re-checked offboard wiring, still looks fine! Yeah I'm guessing it's those three trannies, could it have something to do with that I accidently reversed input/output?

[blooze_man]

could it have something to do with that I accidently reversed input/output?

Most likely yes.

[Govmnt_Lacky]

...could it have something to do with that I accidently reversed input/output?

Highly unlikely if you mean that you accidentally inserted your guitar cable into the amp jack and vice/versa but, not out of the realm of possibility if you actually WIRED the input and output backwards to/on the board.

Also, QUADRUPLE CHECK ALL of your component values and placement. Make sure you didn't accidently insert a 1M resistor into a 100 ohm spot, a .01uF cap instead of a .1uF cap, etc.

Good Luck  

[Govmnt_Lacky]

Those voltages look consistant with what JD (GGG) lists from his build of the Big Muff:

http://www.generalguitargadgets.com/pdf/ggg_bmp_instruct.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

[Christoph.H]

Those voltages look consistant with what JD (GGG) lists from his build of the Big Muff:

http://www.generalguitargadgets.com/pdf/ggg_bmp_instruct.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Indeed, thank you very much!

I'll get to checking the components, although I've already done that once...

...could it have something to do with that I accidently reversed input/output?

Highly unlikely if you mean that you accidentally inserted your guitar cable into the amp jack and vice/versa but, not out of the realm of possibility if you actually WIRED the input and output backwards to/on the board.

I meant that I inserted my guitar cable into the amp jack and vice/versa

[Christoph.H]

Here are some pics of the build... oversized PCB because I wasn't too confident with my soldering...  
Turned out good though..  








What I've done so far:

-Checked transistor voltages, which seem to be in order
-Checked that all connections that should go to ground, do so with no resistance
-Checked offboard wiring approximately a thousand times
-Checked all components
-Checked for bad solder joints

[Govmnt_Lacky]

Just from looking at your pictures I have two recommendations:

1) Check and RECHECK your PCB for solder bridges. It looks like there may be some on the board (from the pics)

2) You definitely need to re-solder your pots. Do not solder the wires to the little holes by the lugs as it may run INTO the pot and cause problems. I recommend that you desolder ALL pots, check their resistances to ensure they are still good, then.... solder the wires to the LUGS. In the case of the PCB board mount pot (the one with the pins), you should curl the wire around the pin and solder them.


Good Luck 

[Christoph.H]

Just from looking at your pictures I have two recommendations:

1) Check and RECHECK your PCB for solder bridges. It looks like there may be some on the board (from the pics)

2) You definitely need to re-solder your pots. Do not solder the wires to the little holes by the lugs as it may run INTO the pot and cause problems. I recommend that you desolder ALL pots, check their resistances to ensure they are still good, then.... solder the wires to the LUGS. In the case of the PCB board mount pot (the one with the pins), you should curl the wire around the pin and solder them.


Good Luck  

Thank you, will do that!
I noticed something else, my pots have the little "marker" on the right hand side when looking at them from behind with the lugs facing downwards,
whereas in every other big muff pic
the "marker" is on the left hand side as it is in this picture:



What is the difference and might I have soldered the pots the wrong way since I just followed a layout-picture that showed the pots with the "marker" to the left,
so I just flipped the pot upside down and soldered it that way?

[jefe]

It looks like you soldered to the pots right up near the body, instead of on the solder pins. Are you sure you didn't overheat the pots? I mean, I kinda doubt it, but since you're new to soldering, it makes me wonder.

Also, it looks like you didn't solder anything to the ground lug of the output jack. That's fine, as long as your'e absolutely sure it's grounded through the chassis. Make sure you've got continuity between that lug and the box.

[Govmnt_Lacky]

I noticed something else, my pots have the little "marker" on the right hand side when looking at them from behind with the lugs facing downwards,
whereas in every other big muff pic

That is of no consequence. The marker should make no difference. It is just a manufacturing difference.

[Christoph.H]

Well, I'll check the wiring, components and values ONE last time and if it's still dead I'm just gonna build a new PCB... 

Thans ALOT for all the help though, you guys really helped me learn and improve for my next build!