Line6 FM4 - dry signal only

[gluedtogether]

My FM4 just stopped producing a wet signal. It still powers on and the leds switch on and offI do hear a slight volume drop onthe dry signal whe engaged. Tried the reset, didn't seem to help anything. I was using a line6ower supply, can't imagine that cause the problem. I do use it frequently with a midi keyboard through a sound module before going into the pedal.

Any suggestions?

Thanks

[gluedtogether]

I just plugged it back in and noticed than one or more of the diodes near the power input get hot. D11,D12 and D16. Not sure if that could some how cause the wet signal to not get enough power. Also the filter select pot did make a "blip" ( not a technical term...) whe. I rotated it around. Still no wet signal though

[Cliff Schecht]

Never had a problem with mine. These use shaft encoders so maybe when you rotated the filter knob you pushed enough to remake a connection that has broken? How do the solder joints around the shaft encoders look?

[Processaurus]

You can check the power supply as shown in Mr Huge's schematic, there is a +3.3v supply, as well as a +/-5v supply:

http://www.aronnelson.com/gallery/main.php/v/MrHuge/Line+6/DL4_ps.jpg.html?g2_imageViewsIndex=1

[gluedtogether]

I took another check on the selection pot. it is not doing anything at this point.

i will check the voltage. Hopefully its a case where one of the zener diodes isn't working correct so the proper voltage isn't getting to the pedal. thanks for the suggestion. I will get that a shot this week.

[gluedtogether]

The solder joints look good. I am relatively gentle with the pedal. Used it with keys. It must stopped working one day...

The voltages seem off, although, not 100% percent sure I am getting an accurate reading. If they are off, do I start traci g from where the powere enters the pedal until I find the bad component?

[Processaurus]

D12 getting hot is suspicious.  It is there for reverse polarity protection from putting the batteries in backwards.  No current should pass through it in normal operation. Are there batteries in there now?  Backwards?  You can try powering up the pedal without D12 (as long as the batteries are in correctly, or you're using the power supply, like most people) and see if that helps.

You might take a leg out of D11 and D12 and verify with a multimeter that they only conduct the correct way.  Beyond that, you could post your voltages from U14, U15, and U20.  Also, what power supply are you using? Verify when its connected to the circuit its voltage is correct, sometimes when something is wrong with a power supply it can read the correct voltage when it has no load, but then sags when actually powering something.

The solder joints look good.

It is very hard to visually inspect for cracked solder joints, the way to check is just to get the joints hot and add a little bit of fresh solder.  I'd resolder the encoder and the pots.  That's one tactic for repairing pedals before busting out the thinking cap, is just take 10 minutes and resolder every joint.

One final thought, there is an alternate bypass where the bypass signal goes through the DSP, that may shed some light on what is working and what isn't.  You hold down the A and C buttons when you plug it in to set it to the alternate bypass.

[gluedtogether]

I only used the correct line 6 power supply with the pedal.

I will try resoldering and see if that helps anything. If not I will post the voltages. I am not steady enoug to start desoldering the surface mount.

Thanks for the suggestions