EA Tremolo 100k Trim Pot, and Jfet question

[Fndr8875]

Im using this layout.

http://tagboardeffects.blogspot.com/2012/02/ea-tremolo-modified-rog.html

First question is i dont have a 100k trimmer on hand, local radioshack is out of them, and i perfer the bourns trimmers to these kind, idk exactly what there called seems like ive seen them both called cermet. But i do have a 7805 5v regulator. I know jfets and such vary widely in there ranges but i dont think thats why the trimmer is used in this circuit. Would the regulator work until i get my trimmers delivered, or just instead of the trimmer. It says to dial it from 4.5 to slighly above 5v from what ive read. Also why couldnt I use 2 Bs170s for q1 and 2, with this layout using a j201 or mpf102 or 2n5457 the pinout is different and you have to bend the pins around. Theres alot of things ive tried to figure out on my own such as these but it just doesnt click. I only have a couple of each of the FETs and ive read they are sensative so dont wanna go throwing ones in and out of socket and fry them. Any replies much appreciated.

[Transmogrifox]

The 100k trimmer makes bias easy, but you can also get there with hard-wired resistors.  A good starting point would be something like this:
9V->270k->100k->GND
The 1M from Q1 goes between 270k and 100k.

You can use BS170 for Q1, but it won't sound right if you use it for Q2.

You don't need to bend the pins around to use a 2N5457.  All you need to do is make a minor change to the layout to accommodate this.  Maybe I'm overestimating your skill level, but to me it seems like a viable option for most builders -- it's mostly an accounting job to make certain that you swap everything on a given pair of traces.

You won't fry FETs in this circuit by putting them in wrong.  You will fry FETs with ESD.  Just handling the board to pick it up and box it puts them at just as much risk of being fried as swapping them in and out.

For ESD keep the board grounded and touch the ground with whatever hand is not holding the FET before you try to place the FET into the circuit.

I have fried a lot of FETs being careless about ESD when breadboarding circuits.  Just part of tweaking, but most of it can be avoided with a little bit of care to discharge yourself before touching components.

[Fndr8875]

I wish i had the ability to rework the circuit to the DSG pinout could go straight in without bending the legs. Ive got everything soldered up just have to solder pots in and then offboard wiring. Could you give me a rough idea of where in the circuit i would modify to be able to drop FET straight in? Im not asking you to figure out values  just a rough idea of which resistors? Ive always been terrible at math, and have dsylexia, lol, when i first started doing this and tried pad perhole layouts I would try for hours to build simple circuits and it was just a nightmare, anyway I could always just order one of the FETs listed on layout. I think one reason i am so obsessed with this hobby is still not understanding certain things and ive always loved pedals and was fascinated by them when i was young, and want to be able to gain that understanding, but it sucks going over and over and over explainations of things just to be left scratching my head. Thanks again for reply

[Transmogrifox]

Good thing this doesn't require any math, but dyslexia certainly puts a twist on things that would otherwise be simple

So what you want to do is orient it so Q2 goes GSD, top to bottom instead of DGS as shown.

There are only 2 things you need to do to make this work:
Move Depth 2 wire up 1 row
Move 22 uF capacitor lead down one row.

For the 22 uF capacitor you will just have to bend the lead over to Q2 Source and solder leads together on the bottom.  Make sure the cut on that trace removes that whole pad/square so the cap lead doesn't touch the other side.  If in doubt just make a continuity measurement from Q2 Source to Q3 Base when you're done to confirm there isn't an accidental connection.  No real big deal there.

You may notice my suggestion reverses Drain and Source connections.  Don't worry -- I did that on purpose to make this easier -- because drain and source orientation is irrelevant in this circuit.  All that matters is you have one connection to ground and one to the 22 uF cap and the pot connected to the gate.  My suggestion will get you there without very much re-work.

[Fndr8875]

Sweeeet!!! Thanks for your help! I was planning on finishing it up tommorow so ill make those two mods and report back. I wish i would have just done the Heart Throb trem, no JFETs and seems everyone who has built that is happy with it. But when searching for a Trem project the EA trem was everywhere, perf, vero, PCBs every medium there is, so i figured it was the best one. Seems that all the demos out there have some kind of switchable boost or something different than this one, and ive beeen wanting a Tremolo for a while anyway thanks again for your help, i was able to get a 2n5457s pin bent and socketed but there wouldnt have really been any room to trim the legs so woulda been a tight fit. Now i can try out j201, 2n5457, and a MPF102 to see which one sounds best. You say that youve fried JFETs before by just handling them, I bought two from small bear and they have been in package ever since. I picked up some DOD death metal from a pawn shop for 9 bucks several months back just to see what i could part out in it, ended up with like 6 5088s and 6 j201s. Long story short I recently got one of these MEGA328 testors off ebay

http://www.ebay.com/itm/12864-Mega328-ESR-Transistor-Resistor-Diode-Capacitor-Mosfet-Tester-w-Test-Hook/391483734884?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3D3c3f473318d54d0b827ae20c7e855ec8%26pid%3D100005%26rk%3D4%26rkt%3D6%26sd%3D321963237498

And all the j201s i test show as CBE pinout. Including the smallbear ones that remained in package and were never touched until now, seemed odd. Hopefully they are all good, the 2n5088s i salvaged match up and hfe range is good, and i have used before and they worked fine. im rambling, but thanks for your help!

[Transmogrifox]

Your tester description does not mention JFETs so good chance is it's trying to test the diode junctions as if it were a BJT transistor.  Just doesn't know how to test JFETs.

Use the datasheets for the JFETs to determine the pinout, not a tester that isn't designed to test JFETs.

Your ears will tell you if a JFET is bad. You will either get terrible noise, throbbing or just no tremolo effect if it's bad or if you got the pinout wrong.

FYI there is a very big difference between a MOSFET and a JFET.  They are as different from each other as a BJT is different from a MOSFET so don't cause yourself to think that a MOSFET and BJT tester knows something about a JFET.

That tester knows MOSFETs and BJT's because it's programmed to identify the difference between the 2, not because there is very much in common between the 2.

[PRR]

> Just doesn't know how to test JFETs.

That's pretty lame. (I do agree with your assessment.)

First-look, an N JFET could be an NPN. But strap "B" to "E" and you find ~~1K between "C" and "E", not infinity. So they just didn't care.