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Transparent Overdrive

Started by Hexjibber, January 26, 2014, 01:44:09 PM

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gingataff

That etch is proper bo. I hope you get it sorted.

m-Kresol

Quote from: Hexjibber on February 02, 2014, 02:25:01 PM

Thanks for the suggestion, I checked this and have continuity between input pad and ground pad, input pad and 2M2 but nothing between input and 510K. Continuity starts again between the 510K and pin 3 of the IC. I tried reflowing the solder on pads of the 510K but still nothing. I just can't seem to see where the input would be grounded via a short?


I'm still a beginner, but it strikes me as very wrong to have conducting connection between input pad and ground pad. Therefore, all your signal will be lost as it is basically going to ground (which every electrical signal wants to do) instead of through your signal path as you'd want it.
Check if you have a solder joint between these to pads, or if it really is supposed to be that way. Might be worth a shot!

Could you please post a link to the build doc, so I can have a look at the schematic?
I build pedals to hide my lousy playing.

My projects are labeled Quantum Effects. My shared OSH park projects: https://oshpark.com/profiles/m-Kresol
My build docs and tutorials

micromegas

Quote from: Hexjibber on February 02, 2014, 02:25:01 PM

Quote from: micromegas on February 01, 2014, 06:31:49 PM
I would begin by checking continuity between the IN pad and gnd, and then between the IN pad and the leads from the 2M2 and 510K resistors that are soldered to gnd (it seems that those are the pads at the left).

Could it be the GAIN pot the one that is shorting this resistors and therefore grounding your input signal?

Thanks for the suggestion, I checked this and have continuity between input pad and ground pad, input pad and 2M2 but nothing between input and 510K. Continuity starts again between the 510K and pin 3 of the IC. I tried reflowing the solder on pads of the 510K but still nothing. I just can't seem to see where the input would be grounded via a short?

Never had an issue like this before but it feels like something is staring me in the face and I can't see it!

Any ideas on how I could test for whether something is shorting?

Sorry for my mistake, I checked again and the 510K resistor goes from pin3 of the IC to Vref, not GNd...
But, certainly, the 2M2 resistor goes from input to ground, so, if you have gnd on both terminals of this resistor, or the resistor is broken, or there is a short in the tracks, or the short is happening outside the pcb (probably in the switch as lincolnic said).

I takes time, but what I usually do is follow the schem, from input to output, checking all the connections with the multimeter.

Or, if there is a short from in to ground, I'll start checking continuity between the main ground (on the DC jack) and all the supposed grounds in the circuit. Or to follow the tracks connected to the input till you find the short.

I bet there's people here that could be more helpfull as they have better experience with debugging.
'My favorite programming language is solder' - Bob Pease

Software Developer @ bela.io

micromegas

Quote from: m-Kresol on February 02, 2014, 03:44:48 PM
Could you please post a link to the build doc, so I can have a look at the schematic?

I assumed that it is based on a famous transparent od called something like "T(o)mmy"   ;)
'My favorite programming language is solder' - Bob Pease

Software Developer @ bela.io

lincolnic

Quote from: Hexjibber on February 02, 2014, 02:25:01 PM

Quote from: micromegas on February 01, 2014, 06:31:49 PM
I would begin by checking continuity between the IN pad and gnd, and then between the IN pad and the leads from the 2M2 and 510K resistors that are soldered to gnd (it seems that those are the pads at the left).

Could it be the GAIN pot the one that is shorting this resistors and therefore grounding your input signal?

Thanks for the suggestion, I checked this and have continuity between input pad and ground pad, input pad and 2M2 but nothing between input and 510K. Continuity starts again between the 510K and pin 3 of the IC. I tried reflowing the solder on pads of the 510K but still nothing. I just can't seem to see where the input would be grounded via a short?

Never had an issue like this before but it feels like something is staring me in the face and I can't see it!

Any ideas on how I could test for whether something is shorting?

Don't overlook the ground connections on your footswitch/input jack either. Like I mentioned before, a cold solder joint there has caused this problem for me at least twice.

Hexjibber

Hi guys, thanks for your suggestions, unfortunately I'm still no closer to figuring this out. Something is grounding the input but I just can't see what, I've checked and reflowed all my ground connections and tested them for continuity. I can seemingly only get so far following the tracks from the input point before I just lose where to go next, my newbie skills are hampering me somewhat!

It's a very well made pcb so sure it's not the culprit, I can only think I've got a duff component somewhere but am as yet unable to identify it. I can't see any unwanted solder joints, have been over it with a magnifying glass.

All in all very frustrating!

Jabulani Jonny

#36
Please post detailed, in focus shots of top and bottom of PCB. Please also post a shot of your switch and the jacks in the enclosure. Double check to ensure that a pot is not twisting when you tighten it and touching a lug to the enclosure. Pics will help, tremendously.

EDIT:  okay so the pots are board mount so no twisting and your switch and jacks look fine. Can you pull the PCB and take pics of the solder side? 
Electros properly oriented?

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Jonathan

Hexjibber

Quote from: Jabulani Jonny on February 04, 2014, 12:20:15 PM
EDIT:  okay so the pots are board mount so no twisting and your switch and jacks look fine. Can you pull the PCB and take pics of the solder side? 
Electros properly oriented?

Thanks for the reply man, will try and take a solder side shot tonight to see if that helps. I've checked and double checked the electros, as well as the diodes and IC.

I've got a real feeling I'm going to absolutely kick myself when I do get this working so I'm hoping it turns out to be something obscure that I never would have known about! ;)

Jabulani Jonny

Yeah, the wiring looks really clean and you've done plenty of pedals before so it's got to be something out of the ordinary.


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Jonathan

Hexjibber

Update on this, I started a thread on FSB and someone spotted I have a 2.2 OHM in R1 instead of a 2.2M and that is what will be causing the short. I ordered the wrong one from Banzai so was doomed from the outset, another lesson learned though!  :-[

Thanks to everyone who suggested things for me to try, pretty sure this will be the culprit though.

Cheers,
Graham

Jabulani Jonny

DOH!  Glad you got it figured out. Need a 2.2M?  I can a mail a few


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Jonathan

Hexjibber

Quote from: Jabulani Jonny on February 05, 2014, 03:28:42 PM
DOH!  Glad you got it figured out. Need a 2.2M?  I can a mail a few

Yeah it's a weird mix of relief and annoyance for which DOH! sums it up perfectly! ;)

Thanks for the offer man, that's very kind of you, I've got some on order already though! :)

raulduke

Cool build, and amazingly cool etch dude.

Really nice work!

Hexjibber

Quote from: raulduke on February 05, 2014, 03:35:32 PM
Cool build, and amazingly cool etch dude.

Really nice work!

Thanks man! :)

Bret608

Post again once you get it working and let us know how you like it! I did something similar on a Distortion + build. Should've been 1m, I used 100k. That's what I get for trusting my eyes to read those color codes!  ;)