My old Boss DM-2 just died.

[Burstbucker]

I've had this pedal for many years and it just died on me and I don't know what happened.

The pilot light comes on and off with the footswitch but there is absolutely no sound coming out even when the pedal is in bypass mode.

I doubt that it's the input or output jacks because I just cleaned them with Deoxit and that did nothing.

Any clues as to what might be the issue with this thing?

[antonis]

If your pedal is dead at both ON & Off states, you're lucky enough 'cause your issue is somewhere around footswitch wiring..
(maybe an aged joint between In or Out jack and switch - in case your PCB shares common ground with LED on switch, I shouldn't check for that part continuity..)

[Burstbucker]

Yeah I had a hunch that it might be a good thing that it doesn't pass sound in either state,  whether it's on or bypassed.

It might be a cold solder joint on one of the jacks.

There have been times in past where I mistakenly used a regulated power supply rather than the recommended Boss ACA- 120V power supply but all it did was to introduce some 60 cycle hum into the guitar signal but it never smoked anything in the pedal, last night I did use just a regular unregulated 9 volt wall wart by accident, then when I noticed that there was no sound coming out when the pedal was connected,  I swapped it out for another power supply that I used with this pedal for years without a problem and still there is no sound.

Is it possible that I damaged the pedal by powering it with a regulated 9 volt power supply?   The polarity was correct.

[Addy Bart]

I'm not 100% sure but I believe the old Boss pedals use a 12v psu or a 9v battery.

[Burstbucker]

It says on the pedal to use a Boss ACA- 120V adapter which basically puts out 12 volts and the pedal's circuit regulates that down to 9 volts.

[Burstbucker]

I also tried it with a battery last night and it still doesn't pass signal.

[antonis]

Usually, you can't damage any circuit device when powering it with much lower voltage source..
Your pedal has some kind of (AC) voltage step-down transformation ,for further rectification/regulation inside it, so your 9VAC wall-wart just couldn't provide circuit necessary working voltage..

Do your ordinary Boss ACA- 120V & 9V wall wart power supplies share exactly the same plug..??
(sometimes it's difficult to discern a 2.3mm centre pin plug from a 2.1mm one..)

Edit: Forget the above as long as you have power on LED.. 

[Burstbucker]

Good to know that I probably didn't damage the pedal with the 9 volt adapter that I used.  Just a coincidence that it didn't work when I did that I guess.

Hopefully it's just a loose jack or bad solder joint on the jack.

[antonis]

I should also pay attention on switch joints.. 

[Burstbucker]

Do you mean the wires on the footswitch?

I figured that since the LED comes on and turns off whenever the footswitch is activated that that would rule out any problems with the footswitch, no?

[antonis]

I shouldn't be so sure about that..

LED wiring definately works but that doesn't guarantee all poles/throws good switching..
Despite footswitch good operation, there is always the issue of lug/wire(PCB pad) bad joint..

[Mark Hammer]

If it was only a matter of getting clean but no delay, then one would check for a misbiased delay chip, or perhaps a fried switching FET.  If there is no sound in either effect or bypass mode, then the first thing to consider is those points where both clean and effect signals MUST pass through.  And that points to either the input or output buffer stages.

The first place to check is the emitter/output of Q1 in the input buffer.  If you can measure no AC change to signal input at that point, then nothing is reaching the remainder of the circuit.

[Rob Strand]

It could be the input or output buffer.  Probably the input buffer - as Mark said.
Check the DC voltages around Q1.

I'm sure this problem has come a a couple of times over the years.

[Burstbucker]

Man, I must apologize to you guys for wasting your time.   I started digging into this thing tonight and eventually found that the input jack is about to give up the ghost.  The part that makes contact with the tip is really soft and loose and looks like it might eventually fall off completely due to metal fatigue.

So I bent it back towards the center of the jack and it is working like a charm again, much to my relief!

I was just a bit spooked that maybe the power supply damaged something.  As you can tell, I'm no electronics tech.  I've built a bunch of simple fuzz faces, distortion pedals, treble boosters and a bit of tube amp repairs but that's about it.  If something beyond jacks would have been the problem with my DM-2 I would have broken down and taken it to a real tech but thanks for all your comments guys!

[Rob Strand]

Man, I must apologize to you guys for wasting your time. 

Not at all a waste of time.   That's life debugging electronics.
You've just got to dig around until you find it.  Which you did!

[Mark Hammer]

Fix enough things and you'll soon realize that much of the time, it's something mundane and/or dumb.

[bluebunny]

Rob and Mark are quite correct.  Pretty often it's nothing "electronic", just "mechanical".  I had a problem once that turned out to be a cracked pot track, but without bouncing around ideas and experience with the good folks here, I might never have found it.

[Burstbucker]

Thanks again for your help guys and for taking the time to respond to my post!

[antonis]

As well said above, we all wish "electronic" malfunction issues be limited to "mechanical" ones..