Help: ODB-3 goes silent after a while

[shtrom]

Hi guys,

I have an odd problem with a Boss ODB-3 I got second-hand from eBay. I don't seem to be able to solve it on my own, so I thought I'll take it to you. I'm new here, so please excuse any oversight. Anyway, here is my problem.

When the effect is on, the output signal gradually “fades out,” until it's completely silent, it then stays like that until I give it a couple of days' rest. In this state, turning the effect off still lets the normal dry signal through. Also, the battery's new.

Now, my electronics classes are far behind me, but it looks like some capacitor wreaking havoc. However, I am not able to diagnose the problem further. I've opened the pedal, and the circuit board is clean, with no apparently fried component or bulgy capacitor.

Any idea what the problem could be, or what I should pay more attention to to understand the cause, and hopefully fix it

I'm ready to attack it with a soldering iron and replace parts, I just don't know what to replace...

[cybersnyder]

Be thankful. ;-)

Sounds like a dying battery or a bad power supply. The symptoms also sound like a bad capacitor, but the length of time that it's working and then fading makes that unlikely given the size of the capacitors.

[Testing_123]

the output signal gradually “fades out,” until it's completely silent

How long does this take -- are you talking seconds, minutes, or hours for that fade out to occur?

When first engaging the pedal, does the initial tone sound as it should (appropriate tone characteristics that vary with the gain/drive setting, correct output volume), etc...

If this behavior occurs, then you let is sit for a few days and try it again, has the battery been discharged, or is still fresh? Use a multimeter to check the battery voltage -- new batteries should measure 8.9-9.2 v, while I've seen some Boss pedals stop working correct when the battery has only dropped down to low-to-mid 8's v.

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Might be worth building an audio probe (just a couple of parts -- see here) and tracing the circuit signal path to isolate where things start to go wrong.

[shtrom]

Originally Posted by Testing_123

How long does this take -- are you talking seconds, minutes, or hours for that fade out to occur?

It's usually minutes.

Originally Posted by Testing_123

When first engaging the pedal, does the initial tone sound as it should (appropriate tone characteristics that vary with the gain/drive setting, correct output volume), etc...

Most of the time, it did, but I just tried again, and it seems to have worsened. When the pedal is not engaged, everything's fine, and I have a clean dry sound. When I engage it, even with the balance all on the dry side (no OD), the sound still comes out with a lot of fuzz, and it stutters (only about every second note get through).

While I was at it, I had a closer look at the board, and it doesn't look as clean as I thought.

The solder points around the power connector have a nasty-looking brown colour. Does it look normal to you?

Originally Posted by Testing_123

If this behavior occurs, then you let is sit for a few days and try it again, has the battery been discharged, or is still fresh? Use a multimeter to check the battery voltage -- new batteries should measure 8.9-9.2 v, while I've seen some Boss pedals stop working correct when the battery has only dropped down to low-to-mid 8's v.

The battery sitting in there was down to 8.6V. I replaced it with one at 8.9V, but it didn't change the overall behaviour.

Originally Posted by Testing_123

Might be worth building an audio probe (just a couple of parts -- see here) and tracing the circuit signal path to isolate where things start to go wrong.

Thanks for this pointer. I'll give it a go!

[Rob22315]

Originally Posted by shtrom

The solder points around the power connector have a nasty-looking brown colour. Does it look normal to you?

That's left over rosin from solder. It looks like someone in Boss QA touched up the board after it went through the wave solder machine. A little acetone, aka fingernail polish remover or intake cleaner, will take that off. It won't affect performance but it will make it hard to see if you have a solder short between pads. Notice how the solder joints in the brown areas looks different from the solder joints elsewhere? The ones in the brown area were done by hand.

How do I know? I did solder QA during a summer job.

I hate to say this but it sounds to me like one of the solid state components is failing. Can you see any burnt parts on the other side of the board? Is there a burning electronics smell coming from anywhere on the board.

[Testing_123]

It looks like someone in Boss QA touched up the board after it went through the wave solder machine.

That, or the pedal's previous owner attempted to do a little modification or troubleshooting him/herself?

Can you also post a component-side picture of the board?

[Beersurgeon]

Originally Posted by Testing_123

That, or the pedal's previous owner attempted to do a little modification or troubleshooting him/herself?

+1

I work for an electronic company out of high school for a while soldering and these joints look awful!!! I can promise you that this isn't the work of a QA at Boss. Way too sloppy!!

I would first clean up the board like Rob22315 suggest and see if any of the joints are connect by misc solder. If a capacitor has two currents going into it instead of the one current it's suppose to regulate, this would easily cause it to over heat and quit working. From the pic you supplied, there looks like there could be several joints that are connected that aren't suppose to be.

[Rob22315]

Originally Posted by Beersurgeon

I work for an electronic company out of high school for a while soldering and these joints look awful!!! I can promise you that this isn't the work of a QA at Boss. Way too sloppy!!

Unless it happened to be a summer intern doing the work!!

You're probably right, a PO tried to do some mods and messed it up. To the OP, inspect the solder joints where the brown spots are, then check the components on the other side of the brown spots. Maybe a bad parts substitution or install.

[shtrom]

Originally Posted by Testing_123

Can you also post a component-side picture of the board?

As far as I can tell, everything looks good here. No apparently burnt component nor funny smell.

Originally Posted by Beersurgeon

I would first clean up the board like Rob22315 suggest and see if any of the joints are connect by misc solder. If a capacitor has two currents going into it instead of the one current it's suppose to regulate, this would easily cause it to over heat and quit working. From the pic you supplied, there looks like there could be several joints that are connected that aren't suppose to be.

I went over those connections with a circuit tester, and there doesn't appear to be any unwanted connection...

Looking closer at the back of the board, there also is another seemingly burnt line, with something which looks like it could be a short.




After testing A and B, the two lines are not actually connected. However, A and C (apparently supposed to connect D4 to C30) do not seem to be connected either, which I find rather surprising... I think I'll try to patch that, see if it helps...

[Beersurgeon]

I'm about out of ideas of possible problems. I see the short your talking about and think you're probably right. I'll keep checking this thread and see if you're able to figure out the problem. Good Luck!!!

[Rob22315]

Looks like you might have found the culprit. Just make sure that B isn't shorted to C or A. I'd take a little solder braid to B to remove the excess solder from between those runs then put a jumper wire in from A to C to remake the connection.

[shtrom]

Originally Posted by Rob22315

Looks like you might have found the culprit. Just make sure that B isn't shorted to C or A. I'd take a little solder braid to B to remove the excess solder from between those runs then put a jumper wire in from A to C to remake the connection.

Well, it was the culprit for the pedal not working at all.



It's not the cleanest fix I did, but it does the work. I haven't had time yet to see whether it fix the “time-delayed” dying of the effect, but I suspect it should. I guess there has been a short, or close to, there initially, which put too much power over the line, and gradually cut it, if that makes sense. Do you reckon a short electric arc could have happened there?

Anyway, that heatshrink tube should fix the isolation issue. I'll tell you guys about the final conclusion as soon as I get to test the pedal thoroughly (i.e. this weekend).

Thanks a lot for your help so far!

[Beersurgeon]

I'm glad you found the problem!!!!

[Rob22315]

Congrats!! As long as you didn't lift a pad, that repair should last. It's inside the box so who cares if it's ugly as long as it's permanent.

[Testing_123]

Cool -- always good to hear a successful troubleshooting experience.

[shtrom]

Yep, after more thorough attempts, the pedal now holds the distance. Thanks a lot for your help, guys!

[Beersurgeon]

I'm glad everything works well after a month or so!!!!