Making sure the transistors are dead

Started by The Rocket From The Tombs, December 29, 2012, 02:26:54 PM

Previous topic - Next topic

The Rocket From The Tombs

The pedal I'm building is a GCB-95 wah wah pedal with the buffer removed and I'm troubleshooting the board with an audio probe.
Everything makes a buzz except these two transistors. Here's a layout of the pedal with the pads on each tranny that are unresponsive colored in red with some green in the middle. The transistors themselves are outlined in purple. Since the pads that aren't buzzing aren't connected to anything else, maybe this is normal? Anyway, before I replace them I just wanted to get a 2nd opinion on whether you think these are bugged. Also, the probe buzzes even when I put it on a ground connection, is that normal? Thanks.

TL;DR: Two transistor connections colored in red n green don't buzz when touched to audio probe, is this normal? 

http://www.use.com/70ddf15d3cef5623ff0e



armdnrdy

I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

pinkjimiphoton

wow, you're still working on this?

let me make a suggestion?

start over. begin with a WORKING design.

once you get YOUR build working, then mod it, if needed.

starting cold with a project pre modified by you is a recipe for disaster. i remember spending like, a week or two trying to help you with this before.

not picking on you, but man, you're just setting yourself up for heartache.
  • SUPPORTER
"When the power of love overcomes the love of power the world will know peace."
Slava Ukraini!
"try whacking the bejesus outta it and see if it works again"....
~Jack Darr

The Rocket From The Tombs

#3
Oh no man, if I'd been working on it straight I think I would've driven myself nuts, I put it on the shelf for a few months and just picked it back up today. For the audio probe, mono jack with this capacitor http://www.newark.com/epcos/b32529c104j/capacitor-poly-film-film-0-1uf/dp/26M8219?Ntt=26M8219   I just soldered the probe to ground instead of using alligator clips.

LucifersTrip

#4
Quote from: The Rocket From The Tombs on December 29, 2012, 02:26:54 PM

Everything makes a buzz except these two transistors.  Anyway, before I replace them I just wanted to get a 2nd opinion on whether you think these are bugged



this is no different than troubleshooting any other pedal. check out the schematic, find or ask for working voltages of the transistors and compare with what you have. the voltages should help pinpoint a wiring or transistor problem.


always think outside the box

slacker

The question is why aren't they connected to anything? There should be connections to all the transistor legs.

The Rocket From The Tombs

Really? I just followed Dunlop's layout for the transistors. See, those pads on the original layout are islands: http://www.use.com/7b9d981dabea22976f65

slacker

There's other places where there's pads that don't appear to go anywhere, like the 390 Ohm resistor on the left hand side is only connected at one end, which makes no sense. Are you sure that's not supposed to be a double sided board, with more connections on the other side.


pinkjimiphoton

dude, like i told ya months ago...and not to be a buzzkill...

but what you came up with and "modified" just plain ain't gonna fly.

you don't even have a circuit...no continuity. you'lll bang your head against a wall for years, and never get it to work.

you have parts misplaced, you have crucial connections that aren't hooked up (like the transistors)..

seriously. start over, use something that WILL work, and once you have it working, then mod it.

the layouts you post are no help to us here...we can't help because there's no schematic to work with, as you "based" your design on other stuff.

i remember going thru this months ago with you...it plain ain't gonna work, you have the circuit open in several areas.

you'll do yourself a favor sometimes abandoning a flawed project, and doing something that will work.

never go for the Blind Urge to Mod.... especially modding a circuit that you've never built before. seriously. not trying to be a dick at all, but
you're still chasing the same dragon.
  • SUPPORTER
"When the power of love overcomes the love of power the world will know peace."
Slava Ukraini!
"try whacking the bejesus outta it and see if it works again"....
~Jack Darr

slacker

Quote from: The Rocket From The Tombs on December 29, 2012, 04:18:03 PMReally? I just followed Dunlop's layout for the transistors. See, those pads on the original layout are islands: http://www.use.com/7b9d981dabea22976f65

The photo you posted is pretty helpful, this layout is wrong. The two pads that look like islands on the transistor on the right should be connected to the pads right next to them. The island pad on the one on the left should be connected to the trace directly below it.
Looking at your layout those same corrections would make those parts match a typical wah schematic. The rest of it could still be utter gash though.

Edit: posted the same time as Jimi, what he said chuck it away and start again, from known to be good schemos and layouts.

The Rocket From The Tombs

#11
I understand, although if I'm gonna do it 100% right this time I gotta find a layout that's right. The layout I posted was the only one I could find  and I'm terrible at reading schematics.

EDIT: If I did re-use this layout, what's wrong with it that I'd need to change? http://www.use.com/049a23db98724f1119ff
This was where I originally took the layout from, the only one I could find:
http://www.use.com/5eb7e202fe47e03ea69a  On here, they show those pads as islands, I'm assuming this layout is wrong?


pinkjimiphoton

hard to tell just looking at an unpopulated pcb trace layout.

you're gonna etch your own pcb? try and find a verified layout. don't look on that picture sight, look in the layouts gallery here.

one of THE guys to go to would be probably Joe Gagan. pretty sure RG Keen has layouts on geofex.com too.
  • SUPPORTER
"When the power of love overcomes the love of power the world will know peace."
Slava Ukraini!
"try whacking the bejesus outta it and see if it works again"....
~Jack Darr

pinkjimiphoton

check out the wah2 layout that comes with diylayoutcreator.
  • SUPPORTER
"When the power of love overcomes the love of power the world will know peace."
Slava Ukraini!
"try whacking the bejesus outta it and see if it works again"....
~Jack Darr

pinkjimiphoton

  • SUPPORTER
"When the power of love overcomes the love of power the world will know peace."
Slava Ukraini!
"try whacking the bejesus outta it and see if it works again"....
~Jack Darr

armdnrdy

Jimi,

You're the man!

I was just going to suggest that in "making sure the transistor is dead" to smash it with a hammer! That way we will be sure that it's really dead!
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

pinkjimiphoton

lol...hi larry.

i just hate to see this guy dick around with this and never get it to work.  i wanna see him succeed!!   :icon_mrgreen:
  • SUPPORTER
"When the power of love overcomes the love of power the world will know peace."
Slava Ukraini!
"try whacking the bejesus outta it and see if it works again"....
~Jack Darr

The Rocket From The Tombs

Haha, thanks guys. So, I figure my options are learning to read the schematic myself, finding someone else to translate it into a layout, or finding a wah pedal that sounds similar or I like better, to the GCB-95, that already has a layout on the internet.

armdnrdy

Quote from: The Rocket From The Tombs on December 29, 2012, 10:42:52 PM
Haha, thanks guys. So, I figure my options are learning to read the schematic myself, finding someone else to translate it into a layout, or finding a wah pedal that sounds similar or I like better, to the GCB-95, that already has a layout on the internet.

Jimi found the layout for you! He posted it! You must learn to keep your eyes peeled!

http://www.tonepad.com/getFile.asp?id=114

Schematic, layout, PCB file all in one nice little package!
Now thank Jimi!
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

The Rocket From The Tombs

oh WOW, how did I miss that! Thank you Jimi. I know you said to start off with, no mods but, what about using the fasel inductor? I'd like to salvage that part.