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Projects => IC-based Overdrive => Topic started by: Otsismi on July 28, 2013, 10:35:20 PM

Title: Clean tone but no distortion(HELP)
Post by: Otsismi on July 28, 2013, 10:35:20 PM
I recently bread boarded the dod 250 IC circuit. When plugging into my amp I get a relatively boosted but clean signal from the circuit but no distortion or overdrive. The gain pot does nothing when turning. Can anyone give me some suggestions on why I'm not clipping?(http://img.tapatalk.com/d/13/07/29/me4y7ama.jpg)
Title: Re: Clean tone but no distortion(HELP)
Post by: mistahead on July 28, 2013, 10:38:33 PM
Did you check:
http://www.diystompboxes.com/smfforum/index.php?topic=79242.0

If not perhaps check out the debugging thread, voltages etc if you've got good electronics methodology/background already...
Title: Re: Clean tone but no distortion(HELP)
Post by: Otsismi on July 29, 2013, 04:38:26 PM
Why does changing the capacitor cause it to start distorting?
Title: Re: Clean tone but no distortion(HELP)
Post by: mth5044 on July 29, 2013, 05:00:44 PM
There seems to be some confusion with your layout.

The bus terminals are long strips, so the two red strips and the two blue strips are four long connections. You have those two long orange jumpers connecting... the same things. The large blue resistor isn't connected to anything. Your IC has no power going to it. The resistor on the bottom left next to the black probe isn't connected to anything. I'm very confused by your layout!
Title: Re: Clean tone but no distortion(HELP)
Post by: Otsismi on July 29, 2013, 09:42:49 PM
I'm confused about your assessment because I got it working last night.
Title: Re: Clean tone but no distortion(HELP)
Post by: mistahead on July 29, 2013, 09:50:43 PM
Can you take another pic for us?

Looking at what was said RE breadboarding, it is looking strange...

You could have a working distortion circuit that sounds great, but that doesn't mean its exactly correct./
Title: Re: Clean tone but no distortion(HELP)
Post by: bluebunny on July 30, 2013, 03:40:06 AM
Your IC has no power going to it.

It's a 741, so power comes in on pin 7.  But you're right about the resistors.  The photo looks like it's disconnected from any power supply.  That large blue (100 ohm) resistor top-right should be connected to the 9V source.  This schematic at Beavis (http://www.beavisaudio.com/schematics/DOD-250-Overdrive-Schematic.htm) might help folks...
Title: Re: Clean tone but no distortion(HELP)
Post by: Otsismi on July 30, 2013, 01:20:59 PM
Here's some more pictures(http://img.tapatalk.com/d/13/07/31/y3y3ybyv.jpg)(http://img.tapatalk.com/d/13/07/31/epaja8u9.jpg)(http://img.tapatalk.com/d/13/07/31/ase4ysus.jpg)
Title: Re: Clean tone but no distortion(HELP)
Post by: Otsismi on July 30, 2013, 01:21:23 PM
I followed the beavis schematic religously
Title: Re: Clean tone but no distortion(HELP)
Post by: mth5044 on July 30, 2013, 02:10:21 PM
It seems as though things have drastically changed since your first picture. You've added power, LED's and a few other things. It's a little hard to follow as it seems there are jumpers in strange places. What are those large orange along the power rails jumpers doing?
Title: Re: Clean tone but no distortion(HELP)
Post by: Otsismi on July 30, 2013, 07:39:30 PM
They connect the rails. I found that the rails are connected half and half
Title: Re: Clean tone but no distortion(HELP)
Post by: Otsismi on July 30, 2013, 07:40:24 PM
I had power the first time it just wasn't connected in the picture. When I switched a capacitor it started to work. I added the diodes because I like the crunch
Title: Re: Clean tone but no distortion(HELP)
Post by: mistahead on July 30, 2013, 08:16:49 PM
They connect the rails. I found that the rails are connected half and half

Half and half aye... I may need to crack out my MMeter and do some continuity checking tonight, I though my rails (where you've jumpered using long orange) were grouped in fours with no continuity between groups, but I may have done this by just testing continuity within one group, and then down at the other end of the rail entirely, without checking anything in between.

Good to hear you've got a circuit you like mate!
Title: Re: Clean tone but no distortion(HELP)
Post by: Goodrat on October 23, 2013, 07:49:12 PM
Yeah, those rails drove me crazy one time until I discovered they were split in the middle.
BTW, if you get it working and it squeals, remove the metal bottom it is mounted on.
Title: Re: Clean tone but no distortion(HELP)
Post by: deadastronaut on October 24, 2013, 05:39:27 AM
rails: should only need  a tiny jumper between groups of five.  in the middle.

experiment with different diodes too...and switch between.