Help with Transistors

[Laguna]

Hi Guys!

I'm new in the forum and also new at this. I know that a couple of you will read this and say "oh, he's a noob" and yes, you're right
The thing is I love music and I like math, so I started learning about making pedals.

Let me post the question first, and then i tell you about what i was doing so you can skip that part if you want

I couldn't get J201 or 2n5457, I read in this same forum that somebody used NTE468, so i got some of those (and some NTE467, just in case the other one didn't work for me)
This is the data sheet: http://www.nteinc.com/specs/400to499/pdf/nte468.pdf

I tried building the alembic stratoblaster:
http://www.freeinfosociety.com/electronics/schemview.php?id=1192

Well, it didn't work: basically the maximum output i could get was less than the output directly from my input.
The pot DID work, but again, always LESS output than the original.
I double check all the measurements with my multimeter, the only thing that could be wrong would be the transistor. Maybe i plugged it wrong?
I reversed the transistor just to test and then i got no output. Ok, i put it back.
I tried it with the NTE467 and got the SAME results.

Then i removed the caps, as far as i understand, those are for filters, so testing without the caps should be fine for a quick test.
Of course, the result was the same. Lower output than the original input.

I tried lowering the input resistances, and remove the volume pot for maximum volume.
Here i was able to get the output to almost the same volume as the input.
I removed more stuff to get to the BASIC super BASIC circuit. Still got the same result as the previous test.
I'm sure i'm doing something wrong. Probably i have to do something now because i used a different JFET?
I thought the difference could only be on the gain and the maximum voltages (again, i'm a noob here, feel free to correct me ). I can ONLY use J201 or 2n5457??? the NTE468 just is a useless JFET? i'm sure I'm the one doing something wrong

Can you point me to the right direction? i don't even know where to start looking.

Here are the links:
https://ibb.co/crD0XJ   ==> Stratoblaster
https://ibb.co/fJ0Qzy   ==> Basic test that didn't work

What you can't see, very basic:
Left: Input
Right: Output
Top: Battery terminals

Oh, i did try with 2 batteries, one 100% new.
I did measure the battery too, 8.9v and 9.15v (I tried 2 )

Thank you guys, I appreciate the help.
I think that probably replacing the NTE for a J201 would work, but why?!?!?! that's what's haunting me.

[Sooner Boomer]

The biasing on the input will affect the way the FET clips.  Check out http://www.runoffgroove.com/fetzervalve.html#11
for some ideas.  Reading the entire article would be good.  Hope this helps...

[tonyharker]

jfets are funny beasts. Even within the same type numbewr there are great variation in the parameters.  The NTE transistor you chose is quite different to the ones quoted for the circuit so I am not surprised it didn't work.  The parameters which vary are the gate-source cutoff voltage Vgs(off) and the Drain current with no voltage on the gate Idss.
The Vgs(off) for the j201 is between 0.3 and 1.5v and that for the NTE468 is betwen 3 and 10v.
Similarly the Idss for the j201 is between 0.2 and 1mA and that for the NTE468 is a minimum of 20ma with no max stated.

As circuits are designed with these in mind it is alwase wise to use the stated devices.

[Laguna]

ohhhhh!!!!!! i get it!

So, the NTE457 (https://www.frys.com/product/1800311?site=sr:SEARCH:MAIN_RSLT_PG) would be a lot closer to the J201 than the one i'm using.
I'd love to get my hands on J201, but i really have no idea where to find those. The NTEs are easier, i just drive half an hour to FRYs and get them.

I thank you both for your replies, I may try with an NTE457 and tell you how it goes (what's the worst that can happen? i spent $2?) and also try to get a J201 or 2n5457 nearby.
Amazon takes like a month to ship!

Thank you again!

[pinkjimiphoton]

make sure your pinout is right, too.
in my experience, nte stuff usually won't work without some circuit tweaking.

i remember my first fuzzface, built with nte equivs. amazed i got any sound out of it at all. it was more like a loud slightly dirty compressor

[Laguna]

Ok, so, i went to Frys and got my NTE457s. The NTE458s are $8!!!!!! Are they crazy?
Anyways, i built the original circuit and... same results (lower output than original)
I strip it to the bare minimal and... same results
I played with the resistances (lowered the bias and input resistances) and... was able to get at most the same output than the original.

As the NTE457s have 0.5 to 6v Vgs(off) (Thanks Tony!) i thought it was going to work.. but no :S
I could order some 2n5457s but they are going to take like a month to arrive, but i'd love to know if you know what kind of tweaks i should be doing to make it work with the NTEs?

@pinkjimiphoton: i did read the specs for the NTEs, but TBH, they are confusing on the pinout
https://www.frys.com/product/1800311?site=sr:SEARCH:MAIN_RSLT_PG

The screenshot doesn't show me if they are with the round or flat facing forward. I guess i only tried with the round. I'll try tonight with the other side facing forward. See what happens.

[bluebunny]

The screenshot doesn't show me if they are with the round or flat facing forward. I guess i only tried with the round. I'll try tonight with the other side facing forward. See what happens.

That's flat-side forward (top), and the view from below (bottom).

[Laguna]

HAHAHAHAHA great, then i put it backwards!
I thought that was the round side

[duck_arse]

Laguna, seeing as no-one else has said, welcome to the forum.

can you show us your circuit diagram please? the bare bare minimum you should have is the jfet, three resistors and two capacitors, one at the input [gate] to block DC FROM the outside world, and one at the output [drain] to block the DC GOING to the outside world. then you can worry about vol pots et al.

there is never any point in "trying it the other way round" because you always have the datasheet to provide the correct pinout for your part at hand before you start. put it in the right way the first time, and cross that possible fault off your list.

also, for our circuits, all your jfets can swap the Drain pin for the Source pin. but the gate is always the gate. for a centre-gate package, like the K30A [a good replacement for j201 or 2N5457], you can rotate them because the pinout is effectively symetrical.

ahhh, I just checked your circuit diagram linked, and it has an error. there is no gate bias resistor, from gate to ground, try fitting anything from 470k to 4M7. this should get you back on track. also, another vote for the fetzer pages at ROG.

one last thing, re the bluebunny diagram above - IF the [any] package drawing shows the pins, it means you are looking at the pins. you can't see the pins thru the plastic, so it is not a top-down view.

[Laguna]

Thank you Mr Duck!

I'll try that tonight.

"Put it in the right way the first time, and cross that possible fault off your list." ==> of course man, but this is the first time i'm seeing this kind of diagrams and i didn't know which part was the front

I'll try it again tonight with that bias resistor!

Thank you! and thank you for the warm welcome

PS: "another vote for the fetzer pages at ROG" ==> i don't know what this means

[idy]

ROG is "Run Off Groove", www.runnoffgroove.com. They have project pages for many FET circuits, amp simulators famously. The Fetzer Valve is a using method of adapting tube circuits to FETs.

[Laguna]

Guys!!! It worked!!!!
It looks like I didn't try the 457 both ways because... Well somehow I was sure that the picture indicated that the front was the round part :-P
With the previous ones I did try both ways but it looks like I didn't with the 457

The gate bias resistor was not needed to make it work but it did reduce some noise!

I'm going to be finishing my pedal soon and I'm happy as a clam

Thank you again, all of you!

And if a noob like me reads this:
1) nte468 is not a good replacement. Try nte457
2) if you can only get some volume lower than your input, check if you have your transistor wrong. Some specs are tricky for noobs

Have a great day

[POTL]

now you can buy J201 in smd package.
They are cheap and it seems to me that they are more like each other than the old ones in to-92.

[duck_arse]

nice work Laguna, but keep the gate to ground resistor fitted, the higher values better. if you remove it, strange things will start happening, pedal works for a while, then stops, pedal farts and blurts, then stops, but mainly - Laguna, an unhappy clam.

[Laguna]

Yes, i left the resistance in. It's a 1M ohm (i didn't have 5M at hand ^_^)

I'm already using it and at 3/4 boost, it sounds really great on my dirty Blackstar! \m/

Now, I have a different question, something i didn't even think about: It works great from a 9v battery, but it doesn't work out of my multi-pedal power supply. Maybe something has to trigger the voltage? any thoughts?

Thank you guys, and let me know if you want some pictures

[bluebunny]

. . . let me know if you want some pictures

It's the law.   

[Laguna]

I'll open it and take another pic for you guys then

It looks bad, but it's my first (well, i made a passive volume box too)

[Laguna]

Ok, so, for the noobs like me, here goes something, the reason why my pedal works with the battery and not with the power supply is because the power supply has the inverse polarity as the standard battery clip.

Right now i'm using it with a cable-adapter that inverts the polarity ^_^

I thought about doing a diode bridge to correct the polarity. I may do that for my next project.

[bluebunny]

Wow, where's your power supply from?  I'd find it hard to buy one that didn't follow the Boss-style centre-negative "standard".  BTW, a diode bridge won't invert your power supply.  I don't know why you'd want to: your circuit is negative ground, and it works fine this way with the battery.  It's just your power supply that's "wrong".  Just use the adapter as you're doing already (although this just hides a problem that will bite you sometime in the future).

[Laguna]

I checked my power supply and it has the negative in the middle, it's backwards from the battery clip I have (?).

Well, that makes it easier!
Anyways, here's a picture of my stratoblaster from inside, yes, it's definitely not clean ^_^
Next one will be cleaner (i hope).

I also learned that i shouldn't just buy pots, i need to check the sizes of everything, the DC adapter I used was HUGE (same with the pots). And I couldn't fit a switch on the box i wanted to use