Zener Diode repair (learning opportunity)

[LuvDemEffects]

Noticed odd behavior (cyclical popping) from an EHX Silencer Pedal, when plugged into DC Power Supply. Disassembled, removed old batter, installed new battery, reconnected guts of pedal and seemed to work off battery power. I did notice that "electronics smoke" smell upon opening the pedal, but took a chance at reconnecting the power anyhow. It seemed to function properly but did feel warm around the DC Barrel Connector. After a few minutes, I picked up the board and noticed that the Zener Diode ZZ5 had fallen off, all it says is XE with a clover shape. Three questions?

1. Does it matter if i leave this off the board? (it seemed to operate better after the component fell off the board, and i am using regulated EHX 9.5V power supply)
2. Assuming i want to fix it to original spec regardless, how do I spec this diode to buy a replacement?
3. Are there good ways to solder on surface mount boards (or any advice other than "be careful"? )

In the meantime, running off batter seems to be a non-issue, and i am assuming the diode only affects the DC from an external power supply, but if that is an incorrect assumption I am humbly ready to learn the truth!

 

[Robert]

XE looks like SMZJ3797A, a 22V zener diode.

My guess is that it's connected across the DC jack to ground. If that's the case it offers reverse polarity and overvoltage protection.

Is there any chance the pedal got plugged into the wrong power supply?

 

[LuvDemEffects]

Anything is possible, but exposing it to more than 22V very unlikely. I don't think that happened before i put it on the shelf, although it had been sitting for a bit. I am surprised that the solder popped so easily unless it got hot enough to loosen a weak solder joint or was arcing (if thats possible at 5V and a few hundred mA)?...I tried switching the power supply with other pedals in the chain and they were fine, so i don't think there is anything weird with the power supply.

Thanks for the recommended spec SMZJ3797A. Is 22V a common choice for a 9V powered pedal? (Maybe depends on what componentry it's protecting?) sounds like it did it's job, and it's probably a good idea to try and replace it if i want to use external power ...

 

[LuvDemEffects]

I pulled the datasheet for the SMZJ3797A and looks a little different (more square on the datasheet, vs more rectangular on the part removed), also varying voltages are available available. Does anybody have an idea how i can identify the specific voltage spec for this EHX Silencer Application?