Wylde overdrive vero troubleshoot

[cgibsong002]

Project based on this vero: http://www.aronnelson.com/gallery/main.php/v/Renegadrian/MXR+ZW44+-+Zakk+Wylde.gif.html
Moved the bottom leg of R6 up one to simulate minimum gain, put a trimpot in place of the tone pot, which leaves me with a single volume pot (I'm currently using a 100K instead of 10K) I also added a second diode in series with the left most diode for asymmetrical clipping true to the original.

IC is an RC4558P and the trans is a MPSA-14

1. The pedal turns on and applies a minimal amount of gain, as it should. with volume maxed, the volume is about as loud as the bypassed signal. there is no increase in pinch harmonics or sustain => this is where the problem is

2. Voltage on DC Jack terminals= 9.47V (using a one spot supply)

Q:
c: 9.47V
b: 4.51V
e: 3.94V

IC:
1: 4.83V     8: 9.43V
2: 4.83V     7: 4.78V
3: 4.78V     6: 0V
4: 0V          5: 4.78V 


D1:
A: 4.84V
K: 4.60V

D2:
A: 4.60V
K: 4.84V

D3:
A: 4.84V
K: 4.84V

Where D1 and D2 are the left most diodes in series, both with bands pointing in the downwards direction
and D3 is the righter diode pointing in the upwards direction.

[cgibsong002]

bump? no one else built this?

[Govmnt_Lacky]

Definitely a problem around Pin 6 if the 4558.

Try looking around there. It should be about the same as Pins 1-3, 5, and 7.

[cgibsong002]

I hate working on pedals! 
I haven't had a chance to work on this for a while, just picked it up today. Now the LED won't turn on. I accidentally discovered it will turn on if I ground the left-most diode. I'm trying to make sense of this but I can't figure it out, I haven't worked on circuits in a little while and I'm really scratching my head here. It doesn't appear anything is contacting something it shouldn't. Anything you guys could think of here or is it something you can't really help without seeing it?

[cgibsong002]

any possible thoughts? i must be missing something simple here, because it doesn't seem to make sense that grounding a component of my circuit would effect the (what should be separate) LED circuit. does it seem more likely to be a fault with my effect circuit or a ground elsewhere in the pedal or switch?

[DavenPaget]

I hate working on pedals! 
I haven't had a chance to work on this for a while, just picked it up today. Now the LED won't turn on. I accidentally discovered it will turn on if I ground the left-most diode. I'm trying to make sense of this but I can't figure it out, I haven't worked on circuits in a little while and I'm really scratching my head here. It doesn't appear anything is contacting something it shouldn't. Anything you guys could think of here or is it something you can't really help without seeing it?

Well , then ground the left most diode , i believe there's broken trace .

[petemoore]

  THe Led Circuit for true bypass w/3pdt is the same as debugging a flashlight [+1 current limiting R], power supply lights the bulb directly when the switch is closed. Difference being that everything is 'open' and easy to probe and inspect, unlike a flashlight.
   Verify the trace using beeping-DMM-mode or just follow voltage from battery through to the LED or Resistor, follow the other side of the battery [tracing or just measuring for voltage/no voltage drop] through the switch to the other side of the LED/R circuit.
   You should be able to find connection/traces which place the battery +voltage potential to the LED/R circuit, then -voltage to the other side of the LED/R circuit [depending on the switch and its position, which can also be measured/tested].
     

[cgibsong002]

sorry.. forgot to mention. i had changed the circuit to two diodes assymetric to the diode next to it. so it was initially kind of messy with the two diodes in series across parallel traces. so yeah my initial thought was something was up there.. but i moved them to an unoccupied set of traces on my board and jumped to the original traces.. but i'm still getting the same problem. so it can't be something with those themselves.

i just remembered, when i was probing voltages. i had 9 at power, a voltage across the led, but no voltage across the resistor. I'm kind of confused by this. clearly something is up with no drop across the resistor. but if there's a change across the led, shouldn't it be lit?

man.. this is what happens when i don't work on circuits for a while 

[cgibsong002]

ok got things working again. somehow my ground coming from power wasn't grounded with the rest of my commons.. so just ran a wire from the power negative terminal to my common. why it was working before and stopped i don't know. but it functions as it did before now.

so i'm still trying to troubleshoot why this thing doesn't act as it should. I believe I measured wrong before, here's my measurements:
IC:
1: 4.83V     8: 9.48V
2: 4.83V     7: 4.78V
3: 4.78V     6: 4.78V
4: 0V          5: 4.78V

I have very little practice troubleshooting problems at this stage... but I'm thinking its simply my R6 value that is messing with my desired results. The pedal works, I get a very slight volume and grit increase, but not as much as I should, and I've tried different IC's. It seems to me the only thing messed up would be the distortion path. What I was recommended to do with R6 seems correct to simulate minimum gain.. but maybe something with the original pedal had more resistance through there. Does it seem like I could be on the right path? Maybe try something higher like 100K for R6? I'll try it out..


EDIT: Ok.. I'm starting to just think that original pedal I had was magical. I tried out a 100K and a 220K in place for R6. By the time I tried the 220K it was adding on a decent amount of gain and volume.. but the harmonics and sustain just really weren't all that affected. It sounds really nice and is a nice way to add gain to my amp, but I'm not finding that sustain. Diodes maybe? I can't possibly think of what else, maybe op-amp? Volume is there, distortion is there, tone is good, but where's the signature sustain??

[cgibsong002]

bump 

[cgibsong002]

up again. i've pretty much exhausted all my options for what i know how to do. does anyone know if theres a certain segment of this circuit that is more or less responsible for the sustain aspect ( i guess compression)? i'm really hoping for some help or else i don't have much choice but to just buy the real deal, but i certainly don't want to do that.

[Fender3D]

....man.. this is what happens when i don't work on circuits for a while 

Nope, this is what happens when you work on circuits "by numbers", without giving a shot at a schematic...
Then a little math is usefull...
Increasing R6 will increase the first op-amp's gain G=R6/R4
Messing with diodes will change distortion and sustain.

BTW
Zakk is a nasty spitter anywhere on stage... maybe he spitted inside his pedal too for mojo sake...

[cgibsong002]

....man.. this is what happens when i don't work on circuits for a while 

Nope, this is what happens when you work on circuits "by numbers", without giving a shot at a schematic...
Then a little math is usefull...
Increasing R6 will increase the first op-amp's gain G=R6/R4
Messing with diodes will change distortion and sustain.

BTW
Zakk is a nasty spitter anywhere on stage... maybe he spitted inside his pedal too for mojo sake...

LOL. yeah maybe i'll try the spit thing 

well yeah R6 being responsible for the gain was pretty much all i knew. OK, so the diodes ARE responsible for sustain. so then whats my problem? Theres not really anything in that loop there aside from the 3 diodes and R6. should I try different types of diodes? From what i've heard they can make subtle tone differences but I couldn't imagine they'd make such a profound change in sustain and dynamics.

[cgibsong002]

feel like i'm an arsehole for bumping continuously but still hoping i can get any ideas as I haven't a clue and I'm really eager to get this into my board.