J201 Sourcing

[rankot]

How EXACTLY it doesn't work?

Are you some tough internal auditor guy or what, Ranko..??

No, I just couldn't find the description of the problem, but now I see it.

Question to freshmex18 - did you try to test your JFET devices with some kind of transistor tester? Does it see them as JFET, or not? If it does, then you must be sure you soldered them correctly to the adapter (if using that). Then, test them again, this time put the adapter with JFET into tester. If it works well with tester, then check again if you put it right on PCB. Go have a coffee and check again.

[soggybag]

A schematic with some voltage readings would tell us a lot. It would narrow and possibly pinpoint the location of the problem.

[PRR]

A schematic with some voltage readings would tell us a lot....

https://www.diystompboxes.com/smfforum/index.php?topic=128553.msg1238693#msg1238693

[freshmex18]

I have successfully built a Big Muff, SHO, Naga Viper, Solodallas Storm, Distortron, Les Luis, TD-X, CB30, Rockman, and A Bluesbreaker from vero layouts; a Super Stevie, a Soloist, and a KOT from PedalPCB boards, and a CE-2 and a univibe from Madbean boards.  So I can make some circuits work.  But of all of the projects I have tried and failed to build, the only common factor in all of them is that they were veros and that they used J201s.  And since I can successfully build from vero layouts, I'm thinking it has to be the J201s

I built the Plexidrive three times from two different vero layouts and no good.  I built the ROG Uno from two vero layouts and one point-to-point layout and no good.  I built the Brittania from a vero and from the 1776 board and no good.  The only thing common is the ten or so J201s that I used in every one of these builds.

The PedalPCB adapters correct the pinout of the SMD

Some of the layouts had voltage readings and I was able to use the trimmers to bias the first few but by Q3 or Q4 I could not bias for voltage.  Not one of these circuits had signal coming out of the output wires so no sound when connected to a guitar.  I did not put specifics for one non-working build because it is a problem across multiple builds and because none of those builds are together currently as I tossed them a year ago and was going to start from scratch again with new J201s

So that is why I originally asked where users here have been sourcing their J201s so I could get some from the same sources and try to build these projects again.  If there is still an issue with a specific build, I can post specifically about that one build at that time.

I do not have a tester beyond the jig I linked above.  Does anyone have a tester they recommend I use?

[antonis]

Am I the only one who feels negative treatment..??

@freshmex18: Nobody criticized your building skills as well as nobody cares about the number and difficulty of your particular builds..
Just do us the favour by posting some voltage readings of any J201 non-working circuit you refer on, plz..

[rankot]

I have successfully built a Big Muff, SHO, Naga Viper, Solodallas Storm, Distortron, Les Luis, TD-X, CB30, Rockman, and A Bluesbreaker from vero layouts; a Super Stevie, a Soloist, and a KOT from PedalPCB boards, and a CE-2 and a univibe from Madbean boards.  So I can make some circuits work.  But of all of the projects I have tried and failed to build, the only common factor in all of them is that they were veros and that they used J201s.  And since I can successfully build from vero layouts, I'm thinking it has to be the J201s

I built the Plexidrive three times from two different vero layouts and no good.  I built the ROG Uno from two vero layouts and one point-to-point layout and no good.  I built the Brittania from a vero and from the 1776 board and no good.  The only thing common is the ten or so J201s that I used in every one of these builds.

The PedalPCB adapters correct the pinout of the SMD

Some of the layouts had voltage readings and I was able to use the trimmers to bias the first few but by Q3 or Q4 I could not bias for voltage.  Not one of these circuits had signal coming out of the output wires so no sound when connected to a guitar.  I did not put specifics for one non-working build because it is a problem across multiple builds and because none of those builds are together currently as I tossed them a year ago and was going to start from scratch again with new J201s

So that is why I originally asked where users here have been sourcing their J201s so I could get some from the same sources and try to build these projects again.  If there is still an issue with a specific build, I can post specifically about that one build at that time.

I do not have a tester beyond the jig I linked above.  Does anyone have a tester they recommend I use?

Honestly, I've sourced my JFETs mainly from Aliexpress and they all worked as intented, if they really WERE JFETs (sometimes they send ordinary NPN, but it's easily solved with a refund).

I also bought few from Mouser and they also worked well.

THERE'S NO REASON your circuit won't work if you tested what I told you to test, presuming everything else is fine. Just make sure you check it and once you're sure your JFET is OK and oriented OK, go checking other components. Murphy never sleeps!

Regarding tester, you can buy something like this for 20 bucks - https://www.amazon.com/Assembled-Transistor-Capacitance-Frequency-Generator/dp/B08BYGH6TX - not perfect, but solves a lots of trouble. Or simply build a JFET testing jig like shown in http://www.runoffgroove.com/fetzervalve.html.

[moosapotamus]

The PedalPCB adapters correct the pinout of the SMD

But you tried flipping over your SMD J201 on the adapter for at least one of those projects, just for jollies, right? 

[Rob Strand]

Some of the layouts had voltage readings and I was able to use the trimmers to bias the first few but by Q3 or Q4 I could not bias for voltage.  Not one of these circuits had signal coming out of the output wires so no sound when connected to a guitar.  I did not put specifics for one non-working build because it is a problem across multiple builds and because none of those builds are together currently as I tossed them a year ago and was going to start from scratch again with new J201s

So that is why I originally asked where users here have been sourcing their J201s so I could get some from the same sources and try to build these projects again.  If there is still an issue with a specific build, I can post specifically about that one build at that time.

If you post the voltages there's plenty of people here who can diagnose what is wrong.    This is especially true on something like the Plexidrive where there's three stages as it shows a pattern.
There's plenty of other causes: 
- JFET parameters are off.   Often it's possible to tweak something to correct the situation.
- Pin out issues.
- and sure the JFETs aren't JFETs.

From the point of view of the DMM a JFET looks like this:



You can can use you DMM to work out the JFET gate.   
The resistors in the pic are part of the JFET.  They have a low value and don't affect the diode test.
- Set the DMM to diode range
- Find the pin which gives a diode drop to the other two pins.  Perhaps around 0.7V to 0.75V, a bit higher than BJTs.
- Also also need to confirm when you reverse the leads there is an open reading (DMM will show 1___ or OL).

The pin which fits that pattern is likely to be the JFET gate.   However if the part is actually a BJT it could also be the base of an NPN transistor.

Next set the DMM to the 2k range.
- Measure the resistance between the other two pins.
- reverse the meter leads, and measure between the other two pins again
- A JFET should measure more or less the same value in both cases and the resistance
  should be less than 2k.
  You can do slightly better than this by touching the gate (the pin we have already identified previously)
  to one of the other pin and you should see the resistance reading drop went you touch the pin.
  With the pin touching, the resistance will be less than 100 ohm for switching JFETs and
  perhaps 200 to 400 ohm for standard JFETS and perhaps about 600 ohms or so for J201.
- If the part is BJT then, without touching the pin one next to it, it will show an open circuit
  in both directions.

[freshmex18]

Maybe I am misreading the tone of some of the comments here.  The general sense I am getting from them is that the problem HAS to be my builds because J201s work just fine. 

I listed my successful builds to show that I have built things that do not require J201s

The likelihood of me being able to build non-J201 things correctly and every single J201 build I attempt is a faulty build on my part is incredibly unlikely.  Especially when I am building from a prefab board like the Brittania from 1776.  Of course I have made mistakes on other builds and spent hours troubleshooting only to find a microscopic solder bridge or a component off by one hole.  I make mistakes.

I will order some new J201s from the commented sources and get an tester and attempt a specific build and make a post on that one specific build if it doesn't work so I can give voltage readings and such

Thank you for your help

[Rob Strand]

Maybe I am misreading the tone of some of the comments here.  The general sense I am getting from them is that the problem HAS to be my builds because J201s work just fine. 

Absolutely not!

When things don't work there's a process to work out what is wrong.   The process is about narrowing down the problem and identifying the cause.  It's about knowing the cause and not blaming without any evidence.   There's no denying suspect JFETs have to be put on the list.   If the JFETs are out of spec then it's often possible to make some tweaks.   If the JFETs are actually BJTs then its possible to work that out as well.

Measuring voltages and checking parts is pretty common.   I've done this stuff a long time and I still do that.

[garcho]

Imagine going to a construction site and a carpenter is swearing up and down that the nails are the problem, while the rest of the carpenters are swinging away. Yes, maybe it's the nails, but no, it's probably not.

I've been working as a musician and engineer for many years (20+). Last week I was giving an initial test to a new mixing board and was cursing it because the aux sends "weren't working". I had grabbed a TS cable instead of a TRS. Embarrassingly, I spent almost 30 minutes f***ing with it, testing everything else pointlessly, assuming it was the gear, before I realized the doofus error I made. You know how I finally realized what it was? Because someone else said "Hey, you're using a balanced cable, right?" Don't get offended, just make it work.

[freshmex18]

OK, look at it from my point of view. I started a thread asking where people on this site source their J201s and most replies were not telling me where to get them.  While I know I am a noob and not as knowledgable as most on here, I was pretty clear that I do not have those builds currently so I could not give voltage measurements or take pics.  I want to rebuild those projects and I want new J201s to do that.  I don't want to use my current supply as I suspect they are the issue.  When I rebuild with my new J201 supply and they don't work, then I will be sure that the problem is me and not the components.  But with comments telling me that the problems are not my current J201s or that I should stick to simpler builds or asking me for measurements I can't give currently instead of answering my question, I am not feeling like this is the right community for me to post to as this has not been a particularly welcoming experience.  I appreciate the effort from those of you who tried to help me troubleshoot and I appreciate those of you who gave me some sources of places to get new J201s and a tester and I will be purchasing those soon.  Thank you. 

[soggybag]

I meant no disparagement of you or your ability. If I could see a schematic, I could understand the context, and if I could see the voltages at Gate, Source, and Drain it would say a lot about what's going. It's like a fresh set of eyes on the problem. Without that information we're all flying blind!

[PRR]

Just tell him where to buy good JFETs! I agree that there has not been enough of that in this thread.

[rankot]

Just tell him where to buy good JFETs! I agree that there has not been enough of that in this thread.

I told him that I bought my good JFETs at Mouser, the same place he did. Also bought a ton of them on Aliexpress, and most of them work just fine.

So, obviously, it's not the problem with the JFET source, but something else.

[Rob Strand]

Mouser is a good FETa sauce because Mousers like cheese.

https://www.myrecipes.com/recipe/feta-sauce

[niektb]

To answer your original question, I sourced SMDs with adapter from Tayda and they worked fine for me!

But if theyre out-of-spec then in the most cases you would still have sóme sort of sound (even though it might sound bad). If there's no sound at all I would suspect a pinout issue or maybe a build issue  you know, I stumbled across a very similar issue in the past, had a build where J201s wouldn't work but 2N5457 would. Both SMD, both using a SMD to TO-92 adapter. But guess what? The pinout of the J201 wasnt the same as that one of the smd to tht adapter 

[anotherjim]

Most ROG circuits have drain trimmers which reduces the chances FET variations within the specs as an issue. I think they would have to be bad or fake FET's to not work to some extent. If from a reputable source, we can rule fake out.

I mentioned earlier the possibility of the smd adapter putting the gate on the wrong pin to match the thru-hole part. If that isn't confirmed I don't see the point of any other discussion.

This one puts the gate in the middle which won't work without crossing the connections or redesigning the board layout.


This one corrects the gate to one end (pin3).

[antonis]

Mouser is a good FETa sauce because Mousers like cheese.
https://www.myrecipes.com/recipe/feta-sauce

Reduced-fat feta cheese is NOT a ΦΕΤΑ..!! 
(take my word..)

[amz-fx]

Here is a fast and simple fet test setup. All it requires is the jfet, 3 resistors and a battery. Use a dc voltmeter to measure the voltages.

Connect the 9v battery and measure the dc voltage from +9v to ground with the meter, just to confirm the power source. It is usually slightly above 9v with a fresh battery.

Now move the positive (red) probe from +9v to the + output... you are measuring the voltage across the 10k source resistor here. It should be around 4v or slightly over, depending on your battery voltage. The gate-to-ground voltage should be around 4.5v (or slightly over).

Report your measurements and the people here will help analyze what is going on.

Best regards, Jack