EHX Small Stone Nano Gut Shot?

[david1991ross]

I recently acquired an EHX Small Stone Nano with what I think is a blown up protection diode. I was wondering if anyone has a gut shot of the pedal near the DC jack? I'm trying to determine what components are near that area and if my pedal is salvageable, although I don't have high hopes. Thanks!

[Rob Strand]

I'm not sure about the Small Stone specifically but some nano's have a small SMD diode in reverse across the DC input supply for reverse supply protection.  As soon as you have a fault it will fry.  Others have a more beefy 1N4004 through-hole diode.

This guy outlines a fix for the Bass Balls nano.   He replaces the useless SMD part with a though-hole part.   This link and some more comments came up in a recent thread started by aion regarding the EH hot tubes pedal.
https://mimmotronics.com/blog/emergency-room/er15/

If you want to persue the SMD part, I can only find this barely good enough image,

http://jablog.ru/uploads/images/00/02/87/2012/08/27/871ad3.jpg

The best I can do is see the marking JG, and maybe designator D3.

Which you can see is a BAV99 diode.   Not an uncommon part.
https://smd.yooneed.one/code4a47.html

Unfortunately I don't have a lot of confidence in reading the JG marking.

A good place to start is to see if you can read your part in the right light.  Perhaps carefully wiping the top.
Next trace the connections to the part.  See if it does go to the supply.  Then maybe see if the PCB tracks go to the expected pins on the diode based on the BAV99 datasheet.

[Mark Hammer]

Not entirely clear that's just one component.  The likelihood it is a protection diode is pretty good since its immolation is precisely what they are intended to do: sacrifice themselves for the sake of the rest of the circuit.  But is what we see only ONE component.  Even enlarged, I can't tell.

[ElectricDruid]

Ooofff! That one's had a *hard* life, hasn't it?!? 

I don't think that means it's necessarily beyond fixing though. Good luck!

[Rob Strand]

The diode is mounted right behind the DC jack (no other parts).   It's almost certainly a reverse protection diode.


Actually, from the good diode on the OP's original pic and the pic on the Russian site we can see the PCB has the diode part number:   MMBD4148SE

There's a number of MMBD4148 variants and the MMBD4148SE is a dual diode.  Perhaps only one diode is used.   The other thing is the marking (on the part) for MMBD4148SE is suppose to be D4.    So did I read the JG marking wrong on the Russian pic or did EHX substitute the diode?

The easy way to find out is to simply read what is on the other good diode on the PCB!