First Build: Screaming Meanie - Build Log With Questions

[rackstab]

Hey all.  I just started getting into building boxes from the ground up.  I've done a few pedal mods and thrown a kit together, but this is the first time I've gone to build a pedal from the schematic up.

I'm going to be building the Screaming Meanie from moosapotamus.net.  At this point, I'm learning how to read the schematic and source the components.  Here's what she looks like:


And here's the components list I've got from reading it:
D1 - LN4001 LED
C4 - 0.047 Cap
TR1 - 5k Transistor?
R1 - 2K Resistor
C1 - 2.2uf Cap
Q1,2 - NTE85 Transistor
Q3 - NTE123AP Transistor
R2 - 100K Resistor
VR1 - 10K Pot (x2)
VR2 - 250K Pot
C5 - 1uf Cap
C5 - 0.1uf Cap
R4 - 470 Resistor
R5 - 47K Resistor
C2 - 0.1uf Cap
R6 - 390K Resistor
R7 - 39K Resistor
R8 - 470 Resistor
R9 - 10K Resistor
1 Dual SPDT jack
2 mono jacks
1 power in
2 SPST switches

Reading the schematic, I can't quite follow three things:
A) Why are there two C5 parts with different values?
B) I'm assuming the TR1 is a transistor, but the Q designation is used for the other transistors.  Is this transistor being used for a different purpose?
C) I see SW2, which controls the on/off for the oscillation, but I don't see the effect on/off.  I'm thinking it's out of the schematic as a separate bit that you wire in yourself.  Like the power in and battery adapter, I assume?

I'm trying to get the components questions sorted prior to Wednesday, when I'd like to be able to order my components.  In the meantime,  I'll be harvesting parts out of an old Fender practice amp that's busted to hell, a CF bulb board, and some other stuff that would otherwise go to waste, as well as working out an enclosure design.  Is there anything that looks glaringly wrong so far?  Any hints of where I should look to get answers to the questions I have?

 

[J0K3RX]

A) The two C5's - That is probably a mistake just pretend it's C6
B) TR5 is a 5k trim pot
C) The wiring is standard - http://www.tonepad.com/getFile.asp?id=76

[Jdansti]

Also, you have D1 listed as an LN4001 LED. It's a standard 1N4001 silicon diode used for reverse polarity protection. The power indicator LED would be part of the off-board wiring that JOK3RX refered you to.

JOK3RX, do you know what's up with the "CV Pedal/DPDT switch"?

[Jdansti]

Apparently the "CV Pedal" is some kind of treadle controller. Here's the text from Moose's website:

If you don't like hearing the oscillator squeal as soon as it is turned on, the 5K trim pot (TR1) can be adjusted to silence the oscillator at the minimum frequency (VR1). That way, if you plug in a CV pedal and leave it positioned all the way back, when you switch the oscillator on, it won't be audible untill you start rocking the CV pedal forward.

[rackstab]

A) The two C5's - That is probably a mistake just pretend it's C6

Gotcha.  I was thinking that, but wasn't sure if it could've been a typo in the other direction with the value being wrong.

B) TR5 is a 5k trim pot

That makes perfect sense, what with the resistor symbol being right there.

C) The wiring is standard - http://www.tonepad.com/getFile.asp?id=76

Oh, cool deal then.  I was headed in the right direction!

Also, you have D1 listed as an LN4001 LED. It's a standard 1N4001 silicon diode used for reverse polarity protection. The power indicator LED would be part of the off-board wiring that JOK3RX refered you to.

Well, look at that.  I would've been confused if I'd ordered the part by number and expected an LED.  Thanks!

Looking more closely at my list, I think that should be a 3PDT and a DPDT switch, too.  Revised list is:
D1 - 1N4001 Diode
C4 - 0.047 Cap
TR1 - 5k Trim Pot
R1 - 2K Resistor
C1 - 2.2uf Cap
Q1,2 - NTE85 Transistor
Q3 - NTE123AP Transistor
R2 - 100K Resistor
VR1 - 10K Pot (x2)
VR2 - 250K Pot
C5 - 1uf Cap
C5 - 0.1uf Cap
R4 - 470 Resistor
R5 - 47K Resistor
C2 - 0.1uf Cap
R6 - 390K Resistor
R7 - 39K Resistor
R8 - 470 Resistor
R9 - 10K Resistor
1 Dual SPDT jack
2 mono jacks
1 power in
1 3PDT switch
1 DPDT switch

Thanks for the input.  Much appreciated!

[Jdansti]

BTW-Welcome to the forum! 

On your revised list, the diode # starts with a "1" not an "L".

Also, looking at the layout, I don't see "VR1", but there are "CV2" and "CV3" connection points. I'll IM Moosapotamus and see if he can help out.

[moosapotamus]

No need for VR1 to be on the layout - just connect lug 3 to "out" in the layout, lug 1 to ground, and lug 2 is the output.

NOTE: I did that layout a long time ago. The orange lines are not traces. Only the blue lines are traces. The orange lines represent components (resistors and the trim pot).

I think y'all have everything else sorted out correctly.

~ Charlie

[rackstab]

BTW-Welcome to the forum! 

On your revised list, the diode # starts with a "1" not an "L".

Thanks for the welcome!  I've revised my list and started doing more looking-into of the trim pot.  Is it necessary for this to be a trim pot instead of a knob of equal value?  I'm wondering if it would be useful in any way to have the pot out in the open (kind of like the bassballs mod).  If this can be useful, I'm betting I would have to make a few other changes, rather than just substituting a regular pot. 

No need for VR1 to be on the layout - just connect lug 3 to "out" in the layout, lug 1 to ground, and lug 2 is the output.

Bonus!  So the "out" position in the layout is the connection point for lug 3, and the output would be going to my foot switch, I assume. 

The CV jack has another VR1 component, and I was wondering: would this go jack sleeve to C5 to lug 1 of VR1, which is also going to ground, and lug 3 would be tip to CV3 on the layout, with lug 2 going to CV2.  Is this correct?  Also, is the CV jack grounded to the enclosure?

Thanks for all the help, guys.  This is making it a lot clearer for me to learn how to read these things.  I plan on getting the lion's share of stuff freed from the salvage pile this evening after work, and getting the order going Wednesday.  Depending on how much I collect, I may get some strip board from radioshack and get rocking sooner than later.

[Jdansti]

@Moosapotomus-
I just noticed the second VR1 pot on the schematic after Rackstab mentioned it.  One VR1 is shown at the Output and the other is shown at the cv jack. I assume that the one at the output is the volume pot and it connects to the layout at the "output" as you described above, but what about the one connected to the cv jack in the schematic?  Is this the pot inside the cv pedal?

[moosapotamus]

Thanks for the welcome!  I've revised my list and started doing more looking-into of the trim pot.  Is it necessary for this to be a trim pot instead of a knob of equal value?  I'm wondering if it would be useful in any way to have the pot out in the open (kind of like the bassballs mod).  If this can be useful, I'm betting I would have to make a few other changes, rather than just substituting a regular pot.

You can use a regular panel mounted pot instead of that trim pot without making any other changes (just like the bassballs mod ). But all it is really used for is to set whether or not you want to hear the screaming oscillator when you switch on the effect. See the quote from my webpage about what the trim pot does that Jdansti posted, above.

Bonus!  So the "out" position in the layout is the connection point for lug 3, and the output would be going to my foot switch, I assume.

Yup.

I just noticed the second VR1 pot on the schematic after Rackstab mentioned it.  One VR1 is shown at the Output and the other is shown at the cv jack. I assume that the one at the output is the volume pot and it connects to the layout at the "output" as you described above, but what about the one connected to the cv jack in the schematic?  Is this the pot inside the cv pedal?

No, when you plug in a CV pedal the pot is disabled and the CV pedal takes over.

Sheesh... I can't believe I left so many typos in that schematic.

The CV jack has another VR1 component, and I was wondering: would this go jack sleeve to C5 to lug 1 of VR1, which is also going to ground, and lug 3 would be tip to CV3 on the layout, with lug 2 going to CV2.  Is this correct?  Also, is the CV jack grounded to the enclosure?

Oooh... I did a pretty lame job of documenting this project. Sorry about that.
For starters, I should point out that the CV jack is a stereo switching type jack. There are a couple of illustrations and a short explanation of what a stereo switching jack is and how it works at the top of this webpage...
http://www.jumbosunshade.com/misc_docs/swd03.htm
The CV jack sleeve goes to ground, as does the negative lead of C5 and one of the outside lugs of VR1 (the VR1 that's attached to the CV jack ).
The wiper (middle lug) of VR1 goes to the tip switch on the CV jack, and the tip lug of the CV jack goes to the positive lead of C5 (cv2 in the layout).
The other outside lug of VR1 goes to the ring switch, and the ring lug of the CV jack goes to the junction of R2 and Q2 (cv3 in the layout).

I hope that helps. If necessary, when I get the time, I can make a wiring diagram to clarify the whole thing.

~ Charlie

[Jdansti]

Thanks Charlie!  If I understand correctly, the pot at the cv jack (I'll call it VR3) has nothing to to with the VR1 pot on the output. VR3  does the same thing as the pot in the cv pedal when the cv pedal is disconnected.  The stereo jack disconnects VR3 when the cv pedal is plugged in.  If you never want to use a cv pedal with the Screaming Meanie, then you could omit the stereo jack. Does all that sound correct?

[moosapotamus]

That's right, John.

~ Charlie

[rackstab]

You can use a regular panel mounted pot instead of that trim pot without making any other changes (just like the bassballs mod ). But all it is really used for is to set whether or not you want to hear the screaming oscillator when you switch on the effect.

Ah, gotcha.  I'll probably just leave it as is, then.

For starters, I should point out that the CV jack is a stereo switching type jack. There are a couple of illustrations and a short explanation of what a stereo switching jack is and how it works at the top of this webpage...
http://www.jumbosunshade.com/misc_docs/swd03.htm
The CV jack sleeve goes to ground, as does the negative lead of C5 and one of the outside lugs of VR1 (the VR1 that's attached to the CV jack ).
The wiper (middle lug) of VR1 goes to the tip switch on the CV jack, and the tip lug of the CV jack goes to the positive lead of C5 (cv2 in the layout).
The other outside lug of VR1 goes to the ring switch, and the ring lug of the CV jack goes to the junction of R2 and Q2 (cv3 in the layout).

Ohhhhhhhh, okay.  That makes a lot more sense than what I was thinking.  I was kind of lost for a second when I got here

The other outside lug of VR1 goes to the ring switch, and the ring lug of the CV jack goes to the junction of R2 and Q2 (cv3 in the layout).

But looking over here cleared up any questions I had.  I think I'm going to be ready to rock as soon as I get my parts in!  Thanks a bunch for the help, guys.  I've already started learning more than if I blindly stabbed around with no input.

[rackstab]

Alright!  Parts ordered and on their way.  I went ahead and substituted 2N3904 transistors for the NTE85 and NTE123AP, as everything I could see showed them to be equivalent.  I figured I was taking a shot in the dark on this, but it looks like the NTE transistors are just generic transistors anyway.  I'm thinking this shouldn't be a problem, but we'll see!

[Jdansti]

Good luck!

[moosapotamus]

2N3904 should be a good sub for NTE85.
Also try 2N5088 as a sub for the NTE123AP, if you're not happy with the 2N3904 in that position.

~ Charlie

[rackstab]

2N3904 should be a good sub for NTE85.
Also try 2N5088 as a sub for the NTE123AP, if you're not happy with the 2N3904 in that position.

~ Charlie

Good to know.  I grabbed a transistor medley from RadioShack for another project, so I might just try out a few different things and see what flies.  In other news, almost all of my stuff is already delivered to my house, and the last few bits needed should show up by Monday.  I'm stoked. STOKED! 

[moosapotamus]

FYI - I corrected and updated the build docs for the screaming meanie.

http://moosapotamus.net/meanie.html

... added a wiring diagram, too. So, everything should be good to go, now.

Sorry for any confusion. Thanks for pointing out the errors, y'all!

I must say, it's been a while since I played with it. What a nasty little box!

Thanks
~ Charlie

[Jdansti]

FYI - I corrected and updated the build docs for the screaming meanie.

http://moosapotamus.net/meanie.html

... added a wiring diagram, too. So, everything should be good to go, now.

Sorry for any confusion. Thanks for pointing out the errors, y'all!

I must say, it's been a while since I played with it. What a nasty little box!

Thanks
~ Charlie

Excellent! Thanks!

[rackstab]

FYI - I corrected and updated the build docs for the screaming meanie.

http://moosapotamus.net/meanie.html

... added a wiring diagram, too. So, everything should be good to go, now.

Sorry for any confusion. Thanks for pointing out the errors, y'all!

I must say, it's been a while since I played with it. What a nasty little box!

Thanks
~ Charlie

Well damn, lookit that!  I'm kind of glad I've been sick the past few days and unable to get started on this.  Thanks a bunch for the updates, moos.  Depending on how well I'm feeling, I may have some updates tomorrow evening.