Misadventures with the OD-3

Endless Mike

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This would be the same OD-3 I posted a thread about last week or so (it's all a blur lately...)

So I opened it up, and found that it had been modded. Now I *always* do the nip and tuck mod found elsewhere on TDPRI to all my OD-3's. That involves reducing C14 and C35, C33 with R51, replacing D10 and D11 with 1N400x and that's it. But what's been changed in this pedal is C12, C14, C15, C22, C24, C33, C35, R39 and R51.

I understand C14, C35, and C33 with R51. The rest of these are a mod that I also found here on TDPRI, but indirectly by doing an internet search which led back here to the Stompbox subforum. R39 is not something I found here or anywhere else, and I searched extensively using a number of different terms. I have no idea what R39 is about.

I've returned *everything* to stock values with exception of C14, C35, C33 and R51, as I know those. As ana side, D10 and D11 have been replaced with the 1N400x, so I've not touched those.

Finally, here's the issue - with everything back to stock, except the 'nip and tuck' mod of C14, C35, C33 and R51, D10 and D11 something is not right. I've used an OD-3 modded for those six parts since approximately 2010 or so. There's always more than enough gain on tap. I've never needed or wanted to turn the gain pot up past about 1 O'Clock. With this one, I have the gain maxed out and it's still not quite enough. Yes, I understand that C33 and R51 will reduce gain. That's the whole idea! but even with the gain reduced via those changes, as I said, there's always been enough. But in this case, not only is it not enough, it doesn't sound or feel the same as all previous 'nip and tuck' modded OD-3's, at the one O'clock setting or even with the gain on full.

Cousin Paul asked for pictures, so I've included those. I'd greatly appreciate any insight, input or assistance sorting this out. Admittedly I've been pretty out of it lately due to some pretty serious family circumstances, lack of sleep and so on. But I was very careful returning all but those six parts to stock values, although I wish I'd had the presence of mind to write down the values of the parts I removed, especially R39, as that one is a real mystery.

Thank you all!

OD-3 1.jpg
OD-3 2.jpg
OD-3 3.jpg
 

11 Gauge

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R39 is not something I found here or anywhere else, and I searched extensively using a number of different terms. I have no idea what R39 is about.
R39 forms a highpass filter with C23. Given its fairly large value it would have to be reduced significantly to raise the corner freq to a point where it would have a notable effect.

I can only guess that maybe someone reduced the value of R39 in the hopes of increasing gain.

...Unless they increased the value of R39. I have no idea why anyone would do that.

Personally IMO, there's no use in dinking around with R39, so I'd return it to its stock value of 100K.
 

11 Gauge

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Finally, here's the issue - with everything back to stock, except the 'nip and tuck' mod of C14, C35, C33 and R51, D10 and D11 something is not right. I've used an OD-3 modded for those six parts since approximately 2010 or so. There's always more than enough gain on tap. I've never needed or wanted to turn the gain pot up past about 1 O'Clock. With this one, I have the gain maxed out and it's still not quite enough. Yes, I understand that C33 and R51 will reduce gain. That's the whole idea! but even with the gain reduced via those changes, as I said, there's always been enough. But in this case, not only is it not enough, it doesn't sound or feel the same as all previous 'nip and tuck' modded OD-3's, at the one O'clock setting or even with the gain on full.
Forgive me, but I can't really make out what you've put in place for R51. It looks like either 2.2K or 1.2K, but I can't tell. But either way, that still seems like a sizeable increase.

...But if you feel confident that it's not the issue here, it's really most likely got to be an issue of a change in resistance for a component. I'd say to double check that there hasn't been another resistor changed with one that looks like the stock 1/8-watt stuff.

The only other thing I could think of is maybe to check that someone hasn't changed the drive pot to something lower than stock, like maybe subbing a 50K pot for the stock 100K one.
 

Chipss36

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If I was trouble shooting, I would look at the opposite side of the pcb first, a close and critical inspection of all solder joints, any Stray solder, a lifted trace, things like that….
 

cousinpaul

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The two 1N4OOX at the bottom of the board (D6 and D7) look like they're oriented wrong. They look like they are both facing the same direction. If so, try turning one around. D11 and D12 could have the same problem. There should be arrows printed under the diodes indicating the right orientation. All diode pairs oppose each other on the schematic.

Those boxed caps look hinky to me as well. Not something I'd expect to find in a Boss pedal.
 

11 Gauge

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The two 1N4OOX at the bottom of the board (D6 and D7) look like they're oriented wrong. They look like they are both facing the same direction. If so, try turning one around. D11 and D12 could have the same problem. There should be arrows printed under the diodes indicating the right orientation. All diode pairs oppose each other on the schematic.
The orientations are actually okay as is, in the same way that D4/D5/D6 in the SD-1 are all facing the same direction on the PCB.
 

Endless Mike

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Forgive me, but I can't really make out what you've put in place for R51. It looks like either 2.2K or 1.2K, but I can't tell. But either way, that still seems like a sizeable increase.

...But if you feel confident that it's not the issue here, it's really most likely got to be an issue of a change in resistance for a component. I'd say to double check that there hasn't been another resistor changed with one that looks like the stock 1/8-watt stuff.

The only other thing I could think of is maybe to check that someone hasn't changed the drive pot to something lower than stock, like maybe subbing a 50K pot for the stock 100K one.
You are correct with the first one. You had described changing R51 to 2.2k along with C33. As you wrote at the time "...but it would require decreasing C33. The good news is that it is a high pass filter that is exactly the same as a TS, so using the popular values for the TS gain mods would work perfectly there." You went on to specify the values, but you said you didn't want this out in the world at large. Although it *can* be found on TDPRI, as you said that, I'm inclined to respect that, still after all these years.

I'll check all of those. I greatly appreciate your help, along with Cousin Paul, and everyone else. I'll take a look later today when I actually get some time for myself, which is rare and hard won these days.
R39 forms a highpass filter with C23. Given its fairly large value it would have to be reduced significantly to raise the corner freq to a point where it would have a notable effect.

I can only guess that maybe someone reduced the value of R39 in the hopes of increasing gain.

...Unless they increased the value of R39. I have no idea why anyone would do that.

Personally IMO, there's no use in dinking around with R39, so I'd return it to its stock value of 100K.
I don't believe I made that change. The only changes I made were those you and I discussed several years back. I returned R39 to stock. I wouldn't *ever* want to increase gain, although this current situation is an exception. I'd just like to get it back to the point it would be at if I made the six changes you described in your 'nip and tuck' mod. I have some other changes saved in a document that you had offered in private conversation, but I have never chosen to make use of them as the six component mod is absolutely *spot on* perfect and it's all I've ever used since you first posted that mod here years back.

Oh, and I did return it to the stock value.
 
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Endless Mike

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The two 1N4OOX at the bottom of the board (D6 and D7) look like they're oriented wrong. They look like they are both facing the same direction. If so, try turning one around. D11 and D12 could have the same problem. There should be arrows printed under the diodes indicating the right orientation. All diode pairs oppose each other on the schematic.

Those boxed caps look hinky to me as well. Not something I'd expect to find in a Boss pedal.
Even though I have nothing close to the knowledge and experience you and Keith do, I'd really hope I wouldn't do something that boneheaded. After all these years of modding and building pedals, I can still make some pretty idiot moves. Especially these days when there's not as much sleep as is needed, and there's some pretty crazy stuff going on at home.

The box caps are part of the 'nip and tuck' mod Keith posted here back in 2010, maybe 2013. At the time that was the only caps I had for that value. I need to go back and replace them with something more appropriately sized. That much *I* did do. The R39 and other changes, I am mystified by. The only mod I *ever* perform on my OD-3s is the six component mod developed by Keith. It's so d*mn perfect, why do anything else. I mean, it really is just so spot on in terms of the resulting change in sound created by the pedal. It's been one of my two or three favorite ODs for many years now. That's why I always keep a spare, but we see how that turned out!
 

Endless Mike

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If I was trouble shooting, I would look at the opposite side of the pcb first, a close and critical inspection of all solder joints, any Stray solder, a lifted trace, things like that….
I did. It's a bit messy. In performing Keith's mod, I've had to jumper things using the legs of the components to whatever they are connected to by traces. I thought of that, but decided it would probably only create more confusion.
 

cousinpaul

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Keith said you got the diodes oriented right. I'm wondering if there might be a previously modded component you missed on your de-mod. It might be worthwhile looking at some of the other poular mods looking for other parts that have been swapped out. I found Keeley and Wampler mods online. FSB might also be a good resource.
 

Endless Mike

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Keith said you got the diodes oriented right. I'm wondering if there might be a previously modded component you missed on your de-mod. It might be worthwhile looking at some of the other poular mods looking for other parts that have been swapped out. I found Keeley and Wampler mods online. FSB might also be a good resource.
Thanks for the reply. Sorry for the delayed response. Things are more than a bit crazy in our home right now.

As to your thoughts. I had the same. I've looked again and again and I've not seen any signs of this. Maybe this is a poor way to do this, but it seems there are always to giveaways. One, is the obvious 'that's not a Boss' component, or you have a 1/4 watt resistor where the stock parts are 1/8, as is the case here. Two, you can see the where the soldering has been done. I can't think of a time when someone has made changes, and even with the best soldering, it still looks different that what comes from the factory (do they use wave soldering?). Am I over looking something? I'll look yet again, using a very good light source. I'm going to return everything to stock, and see how it sounds. If that sounds right, then I'll try the 'nit and tuck' changes again. I'm thinking this time, leave R51 and C33 alone, just changing out C14 and C35, D10 and D11 just to reduce the bass and get rid of the nasty decay.
 

cousinpaul

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I saw a Wampler mod where the .033uf tone cap is bumped up to .1uf, kinda like the Keeley Phat mod. Might be one to check out. The Allums mod was also popular but I have no idea how it goes.
 

Endless Mike

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I saw a Wampler mod where the .033uf tone cap is bumped up to .1uf, kinda like the Keeley Phat mod. Might be one to check out. The Allums mod was also popular but I have no idea how it goes.
I'll look. I've spent the last week or two looking at all the commonly available mods, and they are legion. This could go on indefinitely. I can say that all of the solder pads that haven't been modded, with an obvious component replaced, all look pristine, as they do from the factory.
 




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