[Debugging] Rat Clone

[elenore19]

Rat Clone pedal from tonepad.com
http://www.tonepad.com/project.asp?id=45
No parts substitutions or mods.

I have no sound when the pedal is engaged. Nothing. The pots don't have any effect on the nothingness. I have a bypass signal when bypassed.

The numbers-

IC
1-8.62V
2-0.496V
3-0
4-0
5-0
6-0.498V
7-9.14V
8-9.10V

Q1
C-0V
B-2.06V
E-9.14V

D1
A-0
K-9mv and decreasing

D2
A-0
K-0

D3
A-0
K-9.14V

I constantly am searching for solder bridges and cold solder joints. But as of now, I haven't found anything.


Any help is greatly appreciated. Thanks guys.

-Elliot

[petemoore]

IC
1-8.62V
2-0.496V
3-0
4-0
5-0
6-0.498V
7-9.14V
8-9.10V

  I forget the pin #'s on the Rat, compensated opamp.
  For signal to 'swing, the two inputs and the output.
  Pin4 is Gnd.
  The +/- inputs and the output pins are biased using the voltage divider as *1/2v reference. Check that the 2 equal value resistors are equal value [strung across the power supply rails R*R]. And that the 1/2v point at the divider center indeed holds at 1/2v...and that the R through which the input pin is held to ~1/2v bias poin has the correct value.
  Is the chip pin 1 at "`top-left" ie oriented correctly ?
 
   
Q1
C-0V
B-2.06V
E-9.14V
  The CBE looks to be typo = EBC, and I forgot what type of transistor is here [Jfet ?].

D1
A-0
K-9mv and decreasing

D2
A-0
K-0
  ...clipping diodes I suppose

D3
A-0
K-9.14V
  Power protection ?
  IIRC also...+ power rail goes to Pin 7 and appears to be doing so.

[elenore19]

  I forget the pin #'s on the Rat, compensated opamp.
  For signal to 'swing, the two inputs and the output.
  Pin4 is Gnd.
  The +/- inputs and the output pins are biased using the voltage divider as *1/2v reference. Check that the 2 equal value resistors are equal value [strung across the power supply rails R*R]. And that the 1/2v point at the divider center indeed holds at 1/2v...and that the R through which the input pin is held to ~1/2v bias poin has the correct value.
  Is the chip pin 1 at "`top-left" ie oriented correctly ?

  Power protection ?
  IIRC also...+ power rail goes to Pin 7 and appears to be doing so.

Um. I need help on which resistors to check. I'm new to serious debugging and could use some guidance...
Also, the pin is installed correctly.
IIRC?
I need help on all the lingo. Or at least a point in the right direction.

Thanks so much for your help. I can't wait to learn all this good stuff.

[petemoore]

http://www.generalguitargadgets.com/projects/17-distortion/92-rodent

  10k / 10k = the resistive voltage divider = R15 / R16.
  The two equal resistors provide 1/2V reference voltage.
  A 4.5v potential exists between Gnd. and 1/2v, another 4.5v between 1/2v and V+. The line by R1 [1 meg] pulls the - input of the Rat to 1/2v when idle, this bias allows signal to swing the input +/- of the bias point.
  This schematic shows a second voltage divider made of 10k/22k resistors for the Jfet Gate Bias reference. This will not be 1/2v, and is needed to pull the Jfet base up above Gnd. See GEO for Jfet bias info, Source above gate...In this case 10k source resistor probably sits this Jfet output around the middle of the supply voltage [1/2v], the gate a bit below that, collector, if not reading V+...connect it to V+ [lol.
  If you find `1/2v at the voltage divider, measure from one of the resistor legs to the `opamp - pin to see if there's about `1meg between them.

[ryanuk]

elenore19

petemoore's is excellent - but I have a few clarifications.

I sounds like you've wired it directly into a pedal chassis (i.e. you mention bypass)? How have you wired the pedal? Using DPDT, 3PDT, LED? What type of in/out jacks have you used? Are you confident of your wiring here? Some images would help.

Its rare that a circuit works 100% first go. Wiring it in to a pedal straight out only increases the possible areas to debug. If you're planning to make a few pedals, I would build a simple test rig. Mine is simply a sqaure of old MDF with in/out jacks, battery clip, power jack, and a junction block glue gun'd onto it. No bypass. Crude but an easy way to test a circuit and ensure its working prior to building it in to a pedal.

What method did you use to produce the PCB?
I ask this as if drawn with an etch pen, are you sure no connections/traces have been missed?

Have you double/triple checked the components i.e. that all the right values have been used, and that the IC, diodes, elec caps and JFET are the right way round.

Your first post suggest that you've used a bipolar transistor instead of a JFET (2N5458)?

When you engage the effect, is there any whistling or white noise?

Post some more info on the above.

RyUK

[thedefog]

elenore19

petemoore's is excellent - but I have a few clarifications.

I sounds like you've wired it directly into a pedal chassis (i.e. you mention bypass)? How have you wired the pedal? Using DPDT, 3PDT, LED? What type of in/out jacks have you used? Are you confident of your wiring here? Some images would help.

Its rare that a circuit works 100% first go. Wiring it in to a pedal straight out only increases the possible areas to debug. If you're planning to make a few pedals, I would build a simple test rig. Mine is simply a sqaure of old MDF with in/out jacks, battery clip, power jack, and a junction block glue gun'd onto it. No bypass. Crude but an easy way to test a circuit and ensure its working prior to building it in to a pedal.

What method did you use to produce the PCB?
I ask this as if drawn with an etch pen, are you sure no connections/traces have been missed?

Have you double/triple checked the components i.e. that all the right values have been used, and that the IC, diodes, elec caps and JFET are the right way round.

Your first post suggest that you've used a bipolar transistor instead of a JFET (2N5458)?

When you engage the effect, is there any whistling or white noise?

Post some more info on the above.

RyUK

Agreed. Bypass your switching/jack set up and just use alligator clips to your in/out and V+/G points on the board.  I never wire a circuit up into an enclosure before testing it out with aligator clips first. Saves about 90% of the headache with debugging, as the wiring is where the majority of your problems will come from.

Are you using the PCB from Tonepad, or doing this on perf/vero?

[elenore19]

http://www.generalguitargadgets.com/projects/17-distortion/92-rodent

  10k / 10k = the resistive voltage divider = R15 / R16.
  The two equal resistors provide 1/2V reference voltage.
  A 4.5v potential exists between Gnd. and 1/2v, another 4.5v between 1/2v and V+. The line by R1 [1 meg] pulls the - input of the Rat to 1/2v when idle, this bias allows signal to swing the input +/- of the bias point.
  This schematic shows a second voltage divider made of 10k/22k resistors for the Jfet Gate Bias reference. This will not be 1/2v, and is needed to pull the Jfet base up above Gnd. See GEO for Jfet bias info, Source above gate...In this case 10k source resistor probably sits this Jfet output around the middle of the supply voltage [1/2v], the gate a bit below that, collector, if not reading V+...connect it to V+ [lol.
  If you find `1/2v at the voltage divider, measure from one of the resistor legs to the `opamp - pin to see if there's about `1meg between them.

Alright, I'll look into it and make sure everything is the right way. Still a little confused, but I feel like once I sit down and work on this pedal things will make a lot more sense. Thanks!

elenore19

petemoore's is excellent - but I have a few clarifications.

I sounds like you've wired it directly into a pedal chassis (i.e. you mention bypass)? How have you wired the pedal? Using DPDT, 3PDT, LED? What type of in/out jacks have you used? Are you confident of your wiring here? Some images would help.

Its rare that a circuit works 100% first go. Wiring it in to a pedal straight out only increases the possible areas to debug. If you're planning to make a few pedals, I would build a simple test rig. Mine is simply a sqaure of old MDF with in/out jacks, battery clip, power jack, and a junction block glue gun'd onto it. No bypass. Crude but an easy way to test a circuit and ensure its working prior to building it in to a pedal.

What method did you use to produce the PCB?
I ask this as if drawn with an etch pen, are you sure no connections/traces have been missed?

Have you double/triple checked the components i.e. that all the right values have been used, and that the IC, diodes, elec caps and JFET are the right way round.

Your first post suggest that you've used a bipolar transistor instead of a JFET (2N5458)?

When you engage the effect, is there any whistling or white noise?

Post some more info on the above.

RyUK

Yes. I wired it up directly into the enclosure That's what I've been doing lately, and realizing that it is definitely poor practice. I am working on a little breadboard prototyping setup with jacks and such.
I use this wiring. I've triple checked it. But it can't hurt to check it again. Since it has bypass signal just fine I assume that I wired it all up correctly (the switch at least...)
http://gaussmarkov.net/wordpress/thoughts/wiring-up-a-1590b/
I'll post pictures.
I'm not sure of the method that was used for etching the PCB but I had a guy on the forums (Bill "bluesdevil") make me the board, he's made tons for me and they have always been real solid. So I really don't think there is an issue with the etching. I'll try and compare it to the PDF though.
I checked the polarity on my caps and also on the diodes. I also checked multiple times on the chip.
When I work on the boards I always make sure to be exactly correct on which part I'm using so I don't have to bother checking again. I'm 97% sure all the parts are correct. I'll try and double check, but that shouldn't be an issue.

I used exactly what tonepad said to use.
The transistor is a 2N5458. So I'm not sure if that's a jfet or bipolar. (I'm really terrible at this. I'm here to learn!  ) I just looked at the specific transistor in the board and that's definitely what it is. It's also oriented the correct way.

When I engage the pedal I didn't notice any white noise. It more sounded like the input was making contact with ground. Just no sound at all. Nothing. The knobs didn't cause any sort of scratchiness or anything of the sort. At least as far as I could notice.

Hope that helps! Thanks so much for the help!

Agreed. Bypass your switching/jack set up and just use alligator clips to your in/out and V+/G points on the board.  I never wire a circuit up into an enclosure before testing it out with aligator clips first. Saves about 90% of the headache with debugging, as the wiring is where the majority of your problems will come from.

Are you using the PCB from Tonepad, or doing this on perf/vero?

Yeah, I'm making a setup for testing boards right now actually...Haha. I plan on making tons of pedals, and it's evident that it's a must to wire it up outside first...
I'm using the PCB layout from Tonepad. I had the board etched by Bill "Bluesdevil".


Pictures:


A picture of the front, just for shits and giggles

[chromesphere]

Hi Elliot,

For me personally, 9 times out of 10 when the board is misbehaving, it's a solder bridge.  Dont know if you have checked for this yet, but i'd go around the tracks with a razor and a magnifying glass and give them a good scratch.

Hey nice graphics by the way.  Looks cool!

Paul.

[thetragichero]

Q1
C-0V
B-2.06V
E-9.14V
  The CBE looks to be typo = EBC, and I forgot what type of transistor is here [Jfet ?].

yes, n-channel jfet
could it be as simple as either a bad component (i had a similar problem with a 2n5457 that had me cursing and throwing things until i tried another one from the box) or needing to be biased?
we need to do a secret santa to send the OP a breadboard for christmas!

[elenore19]

Hi Elliot,

For me personally, 9 times out of 10 when the board is misbehaving, it's a solder bridge.  Dont know if you have checked for this yet, but i'd go around the tracks with a razor and a magnifying glass and give them a good scratch.

Hey nice graphics by the way.  Looks cool!

Paul.

Alright, really good to know. I'll look around for a razor blade
Thanks on the graphics compliment. A friend painted it for me. I have 5 artists painting pedals for me right now...I love having artistic friends that have nothing to do

yes, n-channel jfet
could it be as simple as either a bad component (i had a similar problem with a 2n5457 that had me cursing and throwing things until i tried another one from the box) or needing to be biased?
we need to do a secret santa to send the OP a breadboard for christmas!

I'll try and switch the component after I search for solder bridges.
I bought a tiny little breadboard the other day for 10 bucks. I have it hooked up and ready to go for trying out new boards in the future. With this one I'm just going to plug it out and see if I can fix it while in the enclosure.


Thanks for all the help guys! I'll keep you updated.

-Elliot

[chromesphere]

Alright, really good to know. I'll look around for a razor blade

HAHAHA!!  Too funny.

I know what you mean though, debugging gets a bit like that

Paul

[elenore19]

Alright, really good to know. I'll look around for a razor blade

HAHAHA!!  Too funny.

I know what you mean though, debugging gets a bit like that

Paul

Hahaha, yep.

ALRIGHT! NEW DEVELOPMENTS...

So I was dinkin around trying to figure out some problems and found when I connected two parts with my finger I got a sound.
So I created my very own solder bridge....It made it so the pedal sounds how I think it should sound. BUT the filter knob doesn't work. I have a feeling that has to do with the solder bridge I created. So does this mean a bad pot??
God damn, I feel SO close to getting this up and running.

Here's a picture of the solder bridge. It's where the big pink blob is...

[thedefog]

Alright, really good to know. I'll look around for a razor blade

HAHAHA!!  Too funny.

I know what you mean though, debugging gets a bit like that

Paul

Hahaha, yep.

ALRIGHT! NEW DEVELOPMENTS...

So I was dinkin around trying to figure out some problems and found when I connected two parts with my finger I got a sound.
So I created my very own solder bridge....It made it so the pedal sounds how I think it should sound. BUT the filter knob doesn't work. I have a feeling that has to do with the solder bridge I created. So does this mean a bad pot??
God damn, I feel SO close to getting this up and running.

Here's a picture of the solder bridge. It's where the big pink blob is...

If you bridged the connection where you marked it, it would bypass your filter pot completely. If you remove the bridge and it stops passing a signal, then it could be the pot is bad. That's not very likely, but I wouldn't rule that out. Best thing to do is check continuity with your meter and make sure you can pass a signal through that pot. Connect one end of your meter to Lugs 1&2, and the other to lug 3 and set it to Ohms and see if you get a reading on it. If you do, then the pot is in good shape, and there is something else funky going on.

Can you take a picture of the top and bottom of your board in better quality? that would definitely help.

[elenore19]

If you bridged the connection where you marked it, it would bypass your filter pot completely. If you remove the bridge and it stops passing a signal, then it could be the pot is bad. That's not very likely, but I wouldn't rule that out. Best thing to do is check continuity with your meter and make sure you can pass a signal through that pot. Connect one end of your meter to Lugs 1&2, and the other to lug 3 and set it to Ohms and see if you get a reading on it. If you do, then the pot is in good shape, and there is something else funky going on.

Can you take a picture of the top and bottom of your board in better quality? that would definitely help.

Checked the pot and got a reading with doing what you said. Checked and made sure that the resistors in that area read the correct amount of ohms, and I checked for continuity all around that area and from the board to pot etc. Everything checked out.
So the pot is good. What next?
Here are the best pictures I could get.
Hopefully I can get this figured out.
Thanks for all the help.

[chromesphere]

Um difficult to tell as the cap has two white bands but is that 4.7uf electro installed the right way around?

Also have you triple checked all other polarised components are the correct orientation?

Edit: apart from IC and tranny (and the cap in the middle of the board) everything else looks ok. 

Paul

[tubelectron]

Hi all,

What always amazes me are the graphics ... It's where I have bugs. Never in the electronics ! Always in painting, decals, durable finishes on stompboxes, etc...

[thedefog]

It doesn't make sense that it works with the bridge in place, but doesn't when removed if the pot is working. Check continuity of the wires running to the frequency pot. If it is good, then I'd use an audio probe to listen for where in the signal path the sound stops. Make one out of a 9v mini amp, or build the little gem from parts at Radio Shack if you don't have a battery powered amp. DO NOT use your real amp as a probe.

Did you take your photos on a mac? looks like they're inverted.

[elenore19]

It doesn't make sense that it works with the bridge in place, but doesn't when removed if the pot is working. Check continuity of the wires running to the frequency pot. If it is good, then I'd use an audio probe to listen for where in the signal path the sound stops. Make one out of a 9v mini amp, or build the little gem from parts at Radio Shack if you don't have a battery powered amp. DO NOT use your real amp as a probe.

Did you take your photos on a mac? looks like they're inverted.

The continuity of the wires going to the frequency pot is good. Maybe I'll try and new pot, and then go for the mini amp. I'm not sure how to make a mini-amp from parts at radioshack...And don't have a battery powered one...Any help?

-Elliot

[thedefog]

It doesn't make sense that it works with the bridge in place, but doesn't when removed if the pot is working. Check continuity of the wires running to the frequency pot. If it is good, then I'd use an audio probe to listen for where in the signal path the sound stops. Make one out of a 9v mini amp, or build the little gem from parts at Radio Shack if you don't have a battery powered amp. DO NOT use your real amp as a probe.

Did you take your photos on a mac? looks like they're inverted.

The continuity of the wires going to the frequency pot is good. Maybe I'll try and new pot, and then go for the mini amp. I'm not sure how to make a mini-amp from parts at radioshack...And don't have a battery powered one...Any help?

-Elliot

The pot is probably not your issue. Check the polarity of your electrolytic caps again. You may also be able to get away with using an old pair of headphones as your audio probe. I've done this before with overdrive/distortion circuits. Most the time there is enough gain after the opamp to lightly amplify a pair of headphones. Just don't wear them on your head while you're doing this unless you want to destroy your hearing with a nice pop if you accidently touch +9v.

[elenore19]

The pot is probably not your issue. Check the polarity of your electrolytic caps again. You may also be able to get away with using an old pair of headphones as your audio probe. I've done this before with overdrive/distortion circuits. Most the time there is enough gain after the opamp to lightly amplify a pair of headphones. Just don't wear them on your head while you're doing this unless you want to destroy your hearing with a nice pop if you accidently touch +9v.

Alright, so I switched out the pot just to see what would happen, and how the pot works great and I get signal through the whole pedal.
NEW ISSUE
There is signal loss. The pedal seems to be doing what it's supposed to, except it's a very weak signal. As in I can hear it with the volume pot cranked and my twin reverb turned up to about 7. Then it sounds how it should with the volume pot at 12'oclock and my amp at about 2.

Any suggestions? I'm having this problem with 2 other pedals as well, but that's another story.
Will the audio probe help this issue?