MXR Doubleshot Distortion M-151 not working

[DS-1]

Hi guys!

I've bought used this pedal, that using a 9v adapter (yes, I know it works with 18v adapter, but online I've found several users that use it with 9v without issues).

With the effect OFF, It works with the clean sound. When I turn it on, there's no sound.

It turns on and FOCUS yellow leds even with buttons not pressed and it doesn't sound when the effect is ON.

I've opened it and maybe I've found a burned resistor. It's the R81, near the DC jack.

Can anyone please measures it?

Thanks a lot in advance!

[Plexi]

Post some photos!

[GibsonGM]

...and, can you find a schematic to post??   

Welcome to the forum, Giuseppe...

[anotherjim]

I can't find the scheme. Can't find anything similar from MXR either.
Probably R18 is a current limit protection resistor on the DC input, but I can't find an MXR scheme that employs one. If it is doing that job, probably temporarily replacing it with a 100R may serve to get it going. You could trace its relationship to the power wiring (and any polarity protection diode) to improve the chance of that being all that it does.

[DS-1]

...and, can you find a schematic to post??   

Welcome to the forum, Giuseppe...

Hi guys!I can't find any schematic for it and there are all SMD components in there...

Tomorrow I'll post a couple of pics of the PCB!

[DS-1]

I can't find the scheme. Can't find anything similar from MXR either.
Probably R18 is a current limit protection resistor on the DC input, but I can't find an MXR scheme that employs one. If it is doing that job, probably temporarily replacing it with a 100R may serve to get it going. You could trace its relationship to the power wiring (and any polarity protection diode) to improve the chance of that being all that it does.

Amazing find!

Tomorrow I'll try it ;-)

[DS-1]

Here we are now!

Here's the pics of the inside of the MXR

https://drive.google.com/open?id=1ctf9uB2ZDx3xHj1Ez8xdN4Anw_JZSz_2

Unfortunately I've broken a pot, it is hard to extract the pcb from the inside 

https://drive.google.com/open?id=1KF5aSgpc43HaahMobOfn5LorgkPQm37n

https://drive.google.com/open?id=1wdr9CkRcyh7V1TnJOv6Sso_9P-3K2JR-

R18 on this PCB is 11k.

I have to say that the pedal is 18v. I've never tried it with 18v, but I've a friend of mine that uses it with 9v without problems.

[Delicieuxz]

Your pictures aren't there. Did you remove them?

If you burnt a resistor near the power jack, did you maybe use a too-high value AC adapter? A lot of units use 24v adapters but, like you mentioned, the Doubleshot uses an 18v adapter. I guess it might be easy to mistake a 24v adapter for an 18v one.

Using a 9v adapter shouldn't hurt it, though.

[thermionix]

I think it was dead when he got it.  That's how I read it anyway.  Could be yet another reverse power victim.

[Delicieuxz]

I think it was dead when he got it.  That's how I read it anyway.  Could be yet another reverse power victim.

Does that mean that using a 9v adapter or any under-rated adapter actually can harm a pedal?

[thermionix]

If the polarity is reversed, yes.

[matlevo12]

Hi.
If that ever helps someone : I got a malfunctionning M151 ,symptoms being very low volume, glitchy and the two focus lights stayed on all the time, even when the buttons are not pressed).
The culprits were R81 et R39, both 10R (code 100), both dead. I just replaced them and everything's back to normal.