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Boss ME - 25 Help. No signal?


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I apologize if this is the wrong place, im scouring the web for help. My ME-25 is not receiving an input signal. I know it isn't the output because I can hear the effects running and the white noise from the unit when I crank it. The unit powers on but it acts as if my guitar is turned all the way down (which it isnt). I've tried different cables, guitars, batteries, power supplies, turning off the noise gate, factory resets, etc. Any idea what's happening?

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The only other thing I can think of is your effects levels are off. The unit should pass a clean signal regardless. Anyway to do that? Is there a killswitch?

 

Try the Electric Guitar forum. Or wait for WRGKMC or the rest of the tech minded guys here.

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A multi-effect unit? These are not DIY-friendly at all to troubleshoot or fix. Most of them are all digital: signal goes in, converted to ones'n'zeroes, then [computer] DIGITAL MAGIC HAPPENS [/computer] then the new ones 'n' zeros are converted back to an analog sound wave and sent to the output jack. You'd need a signal generator and audio probe to try and physically find where signal stops, but once the signal is converted to digital, the audio probe won't help.

 

If it's under warranty, send it back. If it's not under warranty, contact Boss about getting it repaired.

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The only things you can check are of course your guitar cord. Make sure you've tried others.

 

The second most likely suspect is the input jack itself. From the pic on their site it looks like they use PC board mounted 1/4" jacks.

Theses kinds of jacks aren't very durable. One good yank on a cord can damage the jack internally or crack a solder joint that connects it to the board.

 

First thing I'd do is open it up and take a careful look at the input jack solder connections. Wiggle the jack and see if you see the connections move. If they move re-solder them and you should be good to go.

 

The other possibility is these PC mount jacks are often those plastic type. If you do have a solder joint problem, be sure to solder quickly and avoid over heating the jack. The contacts inside the jack are weak designs too. They weld them in place using melted plastic and the actual contacts are cheap metal that tend to flatten out and make a poor contact. I've been able to go into the jack with a spring hook and flash light to bend the contacts to produce more pressure but for most simply replacing the jack is the best solution. They aren't that hard to replace. You do need a solder sucker to remove the excess solder. They usually glob it on heavily when wave soldering the boards.

 

There are a couple of different type replacements but they aren't too hard to find. Its likely a switched jack that also provides a DC voltage connection so its a 3 contact normally open jack (stereo type) When the jack is inserted, the sleeve provides a DC voltage connection to ground and activates the unit. Sometimes they put an identifier number on the jack so you can google up a replacement. Otherwise post a pic and I should be able to identify it for you.

 

If its not the jack then you have to signal trace the circuit and see where the signal goes and stops. If it feeds into a transistor or chime and you have nothing coming out of it then that's likely where your failure winds up being.

 

Oh, is you have to unscrew any boards, be sure you lay your screws out in order so when you reverse the process and put it back in, you have the right screws for the right holes. Many times you have different length and different types of screws. You don't want to damage the plastic housing jamming the wrong sides screws in the holes. Mark the places you take the screws out with a magic marker too. Makes it easier to find them when reassembling.

 

You should have no bush parts left over. (Bush parts are parts techs forget to put back when reassembling and thrown them in the bushes when they leave a customer) Corny joke but oh so true when you work with other technicians all day long.

Edited by WRGKMC
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