SOLVED Lamb Chop just died.... Help

[Anthonyj]

After about a year and half of good use my Lamb Chop just stopped working today.... I did some trouble shooting with an audio probe and the issue seems to be at C1 right in the begging. I have audio on the left side of the cap but not the right (based on picture below), if I bridge the connection everything works but it pops when turned off and on and I feel like it doesn't sound right. I replaced the Cap already with a new one, but the problem persists.

The pedal was built for 18V and is running with the charge pump.
Any help would be appreciated.

 

[Nostradoomus]

post pictures

 

[Anthonyj]

Sorry for the bad pictures.

 

[darwin999]

Hmm, how's that Q1 FET right behind it, the 2N7000?
FETs are very static sensitive, they can easily be destroyed.
You might check the DC voltages on the 3 legs with a good multimeter.

 

[Nostradoomus]

if it was fine for a year and a half I'd suspect mechanical wear on something unless it was plugged into an improper supply. Jacks/switches etc, test the continuity

 

[Anthonyj]

So for voltages left to right according to the picture.
Leg 1 15.72v
Leg 2 7.52v
Leg 3 15.74v

The continuity around the area seems good other than jumping that capacitor,

 

[JohnnyCreepy]

Leak or dirt on the electrolyte cap circled?

 

[Anthonyj]

I couldn't really tell so I replaced it any way but that didn't change much. not sure if this helps but if I bridge the cap and the pedal gets a signal its fades away slowly when i break the bridge.

 

[JohnnyCreepy]

I couldn't really tell so I replaced it any way but that didn't change much. not sure if this helps but if I bridge the cap and the pedal gets a signal its fades away slowly when i break the bridge.

More good or bad guesses! Is D10 orientation right as it’s hard tell it looking your pic? If you jump the relay bypass board, do you get signal?

 

[Anthonyj]

D10 is in the correct orientation, and that extra board on the bottom is the charge pump board knocking it up to 18V so it's still true bypass so that signal it good. The issue is just the effect.

 

[Sturdag Lagernathy]

So for voltages left to right according to the picture.
Leg 1 15.72v
Leg 2 7.52v
Leg 3 15.74v

That's not right.. did you try a new mosfet?

 

[Anthonyj]

That's not right.. did you try a new mosfet?

Looking through my bag I only have some Jfets I don't have a replacement for the 2n7000. Is it possible I killed it using the charge pump pcb?

 

[Anthonyj]

I replaced the 2n7000 with a new one and also removed the power pump since I am using a passive bass and maybe don't need the extra head room.

Could the 18v have killed the 2n7000?

 

[Feral Feline]

Headroom is good, removing the Charge-Pump is like cutting off your nose 'cause you've got Gout and your toe hurts.

The 18V won't have killed the 2N7000, not according to this DataSheet:

https://ww1.microchip.com/downloads/en/devicedoc/2n7000-n-channel-enhancement-mode-vertical-dmos-fet-data-sheet-20005695a.pdf

Drain-to-Source Voltage .......................................................................................................................................BVDSS ​

Drain-to-Gate Voltage ...........................................................................................................................................BVDGS ​

Gate-to-Source Voltage........................................................................................................................................... ±30V​

At the bottom of the PDF you'll see that BVdss and BVdgs are rated at 60v — so I'd say 18V is well within the operational parameters.

As has been noted in the thread already, MOSFETs are very susceptible to ESD — some how some way a charge built up and was released, maybe? — the discharge possibly caused by mechanical wear & tear (also mentioned earlier in the thread) or if the pedal was dropped that could crack a solder-joint or...

Yeah, I'm grasping at straws here, but possibly the one that broke the camel's back?

 

[Anthonyj]

Not sure what killed the 2N7000 but it is working since being replaced, ESD sounds like a possible culprit being in the carpeted basement during the winter. I'm going to try it again with the charge pump later since it's only 4 solder joints to use.

Thaks for all the help.