Hello everyone I have some problme on my EA tremolo build. It works perfectly at the first time. However it suddenly produce a very weak sound after i disconnect the power. I switch the new BS170 and it work again. However it just die again after few connection of the power. Anyone can suggest a possible reason to this?

There are different versions of the EA Trem.  The ROG version is slightly different than both the GGG version or the original.  And I think there are a few other variations out there too.  Are you having problems with the ROG/homewrecker version?

Quote from: Mark Hammer on April 15, 2015, 11:30:56 AM
There are different versions of the EA Trem.  The ROG version is slightly different than both the GGG version or the original.  And I think there are a few other variations out there too.  Are you having problems with the ROG/homewrecker version?

Thanks , I am using the schematic:

Don't ask why but if you connect power via a stereo jack, stop it right now...

(I've build exactly the same tremolo and after some dead mosfets I changed the stereo jack to a mono one and we are happy ever after..)

Can't you just add a zener to protect it if they need the power/jack for battery savings?

Most mosfet circuits have a 9v zener from source to gate to protect them, that schem doesn't have one and may be the cause of the problem.

Edit - beaten to it!

I thought that BS170 has an internal zener protection...

Quote from: nocentelli on April 15, 2015, 02:06:22 PM
Most mosfet circuits have a 9v zener from source to gate to protect them, that schem doesn't have one and may be the cause of the problem.

Edit - beaten to it!

How to connect the zener? It is just like the way connecting the 1n4148 in this diagram? If so can I use a 1n4148?

That's the way but you have to use 9V1 zener for mosfet protection from signal greater than 9V or negative...

( although I insist that BS170 DOES have internal zener protection and capacitors and resistors at the input already attenuate most of the stadic discharge from the input jack - which is the main source of static charges in a enclosed circuit with proper shielding )

Quote from: antonis on April 16, 2015, 07:25:06 AM
That's the way but you have to use 9V1 zener for mosfet protection from signal greater than 9V or negative...

( although I insist that BS170 DOES have internal zener protection and capacitors and resistors at the input already attenuate most of the stadic discharge from the input jack - which is the main source of static charges in a enclosed circuit with proper shielding )

I don't have a 9.1v zener in hand so I tried a 1n4148 as shown in the previous diagram I post. So weird that it works. Can someone please explain on this?

Quote from: nguitar12 on April 17, 2015, 04:16:53 AM

Quote from: antonis on April 16, 2015, 07:25:06 AM
That's the way but you have to use 9V1 zener for mosfet protection from signal greater than 9V or negative...

( although I insist that BS170 DOES have internal zener protection and capacitors and resistors at the input already attenuate most of the stadic discharge from the input jack - which is the main source of static charges in a enclosed circuit with proper shielding )

I don't have a 9.1v zener in hand so I tried a 1n4148 as shown in the previous diagram I post. So weird that it works. Can someone please explain on this?

some reading:

http://www.diystompboxes.com/smfforum/index.php?topic=110503.0
http://www.diystompboxes.com/smfforum/index.php?topic=109494.0
http://www.diystompboxes.com/smfforum/index.php?topic=107093.0

Quote from: nguitar12 on April 17, 2015, 04:16:53 AM
I don't have a 9.1v zener in hand so I tried a 1n4148 as shown in the previous diagram I post. So weird that it works. Can someone please explain on this?

Transients at the gate of a MOSFET can kill it be either going more negative than the gate insulation can take, or more positive. The 1N4148 protects the gate against being pulled more negative than the source by turning on.

The 1N4148 in this circuit will not "zener" till more than 100V positive with respect to the source. So it cannot protect the gate against a positive transient. Most MOSFETs die about +/0 15V to +/-20V on the gate. A 9V zener stops the gate going more positive than about 9V, and so the MOSFET works OK from Vgs = 0V to 9V. Since the device only sees about 2-5V in this application, it works fine and the zener doesn't turn on either direction.

To sum it up, a 1N4148 works because it's a protection device, and it's not being engaged in either direction. But it provides protection only for negative transients, and no protection at all for positive transients. Find a zener.

If you don't have a zener, the base-emitter of a normal silicon NPN transistor usually "zeners" at about 5-7V of reverse voltage. Two NPN base-emitters connected in series with the emitters toward the gate of the MOSFET make a 10 to 14V zener and protect both directions. It is highly likely that in this circuit even one reverse-biased NPN base-emitter would be fine. Clip off the collector of the new "zener".

Thanks all. You guys are helpful