NOOB Question Regarding Debugging First Stompbox

[texstrat]

I purchased a Late 60's Fuzz Face kit from GGG and I have put it together based on the layout. I plug in the amp/guitar and it plays fine in bypass. I switch to effect and I get nothing. I made a audio probe using a 0.1uf 250V capacitor to test the circuit and all that I am getting is sound from my input, yellow wire from input jack to switch, and the bias pot, green wire going to switch. I have checked and re-checked my solder joints for cold solder joints, loose wires, etc. I have been looking and working on this for so long that I am afraid I am over looking something. Also I have noticed that the 9V battery is getting hot as I am tested with the probe, it was not doing that before. I am truly at a loss as to what to do.

Particulars to the kit:
PNP positive ground
I am using the optional diode in D3 and 1M resistor in R1
transistors are the 2N3906

Here are some pictures of my build so far:







Since GGG doesn't want the stuff posted on other sites, here are the links to the layout, schematic and build instructions
Layout - http://www.generalguitargadgets.com/pdf/ggg_ff5_lo_b69.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a
Schematic - http://www.generalguitargadgets.com/pdf/ggg_ff5_sc_b69.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a
Build - http://www.generalguitargadgets.com/pdf/ggg_ff5_instruct.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

[texstrat]

Ok, I found why the battery was getting hot, one leg of the transistor in Q2 was not secure. I think my problem lies with the orientation of the 2n3906 transistors. I am new to reading the schematics, but could someone look at the schematic and tell me which way to orient the transistors.

Thanks.

[Jhouse]

Could you post voltages for your transistors? It's hard to see things only from pictures.

THIS is the datasheet for the transistors.

Also, I think your Q1 may need to be reversed. Keep the socket in and just turn that bad boy around.

[texstrat]

Here is another picture of the transistors. I had a couple of 2N3906 on hand, so I used those.



Here are the values:

Q1
Positive lead to base
BE 1.5mv
BC 0.0mv
CE 6.1mv (positive lead to emitter)

Negative lead to base
BE 2.1mv
BC 0.0mv
CE 0.1mv (negative lead to emitter)

Q2
Positive lead to base
BE 0.4mv
BC 0.0mv
CE 3.2mv (positive lead to emitter)

Negative lead to base
BE 0.8mv
BC 0.0mv
CE 3.3mv (negative lead to emitter)

[Jhouse]

Place the transistors so that both of the flat sides are facing each other. You turned around Q2.

Also, put your black (negative) probe on your ground and use the red (positive) probe for each leg. In your build hyperlink that you gave if you scroll down to the very bottom of the page, it gives what your Q values should be.

[petemoore]

  Battery gets hot indicates very likely shorted [or near shorting condition] at the PS, measure for No Connection at the powersupply input [under any conditions including all it will see, input jack, DC jack, battery etc. make it more than just 1 circuit as the DC jack switches, as well the stereo jack and mono plug form a switch when the plug is put in the jack: the sleeve of the mono plug spans across the ring/sleeve of the jack, connecting them.
  If shorting condition is detected between +/- [set the DMM to beep when the probes touch and put them across the power rails] eliminate it before applying power.

[texstrat]

Place the transistors so that both of the flat sides are facing each other. You turned around Q2.

Also, put your black (negative) probe on your ground and use the red (positive) probe for each leg. In your build hyperlink that you gave if you scroll down to the very bottom of the page, it gives what your Q values should be.

With or without the battery connected?

Also I found that I had put a 1K resistor were a 100K resistor was needed between Q1 and Q2. Now the transistors, flat sides, are facing each other.

[texstrat]

  Battery gets hot indicates very likely shorted [or near shorting condition] at the PS, measure for No Connection at the powersupply input [under any conditions including all it will see, input jack, DC jack, battery etc. make it more than just 1 circuit as the DC jack switches, as well the stereo jack and mono plug form a switch when the plug is put in the jack: the sleeve of the mono plug spans across the ring/sleeve of the jack, connecting them.
  If shorting condition is detected between +/- [set the DMM to beep when the probes touch and put them across the power rails] eliminate it before applying power.

Pete, I found that one leg of the transistor was not seated in the socket and that was causing the short.

[Jhouse]

With the battery in and a cable in the input jack.

[texstrat]

Ok, fresh 9V, 9.50V, and the following values for each leg. The FF was in bypass.

Q1
C - 8.00 mV
B - 8.83 mV
E - 9.45 mV

Q2
C - 4.15 mV
B - 8.00 mV
E - 8.66 mV

[texstrat]

I have another pair of 2N3906 that I checked and here are those values:

Q1
C - 8.03
B - 8.84
E - 9.46

Q2
C - 4.09
B - 8.02
E - 8.67

[texstrat]

Could you post voltages for your transistors? It's hard to see things only from pictures.

THIS is the datasheet for the transistors.

Also, I think your Q1 may need to be reversed. Keep the socket in and just turn that bad boy around.

Is this the correct orientation?

[petemoore]

Q1
C - 8.00 mV  Grounding the emitter may bring this voltage nearer to 1/2 of supply.
B - 8.83 mV
E - 9.45 mV  This lead should connect to ground = 0.0v.

Q2
C - 4.15 mV
B - 8.00 mV
E - 8.66 mV
  Q2 bias may be getting thrown off by Q1E's no ground situation.

[Govmnt_Lacky]

Is this the correct orientation?

As I look at this picture... if you are using PNP silicon transistors (2N3906)... then your transistors are installed WRONG. Looking at this picture, both of the transistors need to be turned around. Q1 needs the flat side facing the Electrolytic cap. Q2 needs the flat side facing the trimmer.

Good Luck 

[texstrat]

Q1
C - 8.00 mV  Grounding the emitter may bring this voltage nearer to 1/2 of supply.
B - 8.83 mV
E - 9.45 mV  This lead should connect to ground = 0.0v.

Q2
C - 4.15 mV
B - 8.00 mV
E - 8.66 mV
  Q2 bias may be getting thrown off by Q1E's no ground situation.

Peter:
You will have to forgive my ignorance, but how would I go about grounding the emitter? Based on the schematic the emitter side for both are supposed to go to ground.
To reiterate, this is a GGG Fuzz Face using the PNP transistors and positive grounding.

[Govmnt_Lacky]

Sorry for my quick response  

After examining the schematic, if you are using 2N3906 transistors then you have them oriented correctly. Q1 flat side should face Q2, and Q2 flat side should face Q1.

Very sorry for that sir!  

[Jhouse]

Q1
C - 8.00 mV  Grounding the emitter may bring this voltage nearer to 1/2 of supply.
B - 8.83 mV
E - 9.45 mV  This lead should connect to ground = 0.0v.

Q2
C - 4.15 mV
B - 8.00 mV
E - 8.66 mV
 Q2 bias may be getting thrown off by Q1E's no ground situation.

Both of the transmitters do end up going to ground though, Q1 directly and Q2 from the 1k lin pot. Hmmm. Have you checked all of your solder joints?

I guess you could connect the emitter leg of Q2 directly to ground. Also, make sure that you have the DC jack and battery clip wired up correctly.

[texstrat]

It seems like the part of the board where the wires come in from the pots is screwed up. I run the audio probe along the pots and get the good voltage until I get to the contour pot and the voltage is zero or very close. I replaced the wires and still the same low voltage. Then checking the 1K and 33K resistors, I get good voltage on the transistor side, but on the pot side I get zero on voltage, this is per the layout page for the build. Anyway, I have spent too long screwing with this and very frustrated to boot! 13 components and 10 wires coming into the board, it should not be hard.

I have learned quite a bit about debugging and diagnosing, so it had not been an entire loss.

[Joe Hart]

Keep at it. I've debugged stuff and found the problems to be (among other things):

I had the guitar cord in the output and the cord going to the amp coming from the input (hours of debugging)
A fried IC (I gave up on this, pulled the IC out for another project and discovered it was no good)
Transistor pinouts wrong (too many to count)
Fried transistors (a few)
A bad capacitor that took FOREVER to figure out
A bad guitar cable (yup!)

So keep at it. Many times it's something simple and/or silly! Hope this helps.
-Joe Hart

[Hides-His-Eyes]

Unless you've used some kind of standoffs, then all your solder joints are grounding into the enclosure.