First timer in need of help with BMP project.

[jfishbein]

Hoping someone might be able to help me out.  I just started my first DIY project and i need advice.  In the process of populating and soldering the capacitors and i had a teeny, tiny yellow .0039 mF capon my board.  When I put it on and pulled the leads through, it cracked in half.  the spacing of the holes on the pcb were a little too wide for the cap.  Can I replace this with a cap of a different value?  What kind of difference will this make?  This is a kit from GGG. The cap in question goes in C10.

Thanks in advance for all of your help!

[blooze_man]

You can use a .0047uf cap in its place, or any cap that's close in value. There should be no percievable difference in sound.

[twabelljr]

I agree. Look for a .0033 or .0047. These are very common values and if you cant buy them locally, chances are very good you can find one (or more) in an old electronic component that is no longer being used or broken. The value markings will be 332 or 472. You may get lucky and find a 392. If you don't have any old equipment, ask around. Most people are happy to get rid of them. You will score tons of good film and ceramic caps

[jfishbein]

Thanks for all of your help. I was able to find some .0047pm caps at rat shack, so I think I will try those out. There size is a little bit larger though, should I be worried? Also, while I'm asking, if a small piece of the ceramic cap right around where the lead comes out, has broken off, will that affect the piece and/or the integrity of the circuit?

Thank you once again for all of your help!

[edvard]

If you have a burnt-out CFL bulb, every one I've ever torn apart has a .0039uf cap in it, and it's always on long leads.
Give it a shot.

[jfishbein]

Thank you all for your help, it is very much appreciated. Have it all together, but as it is only working in bypass I believe I'm going to have to begin the debugging process. From what I've read this seems to be a DIY'ers rite of passage. In any event, I'll be getting out my magnifying glass, multimeter, and throwing together a signal tester and getting to work. I'll let you know how it goes...

Oh, and one more time, thank you!

-Joshua

[newfish]

Thank you all for your help, it is very much appreciated. Have it all together, but as it is only working in bypass I believe I'm going to have to begin the debugging process. From what I've read this seems to be a DIY'ers rite of passage. In any event, I'll be getting out my magnifying glass, multimeter, and throwing together a signal tester and getting to work. I'll let you know how it goes...

Oh, and one more time, thank you!

-Joshua

Good luck with your BMP.  It's a hell-of-a-thing once working.

The single most valuable thing I've ever put together was an Audio Probe.
Once I've established that supply voltage is present where it's required on the PCB, the Audio Probe is my next step - it'll help you trace through the signal in the circuit from the jack socket - all the way through to wherever the signal stops. 
A quick search on this forum should bring up info on making one.
---
Or you could solder a standard 1/4" jack plug 'as normal' (Signal at the tip, Ground at the sleeve) at one end of your cable.

...and at the other end, solder a small crocodile clip to your Ground wire.
Solder one leg of a small capacitor (47nF, for example) to the 'signal' wire. The other leg should be left unconnected.

Plug the 1/4" plug of your Audio Probe into a test amplifier, and clip the croc.clip onto your PCB's ground (chassis, if it's boxed, or clip to a ground lug on your output socket, for example).

With a test signal (a low-volume walkman / MP3 play back) connected to your FX input socket (as your guitar would be), you can now touch the unconnected leg of your Capacitor to various points of your PCB to see if a signal is present.

Having a schematic printed out next to you is invaluable at this stage.

Hope that sort of made sense.

Cheers,

Ian.

[jfishbein]

So I ended up replacing the .0039 mF cap in C10 with a .0047 mF (472k on ceramic cap) and still nothing.  Only sound when bypassed.  I checked all of the wiring and everything follows the wiring diagram from GGG.  I used a magnifying glass to look for any bridged solder joints, but everything seemed okay.  I tested the battery I was using and I got 9.6v.  I tested the voltage at the transistors and I got readings as follows (measurements given by GGG in parenthesis):

Q1
C 3.84    (3.9)
B 0.62    (0.6)
E 0.037  (0.03)

Q2
C 4.14    (3.
B 0.65    (0.6)
E 0.053  (0.03)

Q3
C 3.83    (3.
B 0.62    (0.6)
E 0.035   (0.03)

Q4
C 4.71     (4.0)
B 1.876   (2.5)
E 1.297   (1.

Are the discrepancies in the measurements indicative of there being an issues in one of those areas?

Suggestions?

Thanks again.

[jfishbein]

 So I built my audio probe and began testing through the circuit and low and behold the signal flowed through the entire pathway. I was shocked that it was working. I plugged my guitar in and voila! Signal. Maybe I was doing something wrong, don't know, but it works now. The only thing I noticed was that the LED was not working so I replaced it with a nice green one. Then I closed her up and I completed my first pedal!

Newfish, you were right, this pedal sounds great now that the bugs have gone.

Thank you to everyone for all of your help here. It is much appreciated.

-Joshua

[petemoore]

Q1
C 3.84    (3.9)
B 0.62    (0.6)
E 0.037  (0.03)

Q2
C 4.14    (3.
B 0.65    (0.6)
E 0.053  (0.03)

Q3
C 3.83    (3.
B 0.62    (0.6)
E 0.035   (0.03)

Q4
C 4.71     (4.0)
B 1.876   (2.5)
E 1.297   (1.

  And there you have it ! ! Base above emitter by about a diode drop, collectors pretty much middlin' voltage with room to swing room +/- .
  When this circuit fires up it tends to burns strong, 4 transistors and associated peripheral components...a long string of gain stages within 9vdc supply, I think that may have been a priority of the design goal/achievement, and a big part of what makes it cool.
  A few more parts but when it goes right it should make just about any Highish gain transistors work [distort hard, run TC, and boost] just about any SC pickup.