SOLVED Sandspur fuzz - no sound, led and bypass work

[Jedijedd]

Hello all,
This is my first post here, and probably like many new members, I have a troubleshooting question as my first post. I put together a Sandspur fuzz and have been getting no sound from the pedal. I get signal in bypass and the led works but nothing from the pedal itself. Interestingly enough, it produced sound on my first try, but the led was very weak and so was the sound. I’m not sure if there is a grounding issue or something is wired wrong.

Some of the troubleshooting things I have tried:
- tested all the values of caps and transistors which seem fine.
- tested the sweep and value of the pots which seem fine.
- tested the input jacks and footswitch
- tried different transistors with no change
- checked that I haven’t switched the input and output cables
- checked for grounding issues such as cold solder joints, bad solder joints, or bridges (I know some of this is not the prettiest but I’ve done the tug test and continuity test, however I could be testing these things wrong?)
-I replaced C3 with a new cap, as I wasn’t getting a reading but nothing has changed
- checked for any grounding issues such as metal touching the enclosure or foot switch

Things I haven’t tried or been able to figure out:
- getting correct measurements from the diode (I get a reading one way but not the other) or the electro caps. I haven’t removed them yet to get correct readings. I get values but they seem all over the place
- I haven’t been able to bias the transistors yet

I also wasn’t sure about my power supply. I have two wall warts that are center negative but one says ac/dc adaptor while the other says simply “dc”. I grabbed one thinking it was the dc one and wasn’t sure if I fried anything.

Anyway, I have been trying to get this to work for a few weeks, while also taking my time with it. This is my second pedal I’ve built, and the other one had the wrong value cap keeping it from working. I’m sure I am missing something simple here and hoped that another set (or sets) of eyes could help.

Thanks for looking and reading!

 

[Jedijedd]

Hard to really tell but from your photos it really looks like your power jack is wired backwards.. have you confirmed your getting positive voltage and not negative 9v?

I'll hook it up today and let you know. I have the positive wire going to the long leg on the jack. I'll see if I can get a better shot of the jack. Thanks!

 

[swelchy]

I'll hook it up today and let you know. I have the positive wire going to the long leg on the jack. I'll see if I can get a better shot of the jack. Thanks!

the long leg of jack is where the positive hookup goes.... but it would nt hurt to verify with multimeter... I make it a habit to spin the jack so the leg aligns with the left side of pcb.. positive on left and negative on right that way the pcb and jack are in alignment. and my wires go straight to them without having to cross and get messy

 

[Jedijedd]

the long leg of jack is where the positive hookup goes.... but it would nt hurt to verify with multimeter... I make it a habit to spin the jack so the leg aligns with the left side of pcb.. positive on left and negative on right that way the pcb and jack are in alignment. and my wires go straight to them without having to cross and get messy

That totally makes sense, thanks. I’ll test it today and see what comes up. I really didn’t like working with the cloth pushback wire. It’s had to see if things look okay after soldering, so I might change some of the wire with more conventional wire.

 

[Jedijedd]

Success!
Well, there is sound and it sounds like fuzz. Changing the r4 spot did the trick. I only tested it with the probe and then to see if I got sound through the amp. I haven’t put it back in the enclosure yet as I want to recheck all the wires and solder joints before putting it back in.

A few things:
-I am getting 9v power at the dc jack
-the values came up significantly for q2 but not q1 when testing the collectors with the multimeter. I would need to get the exact numbers for reference, but should they be similar?

Thanks again for all the help!

 

[Coda]

Success!
Well, there is sound and it sounds like fuzz. Changing the r4 spot did the trick. I only tested it with the probe and then to see if I got sound through the amp. I haven’t put it back in the enclosure yet as I want to recheck all the wires and solder joints before putting it back in.

A few things:
-I am getting 9v power at the dc jack
-the values came up significantly for q2 but not q1 when testing the collectors with the multimeter. I would need to get the exact numbers for reference, but should they be similar?

Thanks again for all the help!

What are the readings on the collectors now? With the positive probe on the collector and the negative probe on a ground point (input/output jack)…

 

[Feral Feline]

For your second pedal, you're doing great!

What with posting pics, and the trouble-shooting steps you've already taken, to diving into the schematic. Impressive.


As an aside, I'm really digging your avaguitar — something gold-foil in the neck, but what's the pup in the bridge position?

 

[Jedijedd]

What are the readings on the collectors now? With the positive probe on the collector and the negative probe on a ground point (input/output jack)…

I’m getting 1.28 at q1 and 4.01 at q2. It sounds great and I haven’t biased it yet but I would like to get this right all around.

For your second pedal, you're doing great!

What with posting pics, and the trouble-shooting steps you've already taken, to diving into the schematic. Impressive.


As an aside, I'm really digging your avaguitar — something gold-foil in the neck, but what's the pup in the bridge position?

Thank you so much! Even though I don’t completely understand the ins and outs of it all yet, it’s really satisfying to play something you made.

Thanks very much as well! It’s a 2011 fender blacktop. I made the pickguard by hand from a celluloid blank (it took forever, but that’s another story) and the pickups are indeed a gold foil in the neck based on a guyatone foil by a builder in New York called Gemini pickups. He also made the bridge pup and it is his version of an old valco lap steel pickup. I was going for a coodercaster of sorts. I put Flatwounds on it and it absolutely sings!
For anyone who’s interested, this is the front of the pedal (yep, I sure did paint the in and out arrows backwards…). What can I say, I dig pink and the pink panther…

 

[Feral Feline]

Super cool-for-cats, guitar and pedal!

PINK!

 

[Jedijedd]

I did a bit of reading for silicon fuzz and read that around 1.5v for Q1 is suggested. Looks like I’ll just tweak it a bit to get it around that and 4.5v on Q2. Thanks again for all the help! Looking forward to future builds!

 

[Jedijedd]

Well, it’s not working again.

It’s been sounding and working great and then just stopped working. Ironically, the led is on but no sound. I traced it again with the audio probe and soldered a one ground wire that didn’t have the greatest connection. I also changed the led and made a better mechanical connection to the wires and led itself.

I’m a bit stumped. What might cause it to just stop working? I haven’t changed anything in my setup. I haven’t broken out the multimeter yet.

 

[Harry Klippton]

Bad solder joints. Sockets

 

[Jedijedd]

I’ve gone over the solder joints a few times but will do so again. By sockets do you mean the pcb sockets?

 

[Harry Klippton]

If your transistors are in sockets and not seated well

 

[Jedijedd]

If your transistors are in sockets and not seated well

I think this may be it. One of the pins seems a bit loose. Thanks I’ll give that a try!

 

[Jedijedd]

It was one of the sockets. I guess it came loose when I was switching transistors. Thanks again.