Broken boss ODB3

gregmon79 · #1 03-30-2013, 06:57 PM

So I found an old boss OBD3 in storage today. It's probably about 15 years old. Anyway, I go to plug it in and play it and it doesn't work properly. I can hear some noise coming out of my cab when it's engaged, which is the pedals distorted sounds but it's I'd barely audible. When disengaged, I get absolutely nothing. Is there something I could do to this pedal to see if I could fix it myself. I'm confident I could solder something if need be but I wouldn't know where to begin. I tried taking the board out of the bottom but it was in there pretty good so I only got it partly out and put it back in and figured I'd run it by my good friends on TB to see if you guys had any recommendations.

DannDubblewe · #2 03-30-2013, 07:19 PM

Pull the knobs off and remove the nuts and washers. The board and pots should lift out fine to see if there are any broken connections to the jacks which seems like it COULD be the case.

gregmon79 · #3 03-30-2013, 07:25 PM

Do the knobs just pop off if pulled hard enough with my fingers? And if there is a bad connection how can I tell? Will be as simple as seeing a wire loose from something?

DannDubblewe · #4 03-30-2013, 07:42 PM

Yes - the knobs should pull RIGHT off with a little effort. There's no set screw. If you have problems use a small wrench and lightly grip them and they'll come off but it shouldn't be necessary at all.

If it IS a wire then yes - it could be entirely disconnected or frayed. I'd look at the jacks as they'd be the most susceptible to that. Are the jacks's nuts tight? If you can't see anything with your eyes then it could be a deeper problem. Look for dark spots that look burnt on the solder side of the PCB or blown components on the topside. Sometimes nothing will be apparent, however you definitely should take a good look first!

Ibanezsr500 · #5 03-30-2013, 07:48 PM

If they don't have a set screw, then yes, the knobs will pull of with your fingers.

EDIT: Dan beat me to it.

gregmon79 · #6 03-30-2013, 10:06 PM

gregmon79 · #7 03-30-2013, 10:09 PM

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I have no idea if y'all can make anything out of this but it looks to me like everything is connected. No scorches. No wires not connected. One of the quarter inch plug in sides only has one wire going to it but I don't see any other wires dangling that could possible go anywhere.

Ibanezsr500 · #8 03-30-2013, 10:56 PM

Everything looks OK from what I can see in the photos.

From what you said in your first post, it sounds like the FET bypass might have issues. IMO.

At this point I usually get the schematic and my audio probe to start poking around.

Schem: http://ib1.keep4u.ru/b/2009/06/08/ab...476b4136df.jpg

How to build an Audio probe: http://www.diystompboxes.com/pedals/debug.html

EDIT: It's odd that they rely on the enclosure for the jack grounding... I wonder why they did that?

gregmon79 · #9 03-30-2013, 11:29 PM

Quote:

Originally Posted by Ibanezsr500

Everything looks OK from what I can see in the photos.

From what you said in your first post, it sounds like the FET bypass might have issues. IMO.

At this point I usually get the schematic and my audio probe to start poking around.

Schem: http://ib1.keep4u.ru/b/2009/06/08/ab...476b4136df.jpg

How to build an Audio probe: http://www.diystompboxes.com/pedals/debug.html

EDIT: It's odd that they rely on the enclosure for the jack grounding... I wonder why they did that?

Wow. Thank you much for the schem! I'm looking at it right now and it looks a little confusing. Like "the ground", which one is that? And how am I supposed to know what's what? Which one is the FET bypass? I put it back together and it still doing the same thing, no noise out of amp when off, only audible if its completely quiet. In other words, I can hear me playing the strings louder than what's coming out of the cab. I'm going to take back apart and see if I can make sense of the quick guide you linked to.

cheapbasslovin · #10 03-31-2013, 01:39 PM

Please forgive me if you did this, but did you use a new battery or verified power supply?

It's all about the basics.

gregmon79 · #11 03-31-2013, 02:03 PM

Quote:

Originally Posted by cheapbasslovin

Please forgive me if you did this, but did you use a new battery or verified power supply?

It's all about the basics.

I only tried it with a power supply. I'll try a battery and see if ghat does it. But, I do remember using this pedal years back and stopped using because of the way it is now.

gregmon79 · #12 03-31-2013, 02:04 PM

Btw, it's not a "boss" 9 volt power supply. It's an SKB pedal board powered supply built in to the board.

DannDubblewe · #13 03-31-2013, 02:18 PM

I'd look inside the jacks to ensure nothing was bent!

gregmon79 · #14 03-31-2013, 04:07 PM

Not sure if you can see, but this lil guy is just there and that doesn't like right to me. It says ZZZ at the base:

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Hellbastard · #15 03-31-2013, 04:25 PM

It looks like you got it! I opened my Monte Allums modified ODB-3 and in that position there's a 1uf 50V electrolytic cap; from the looks of your pic it is damaged. replace it an try again.

gregmon79 · #16 03-31-2013, 04:29 PM

And there's only one white white going to the other quarter inch plug in. Is that the only one that needs to be on there?

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Hellbastard · #17 03-31-2013, 04:35 PM

Quote:

Originally Posted by gregmon79

And there's only one white white going to the other quarter inch plug in. Is that the only one that needs to be on there?

Attachment 328484

That's normal. The other part of the signal is the (-) negative side and it comes through the case connection to the jack.

gregmon79 · #18 03-31-2013, 04:53 PM

Quote:

Originally Posted by Hellbastard

It looks like you got it! I opened my Monte Allums modified ODB-3 and in that position there's a 1uf 50V electrolytic cap; from the looks of your pic it is damaged. replace it an try again.

I'm sorry, no disrespect, but in English please. What is the 1uf 50V electolytic cap and what does it look like???

gregmon79 · #19 03-31-2013, 04:55 PM

And how can you tell it's damaged? I'm sorry, I just have no idea what I'm lookin at. I thought I'd see something loose or burnt you know.

DannDubblewe · #20 03-31-2013, 05:05 PM

One leg of the electrolytic has been lifted/ broken. That free floating piece should be connected to that big round thing next to it, which is an electrolytic capacitor.

A quick ebay search for "1uf electrolytic 50v" brought up THIS which is a US seller - although it's rather expensive relatively speaking, I don't think you want a quantity of 100. The picture is blurry, but it's the one you want and that particular part on your circuit board would be the reason your pedal isn't functioning 100%. How it was lifted and broken like that is beyond me, but yep! Replace it and see if it works! Just keep tabs on which side is negative and which is positive so you solder it in correctly.