Trimpot Adjustment - Son of Ben

[Chuck D. Bones]

Step 1. Check your spelling before hitting send.
Step 2. Verify your JFETs are actually good JFETs.
Step 3. Inspect your board for workmanship.

At one end of the trimpot travel, you should get close to 9V. At the other end, you should get substantially less, maybe something close to zero. If that isn't happening, there is something wrong with your pedal.

 

[Chuck D. Bones]

Bobb Lobblaw: do you know how to use a DVM?

I have to ask, because none of the wolves I know even savvy what a DVM is.

 

[music6000]

Yes, Co-sign this request!
Please can some one explain this process as if you were talking to a sixth grader raised by wolves in a national forest?

Hope this will get you there :

 

[Bobb Lobblaw]

I'm learning as I go, Chuck. The Wolves are pure analog, baby.

Thank you, M6K.
This is only my third build (not counting my failed Echo Nightmare), and I am definitely a newbie when it comes to metering and such, so I'm basically trying to learn it all at the same. But that's how I thought the process was supposed to go.
HOWEVER..
Here's the thing. Well, two things.
1) According to the datasheet of the installed "InterFet J201" the pins go 1) source, 2) drain 3) gate.(https://www.mouser.com/ProductDetail/InterFET/J201?qs=/ha2pyFaduh6EYvyYo4gV6ZjdGsoMaCrkP1C2KUJ4mQ=)

2) Unfortunately, that doesn't seem to matter because when I do as you so awesomely illustrated, (Meter set to 20 volts) I get no reading at all from any pin. Nada, zilch. Be it plugged in and (true) bypassed , plugged in and on. Unplugged...I just get nuthin'.
If it's plugged in and bypassed & I put the ground on the "source" (1) and the other on the drain (2) I get a reading that I can dial to "4." I have no idea if that is actually 4v or if it's just teasing me.

The pedal works and sounds pretty good. . But of course, if I can reach for the ULTIMATE TONE, man... I'd like to.
Interestingly, with the drive all the way down, I get no sound at all even with the volume cranked. I don't think that's supposed to happen.

 

[music6000]

I'm learning as I go, Chuck. The Wolves are pure analog, baby.

Thank you, M6K.
This is only my third build (not counting my failed Echo Nightmare), and I am definitely a newbie when it comes to metering and such, so I'm basically trying to learn it all at the same. But that's how I thought the process was supposed to go.
HOWEVER..
Here's the thing. Well, two things.
1) According to the datasheet of the installed "InterFet J201" the pins go 1) source, 2) drain 3) gate.(https://www.mouser.com/ProductDetail/InterFET/J201?qs=/ha2pyFaduh6EYvyYo4gV6ZjdGsoMaCrkP1C2KUJ4mQ=)

2) Unfortunately, that doesn't seem to matter because when I do as you so awesomely illustrated, (Meter set to 20 volts) I get no reading at all from any pin. Nada, zilch. Be it plugged in and (true) bypassed , plugged in and on. Unplugged...I just get nuthin'.
If it's plugged in and bypassed & I put the ground on the "source" (1) and the other on the drain (2) I get a reading that I can dial to "4." I have no idea if that is actually 4v or if it's just teasing me.

The pedal works and sounds pretty good. . But of course, if I can reach for the ULTIMATE TONE, man... I'd like to.
Interestingly, with the drive all the way down, I get no sound at all even with the volume cranked. I don't think that's supposed to happen.

Here is the Correct pinout for the J201 Transistor:

 

[Robert]

1) According to the datasheet of the installed "InterFet J201" the pins go 1) source, 2) drain 3) gate.

Do you by any chance have one of those that is not installed in your pedal? I'd be curious to know what sort of resistance measurements you get between the Source / Drain pins and the Drain / Gate pins, as indicated in that datasheet.

It's certainly not impossible that InterFet changed the pinout, but this is the first I've heard of it.

 

[music6000]

It appears Interfet have reinvented the J201 with their own Pinout if you follow the same basic shape, 3. Gate 2. Drain 1. Source
In order for it to work with the Original Standard J201 Pinout, 1. Drain 2. Source 3. Gate , It has to be flipped 180 Degrees!
The Drain & Source are interchangeable so it should work after this Mod!

 

[Bobb Lobblaw]

Ahh, crap on toast..
So I have to remove them from the PCB, flip them and resolder "backwards?"
Well, there goes my pretty wiring job.
OK, I'll give that a shot, thanks very much.

 

[Chuck D. Bones]

No, don't remove any parts. If your pedal is working then there is no problem with the FETs. You don't need a DVM to fine tune the FET bias, it's only used to get you in the ballpark. Adjust by ear. Start with the one next to Q3, then Q2, then Q1. Make at least two passes. The adjustments can be pretty subtle, so take your time. The Q3 trimmer also affects the TREBLE control tuning.

To respond to your other questions & comments:

The sound should go away if you dial DRIVE down to zero. Some pedals do this, some don't. The SoB was designed to kill the signal when DRIVE is set to zero.

Sounds like you need to practice using a DVM so you can use it with confidence and believe your readings. We're not really running a school here, try YouTube.

 

[Bobb Lobblaw]

Yeah, I know, Chuck.
"Electronics for Dummies" is sitting in my Amazon cart.
One more thing. Just out of curiosity, you say Q3 affects the treble control, what do the trimmers for Q1 and Q2 do?
And, Thanks again, my solder sucking aren't great.

 

[Chuck D. Bones]

I said the Q3 trimmer also affects the treble control. The purpose of the trimmers is to set the drain voltage on their respective FETs. The trimmers are necessary because JFET specs are pretty loose and most of us don't cherry pick our JFETs.

Hey, we all had to start somewhere.

 

[Thewoodenone]

I can't get over 1.1V and I tripple checked components and solder. I did change the value of trim 1 so I could get 2k easier. What am I missing?

 

[Thewoodenone]

Here is the gut shot

 

[Chuck D. Bones]

The good news is your JFETs are in sockets. Try pulling them out and measuring Vp and Idss.

 

[soothsayer86]

Here is the Correct pinout for the J201 Transistor:

View attachment 4342

I just checked the datasheet for the interfet j201 https://www.mouser.com/datasheet/2/676/jfet-j201-j202-interfet.r00-1649170.pdf, and it is definitely labeled 1)Source 2)Drain 3)Gate. Did anybody figure out whats going on there? I have a SoB on the "to-do" list.

 

[Thewoodenone]

So my DMM that was able to quickly check transistors got fried when I let a friend borrow it. Long story but he is lucky to be alive. I'm not sure what this is "supposed" to sound like but as it is it sounds JUST like an Orange amp. After tweaks its no different voltage wise but I'm hesitant to change anything. What is it supposed to sound like? BTW I got 2 J201s from NOS and 1 from Tayda.

 

[Chuck D. Bones]

Unless you measure Vp & Idss, you don't know if they're the real deal or not. If you can't dial in the drain voltage, then something's amiss. All that doesn't really matter if you like the sound.

 

[soothsayer86]

If anyone has used SMD j201's for this project would you mind posting a picture so I can see your method of socketing them? Would really appreciate it since its the first time I will be using the adapter boards. Thanks

 

[bassmancharlie]

If anyone has used SMD j201's for this project would you mind posting a picture so I can see your method of socketing them? Would really appreciate it since its the first time I will be using the adapter boards. Thanks

I have. I’ll post a picture soon ?

 

[soothsayer86]

I have. I’ll post a picture soon ?

I just went for it and it worked out ok. But feel free to post your pictures still as a resource to others who might need it!