GGG Big Muff Debug Help

[Freekmagnet]

Hi,

I'm pretty new to electronics, so any advice would be appreciated.

So, I'm building a GGG Tuned Big Muff using the GGG PCB. Light turns on, but there's no sound. Using an audio probe, I have trace the signal from the output jack and I seem to have a signal all the way up to the base of Q4. After that, no sound on either side of the transistor. Using my multimeter, there seems to be continuity coming from either side of the transistor. I double checked and the transistor is oriented as indicated by the layout.

Help. SOS. I'm lost in the woods.

[R O Tiree]

Could you measure the voltages on the pins of Q4?

They should be something like:

C +4.0V
B +1.8V
E +1.1V

If you're able to trace the signal as far as Q4's base, then there are only about 4 or 5 more components where a fault could lie. Have a good look at the 4 resistors around Q4, the output cap and the volume pot. Check for shorts to other tracks and dry joints. Check that none of the blobs of solder on the pot lugs are touching.

[Freekmagnet]

Thanks. I'll measure those voltages and double check my connections sometime over the weekend.

Here's one thing I just thought of on my way to work - I did change the resistor (R27) that goes to the LED. I don't have my notes indicating it's value with me, but I got the value from one of those online resistor calculators. The new LED is blue, which I read takes more juice than a red one. Is it worth my time to investigate this as a possible problem? If so, could I just disconnect the LED or should I replace the whole thing with the red light and the stock resistor?

[Freekmagnet]

So, I got my readings on Q4, and now I'm even more lost...

C = 9.0v
B = 0.8v
E = 9.0v

Q4 seems to be getting the full power of the battery. I checked R24 and it seems to be the 10K that is called for on the layout. Am I measuring this incorrectly? I have the black lead of my Multimeter to ground and I'm probing the legs of the transistor with the red end. It's set to 10 DCV and when I touch it to my battery it reads 9v.

Any suggestions?

Thanks,

Jeremy

[petemoore]

  Check the emitter>resistor>gnd. 'circuit.
  From transistor lead to some 'distant point' [battery clip?].
  Might as well clip that black lead on Gnd. and test every ground [they should all 'beep'], see if the ground lead of the E resistor on Q4 is Gnd., then set the DMM to R 20k range, and see what that little emitter resistor is doing.
  If it's less than 2k set meter to 2k for closer reading, but we're just looking for a little resistance, about the value of the schematic here.
  It seems the emitter is 'floating'.

[Freekmagnet]

Hey, thanks for your help guys! I figured it out and it works. The resistor leading into to collector was wrong. I read the bands backwards! I guess that teaches me that I should never assume that a component that comes with a kit is correct and that I should measure everything before I put it in the board.

Anyway, here's a couple of photos. I posted a few more at the byoc forum.

Thanks again!

[Barcode80]

 

How did  you do that great finish?!?!

[80k]

yea that finish is fantastic!
What's with the caps with really long leads going into those sockets?

[R O Tiree]

VERY cool paint-job. Glad you found the snag as well.

As to the socketed caps... Tone Stack mod?

[Freekmagnet]

Thanks, guys. I'm really happy with the finish, too. I'm sort of a decal and finish nut. I've been perfecting my technique. I just got to work on my wiring a little more!

Anyway the caps - I'm a bass player. I read about a mod on the GGG site that call to replace the caps going into the diodes to get a better bass response. I socketed them just in case I wanted to swap 'em out for some bigger ones. I left the leads long so that if I decided to reuse the old ones, it would be easy.

As it turns out, this pedal has great bass response as is. However, I think that fuzz in general just saps the attack from bass. I'm looking to find a good blend/loop circuit, so if you have any recommendations, let me know. I'm looking at the B.Blender and the Bass Paralooper at moosapatamus.

Anyway, thanks again for the kind words.

[Barcode80]

I need more detail on your finishing technique...

Anyhow, it doesn't get better than the B.Blender for a blend circuit.

[Freekmagnet]

I need more detail on your finishing technique...

Basically, I put a white undercoat on the top of the enclosure. Then I print swatches on the clear decal paper to match the overall paint color. After applying the decal, I cut the overlap where the paint color meets the decal with a razor blade.

I might post a photo tutorial next time I do one like this. It's time consuming, but not as hard as it sounds. It might be a while, 'cuz the next couple of builds I have planned are going to be a little more simple graphics-wise.

[Barcode80]

To be honest, I'm more interested and blown away by your clean clear coat process...

[Freekmagnet]

The clear coat is just Rustoleum clear spray lacquer. I give it about 3 - 5 really thin coats applied about 15 - 20 minutes apart. Really thin meaning one or two passes with the spray can. I cover the enclosure with a shoe box that has a 25w bulb inside of it to let the paint bake a little bit. Let it dry 24 hours. Wet or dry sand starting with 320 grit and work my way down to 1500 grit sandpaper. I have a little square of wood about 1.25" x 1.25" that I use as a sanding block. Don't skip grits and wipe it down with a tack cloth between sanding. Lastly, I polish it with Turtle Wax rubbing compound that I bought at Wal-Mart.

It's time consuming, but with a little patience and effort, you can get good results. The real key is the thin coats of paint. If it's hard to wait 15 min in between coats, just spray it go and have a cup of coffee and then go back and spray again.

[Barcode80]

Thanks! Yeah, I have patience issues, but I've been building for other people more and more and I need to perfect my clear technique. last question, where'd you get that black switch washer?

[Freekmagnet]

I bought the washer at my local mom & pop hardware store. They have a drawer of nylon washers. I found some black rubber ones at another local hardware store in the lamp parts section.

The clear coat thing is to just be methodical about it. If necessary, work on another project while the clear coat dries. I usually sand, prime and paint 3 or 4 enclosures at once so I'll always be staggering the paint process.