Slambox "SHO" and 9V Zeneer

[dc001013]

Hi guys first post here. There's still ALOT I need to learn but I'm currently building Madbeans Slambox in the the same housing as the Neutrino, "Eternity" also from Madbean, but my question is there anything I can sub for the Zeneer on the Slambox? I stocked up on my parts from smallbear but forgot the Zeneer diode. RadioShack only has like a 5.6 or something like that which I did go ahead and buy but I was going through some other layouts of the SHO and I found one verified using two 1N4148's in D1 and 2 instead of Madbeans suggested 1n4001 and 9.1 Zeneer.

Simply put...is it ok to use other Diodes here? Also, I was under the impression that 9v zeneers were used for polarity protection or overload. Again I'm a newb.

Thanks in advance.

[jasonphilly77]

Hey dc001013,

Did you ever find an answer to this? I'm in the same boat as you were. Thanks!

-jphilly77

[gjcamann]

I haven't seen the slambox circuit, but typically in the SHO, the zenier is used to protect the MOSFET. But you can probably get away without it - especially if you're not using this infront of a boost. You could put two 5V zenier's in series (or something like that) and get the same effect.

I would just skip it, use the pedal as is, and get the zenier with your next order because you could blow 20 MOSFET's before you pay for the shipping for 1 zenier. And chances are you probably will never blow the MOSFET anyways even without the zenier.

Good luck..

[Clayford]

Those diodes are there to protect the BS170 from static discharge. A pair of 4148's or a 4001 and a 9v1 should work without any problem. Zach has also done it with a single. I have a 1n4738 in mine seems to be working just fine.

[davent]

I think the first SHO's used a pair of 4148's, like mentioned above, to protect the mosfet, later versions came to use the single 9v1 zener.

http://hotbottles.files.wordpress.com/2012/03/zvex_sho.gif

[jubal81]

You could also use an LED.

[midwayfair]

no no no. The reverse conductance on an LED is like 20V! A static discharge that large on the gate will still kill the MOSFET.

9.1V Zeners are 4c each at Tayda. A BS170 costs 26c and I have 100% blown them in unprotected circuits. MUCH cheaper in the long run to just get the right part http://www.taydaelectronics.com/1n4739a-1n4739-zener-diode-9-1v-1w.html

Plus it's not like Zeners aren't useful otherwise -- they're used as crude regulators in charge pump circuits, etc.

EDIT: Get some 3.3V Zeners while you're there -- one all by itself is a highly asymmetric clipping diode.

[pickdropper]

no no no. The reverse conductance on an LED is like 20V! A static discharge that large on the gate will still kill the MOSFET.

9.1V Zeners are 4c each at Tayda. A BS170 costs 26c and I have 100% blown them in unprotected circuits. MUCH cheaper in the long run to just get the right part http://www.taydaelectronics.com/1n4739a-1n4739-zener-diode-9-1v-1w.html

Plus it's not like Zeners aren't useful otherwise -- they're used as crude regulators in charge pump circuits, etc.

EDIT: Get some 3.3V Zeners while you're there -- one all by itself is a highly asymmetric clipping diode.

Just a heads up on Zeners from Tayda.  During some Function FX stuff recently, both Brian and Forrest had trouble with a build that ended up being traced back to Tayda Zeners.  It was fixed by using ones from Mouser.

[rullywowr]

no no no. The reverse conductance on an LED is like 20V! A static discharge that large on the gate will still kill the MOSFET.

9.1V Zeners are 4c each at Tayda. A BS170 costs 26c and I have 100% blown them in unprotected circuits. MUCH cheaper in the long run to just get the right part http://www.taydaelectronics.com/1n4739a-1n4739-zener-diode-9-1v-1w.html

Plus it's not like Zeners aren't useful otherwise -- they're used as crude regulators in charge pump circuits, etc.

EDIT: Get some 3.3V Zeners while you're there -- one all by itself is a highly asymmetric clipping diode.

Just a heads up on Zeners from Tayda.  During some Function FX stuff recently, both Brian and Forrest had trouble with a build that ended up being traced back to Tayda Zeners.  It was fixed by using ones from Mouser.

That is interesting, pickdropper.  Much appreciated that you shared that as I bet this could help some others down the line troubleshooting.  I will keep it in mind for sure.

As far to the original poster...I feel that you should populate that D2 9.1v zener with those two 5.1v zeners in series until you get some 9.1v in on your next order.  If you are in the US, I can even send you a few for free just PM me.

[pickdropper]

Just for the record, the Tayda Zeners might be OK, it is just something to keep in mind if you run into trouble.  The quality of Tayda parts is somewhat variable.  I've received some out of spec stuff as well as some components that were fine.