Lithium Grim OmniScreamer Instruction Manual

OmniScreamer
Building instructions
v1.0

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
2
Table of contents
PCB layout ............................................................................................................................................... 3
Introduction............................................................................................................................................. 4
Configurations and components............................................................................................................. 5
Pots...................................................................................................................................................... 5
Build sequence ........................................................................................................................................ 6
Off board wiring ...................................................................................................................................... 7
Potentiometers.................................................................................................................................... 7
External Diodes configuration............................................................................................................. 9
Modifications........................................................................................................................................... 8
OpAmp............................................................................................................................................... 11
Transistors......................................................................................................................................... 11
Troubleshooting .................................................................................................................................... 11
Schematic .............................................................................................................................................. 12
Read this entire manual thoroughly before you start building the effect! There are some available
options and you should choose which one you want to incorporate before starting your build.
Last update: 17-07-2019

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
3
PCB layout
Dimensions: 49,5 mm x 49,5 mm
1,95 inch x 1,95 inch
Soldermask mistake! Should be D5

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
4
Introduction
Before we start with the component list, it might be interesting to know how this PCB was designed.
Strictly speaking, you can break down this tubescreamer into 5 main sections and 3 optional mods.
The main sections are:
1. Input buffer
2. Output buffer
3. Main clipping stage
4. Tone/Volume stage
5. Power section
Both the input (1) and output (2) buffers are made switchable, so I would suggest to add them and if
you do not like them, you can just switch them off.
The main clipping stage (3) is where the most fun is at. Most tubescreamer based effects will have a
wide variety of clippingdiode configurations. In this manual you will find a lot of these configurations
will be explained and you can always decide to “mix and match”. A tubescreamer is an extremely
“modable” effect.
The tone and volume stage is built to fit almost all types of tone controls as found in a lot of
tubescreamer based effects.
The power section is not that interesting, but some versions use an a-symmetrical voltage divider to
form Vref. The only non-standard is that the polarity protection is changed to a (safer) serial
connection. This has no tonal effect what so ever!
The optional mods:
1. Boost
2. Offboard Clipping diodes
3. Feedback loop
All these mods can be added to any version you want to build! In the separate configurations sheet
you will find which mod is standard for some of the configurations and which are not. Again you are
free to add these mods or leave them out.
The boost mod (SW3) is a mod found in the Tim™. The off board clipping diodes switch (SW5) can be
used to add extra clipping diode configurations instead of (or in addition to) the onboard clipping
diode section. The feedback loop (SW6 and R22) will reduce the overall gain and brightness
depending on the capacitor that is switched in the circuit.
You should also take a look at the Electrosmash Tubescreamer dissection. It has a more in-depth
analysis (note that it also covers the JFET foot switching that is intentionally left out of this PCB)
The components needed for the different type of effects can be found in the separate configuration
sheet (pdf).

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
5
Configurations and components
This PCB can be configured to become a wide range of Tubescreamers. The components needed to
build these configurations can be found in the separate configuration sheet.
If you are not sure which type of components you need to buy, you can follow this list:
1. All resistors are metal film 1% 0,6W
2. Capacitors smaller than 1nF are MLCC unless stated otherwise in the sheet.
3. Capacitors 1nF –1uF are MKT/Wima/SMF which ever you prefer unless stated otherwise in
the sheet.
4. Capacitors 1u and bigger are Electrolytic and rated 25V+ unless stated otherwise in the
sheet.
5. SW1 and SW4 (buffers) can best be miniature PCB mounted DPDT (on-on) switches :
6. SW2 (onboard diode selection) is normally a DIP 2. If the sheet says “jump” you need to short
both poles like this:
7. SW3 (Boost) is a standard DPDT On-On footswitch
8. SW5 (External Diode section)can best be DPDT (On-Off-On). You can find all types of diode
configurations in the diode section of these instructions. You can also buy a separate
clipping PCB in the shop!!
9. SW6 (feedback loop) is a DP3T On-Off-On switch and uses a 220nF and 2nF capacitor on each
side. You will also need to put a 47k in R22 on the PCB. The switch can be wired like this:
Pots
P1 Bass
P2 Gain
P3 Boost
P4 Boost Tone
P5 Treble
P6 Tone (or Glass)
P7 Level

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
6
Build sequence
Before starting with this section, make sure you have read the configurations section first!
Soldering this board can be very complicated for some people since the solder pads are very close
together. Use a magnifying glass to make the job easier.
The trick to soldering a PCB is to work from small to big components. My building sequence
suggestions in this section are based on the parts I used myself. Sometimes some components are
smaller (or bigger) so always use your own common sense and change the order accordingly. Usually
capacitors can differ a lot in size depending on their rating and value.
Note: Do not blow on your solder in an attempt to cool it down. That can result in a bad join that
might corrode! Also take extra care not to short components.
Start by soldering the jumpers, resistors and small diodes (not LEDs if used). If needed you can create
a jumper using a spare piece of lead from a resistor or diode.
If you want to experiment with other transistors for Q1 and Q2 then you could socket them instead
of soldering them to the board. You’ll need a some 20 SIL sockets, break off the 3 pin sockets and
solder them to the board. Now is the time to solder the socket for the IC. Place the transistors and IC
once you are finished with all soldering and off board wiring!
Now continue by soldering the MLCC, small SMF/MKT/Wima capacitors. Now finish by soldering the
transistors (if not socketed), the bigger SMF/MKT/WIMA and the electrolytic capacitors.
I suggest you now drill the holes in your enclosure so you can use it during the off board wiring. This
PCB is very sensitive to noise! Prevent crossing input and output wires and keep the wires as short as
possible (and/or use shielding on the input and output).
Besides the components mentioned in the configuration sheet, you will need:
•1 stereo input jack and 1 mono output jack.
•2,1mm DC jack (isolated).
•22 gage stranded hook-up wire.
•LED holder. This enables you to mount the LEDs in the enclosure.
•Footswitch 3PDT (9 pins) and also a DPDT if you are going to build the Boost switch (SW3)
•Hammond 1590B/125B style case (or similar) in your favorite color. If you are going to use
all the switches and pots, I suggest you use a 1590BB enclosure.

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
7
Off board wiring
Potentiometers
In the pictures below you see the correct pin numbering of the pots (Alpha 16mm style).
Solder the wires accordingly and it is always a good idea to twist the wires together to create some
extra shielding against external noise. The rectangle pad marks pin 1.
You can break off the pin I marked with the yellow circle with a small pair of pliers.
Main bypass wiring
Ring
Sleeve
Tip
Cathode (short leg)
Input
Anode (long leg)
Tip
Sleeve
Output
Rled
3 2 1

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
8
Rled can be somewhere between 1k5 and 10k (try 4k7). The lower the value the brighter the LED
shines, but at the cost of power consumption and wear of the LED.
The diagram is also based on star wiring where all ground connections go to the sleeve of the input
jack. It requires very good conductivity between the input jack, output jack and the enclosure to
work correct. If you do not have good conductivity, please connect a wire between the input jack
sleeve and the output jack sleeve.
Boost wiring Tim™(optional)
You could also use a DPDT footswitch
Effects loop wiring Tim™ (optional)
Anode (long leg)
Cathode (short leg)
R led
Return
Tip
S
M
Sleeve
Tip
Switch
Sleeve
Send

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
9
External Diodes configuration
The wiring for the SW5 switch is the same as for potentiometers, marking pin 1 with a rectangle pad.
There is no wrong way to wire it as long as the middle lugs of the DP3T are connected to one of the
pads like this:
The optional diode switch (SW5) enables you to switch between 2 sets of diodes. There are so many
combinations possible and that is why there is a whole page committed to all kinds of combinations.
Feel free to experiment and combine all kinds of diodes.
If you want to use both the onboard as well as the off board diode combinations then make sure you
add SW2 (DIP2) to the PCB so you can switch off the onboard diodes when you wish (like the Tim™).

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
10

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
11
Modifications
OpAmp
Almost all types of dual OpAmps can be used as long as the pinout is the same. Just a few that have
been tested with success (meaning, they sound good). JRC4558(P), JRC4559, OPA2134, TL072, TL082,
JRC 1458, AD712, OPA2604.
Transistors
The buffer transistors can als be 2N3904 or 2N5088. These transistors do have a different pinout
than the 2SC1815. Extra pads added have been added to the PCB to accommodate these pinouts.
Check the pinout of your transistor before you insert then in the corresponding B/C/ or E pad.
Troubleshooting
All PCB’s have been 100% factory e-tested and out of every batch I receive I build an effect to double
check, so there should not be a connection problem on the PCB itself.
The board is not working (at all), what now?
•Check if your 9V is plugged in correctly (and/or soldered correctly on the board). Pay special
attention to the polarity.
•Check that you oriented the capacitors, IC’s ,transistors and diodes the right way. SMF, MKT
and ceramic capacitors as well as resistors do not need to be oriented. A likely sign of
incorrect capacitors and/or orientation is when an effect is sputtering, rumbling or
“motorboating”.
•Check if you used the correct values of the components. For resistors you can look here:
http://www.diyaudioandvideo.com/Electronics/Color/
•Double and triple check your soldering! A loose or cold solder can be really bad for your
board.
•Replace the IC and/or transistors, one might be defective. Before doing that first unplug the
9V and wait for 5 seconds.
•Check that you have good/high grade components. A lot of Chinese sourced parts are fakes
(especially high end opamps, audio capacitors, vintage diodes and transistors) so be careful
that you source your parts from reliable suppliers.

OmniScreamer v1.0
Manufacturers and product names are mentioned solely for circuit identification, and where applicable their trademarks are the
property of their respective owners who are in no way associated or affiliated with the author. No cooperation or endorsement
is implied.
12
Schematic