Joranalogue TEST 3 Manual

TEST 3
EURORACK V/mA
METER
1
INTRODUCTION
Test 3 is a purpose-designed tool for measuring
voltages and currents in your Eurorack system.
This means that just a single circuit board or
module can now replace a convoluted test setup
with multiple multimeters, custom cables etc.
Two push buttons allow you to cycle the value
shown on the LED display between three
measurements (voltage, current and stored peak
current) of the three power rails. The peak
currents continually update in the background
on all rails, making it ideal for quickly getting
maximum current figures.
Apart from measuring the current draw of a
single module, Test 3 also supports testing power
supplies and cables, measuring an entire system
(up to 1 A of current on each rail), troubleshooting
DIY modules, powering a skiff or breadboard
from a larger system...
BUILD INSTRUCTIONS
Test 3 is available as a Do-It-Yourself (‘DIY’) Kit
with an optional Front Panel Kit.
For detailed build instructions, scan the QR code
below with your mobile device or visit this URL:
https://joranalogue.com/test3/build
The Build Instructions document also lists the
package contents for both the DIY Kit and Front
Panel Kit.

TEST 3
EURORACK V/mA
METER
2
CONTROLS & CONNECTIONS
1 LED DISPLAY
The selected measurement of the selected
power rail is shown on the LED display.
If the measurement goes above the limit, the
display will blink to indicate an overload
condition.
2 RAIL LEDS
The LED of the currently selected power rail (+5,
+12 or −12) lights up.
3 RAIL BUTTON
Press the rail button to cycle through the power
rails.
4 MODE LEDS
The LED of the currently selected measurement
(voltage in volts or current in milli-amps) lights
up. The mA peak LED flashes briefly if a new peak
current value is reached on one of the rails, and
stays lit continually when in peak mode.
5 MODE BUTTON
Press the mode button to cycle through the
measurement modes.
If this button is held down, the mode will switch
to mA peak and the display will blink. Release
the button to reset all stored mA peak values to
0, or press the rail button to cancel.
6 METER OUTPUT HEADER
Connect a module to this output socket via a
standard Eurorack power cable to measure its
current draw. Using a ‘flying busboard’ power
distribution cable, multiple modules can be
connected as well (up to 1 A of current per rail).
The power rails are protected against reverse
voltage, but not against large continuous
overloads!

TEST 3
EURORACK V/mA
METER
3
HOW TO USE
VOLTAGE (V)
Eurorack modules are powered from three DC voltage rails: +5 V, +12 V, and −12 V. Not all modules use all
three rails. The +5 rail is considered optional: it is meant to power digital circuitry, and not all power
supplies deliver it.
Test 3 allows you to check the voltage rails of a power supply. Simply set it to V mode, and cycle through
the rails using the rail button. The measured voltages should be within about 10 % of their nominal values.
If a power supply is overloaded, the voltages on one or more rails will start to drop, until eventually the
overcurrent protection engages and one or more rails are switched off. If only one rail goes out, this can
damage some modules. Test 3 allows you to monitor the rails, so you can switch off an overloaded system
before damage occurs.
CURRENT (mA)
The current draw of Eurorack modules can vary greatly. Analogue modules tend to draw constant
currents, changing slightly with knob settings. Digital modules often have irregular current draws,
changing greatly depending on the selected operation mode. LEDs and displays also have a large impact
on the current draw.
It’s important to determine the maximum current draws of a module on the different rails. The Eurorack
system’s power supply should have enough capacity to source these currents, at all times. These are the
figures that should be published, not the ‘typical’ values! Once the maximum current draws of all modules
in a system are known, calculating the current draws of the entire system is simply a matter of adding up
the figures of the separate rails.
In the regular mA mode, Test 3 will show the real-time current draw. Whenever a maximum value is
reached, it is stored to the mA peak. To measure a module’s maximum current draws, power it from the
Test 3 meter output header and use it in various ways: try different knob settings, patch inputs and
outputs, and make as many LEDs light up as possible. Once you’re done, use the mode button to enter
the mA peak mode, and write down the values of the different rails.
Modules will often draw a large current spike when powered up. A power supply should be able to handle
these short spikes, which can also vary greatly, so you typically don’t need to measure these. It’s
recommended to reset the mA peak measurements (by holding down the mode button) after plugging
in a module. This removes the start-up measurements, allowing you to get the maximum current draws
during actual use.
If you are building your own DIY modules, Test 3 can be a very useful troubleshooting tool. After building
a module, first check if there aren’t any short-circuits on the power lines using a standard multimeter.
Then power it from Test 3 and monitor the current draw(s). If these figures are wildly different from the
expected values, this indicates that there’s an issue with the module.
Test 3 is also an excellent aid during Eurorack module development. Use it to power breadboards and
prototypes, and track how the module’s current draws change as the design progresses. As design
problems often cause excessive current draws, this can speed up the development cycle.

TEST 3
EURORACK V/mA
METER
4
SPECIFICATIONS
FORMAT
Doepfer A-100 ‘Eurorack’ compatible module
3 U, 8 HP, 28 mm deep (inc. power cable)
Also available as semi-assembled circuit board,
without front panel.
MEASUREMENTS
V: 20 mV resolution, 20 V maximum,
±5 % accuracy, updates at 10 Hz
mA: 1 mA resolution, 1 A maximum,
±5 % accuracy, updates at 10 Hz
mA peak: updates at 100 Hz on all rails
simultaneously
BURDEN VOLTAGE
50 µV/mA
MAXIMUM CURRENT DRAW
+12 V: 35 mA
Test 3 draws all current needed for its operation
from the +12 rail. This current is not added to the
mA measurement of the +12 rail. Negligible
current (< 1 mA) is drawn from the +5 and −12
rails if these are available. At least 7 V is required
on the +12 rail for Test 3 to power up and
function properly.
POWER PROTECTION
Reverse polarity (MOSFET)
OUTER DIMENSIONS (H X W X D)
104 x 39 x 11.5 mm (circuit board)
128.5 x 40.3 x 24 mm (module)
MASS
Without front panel: 30 g
With front panel (module): 60 g
DIY Kit: 50 g
Front Panel Kit: 45 g
SUPPORT
As all Joranalogue Audio Design products, Test 3
is designed, manufactured and tested with the
highest standards, to provide the performance
and reliability music professionals expect.
In case your Test 3 isn’t functioning as it should,
make sure to check if you have followed the
Build Instructions exactly. Also check your
Eurorack power supply and all connections.
If the problem persists, contact your dealer or
send an email to [e-mail].
Please mention your serial number, which can be
found on the circuit board’s rear side.
REVISION HISTORY
Revision B: initial release.

With compliments to the following fine people,
who helped to make Test 3 a reality!
Björn Jauss Boris Uytterhaegen
Eric Lukac-Kuruc François Gaspard
Ģirts Ozoliņš Gregory Delabelle
Jan D’Hooghe Jens Van Daele
Everyone at Wired Electronics
Test 3 User Manual
version 2023-06-26
© 2017—2023
[e-mail]
https://joranalogue.com/
Designed & made in Belgium