Lynn Electronics CTR2-Mini+ User manual

CTR2-Mini+ Assembly Manual
Version 1.1 Page 1
CTR2-Mini+ Assembly
Manual
Version 1.1
November 18, 2022

CTR2-Mini+ Assembly Manual
Version 1.1 Page 2
Contents
Introduction ..................................................................................................................................................3
Tools You Will Need......................................................................................................................................4
Bill Of Material (BOM)...................................................................................................................................4
PCB Kit...........................................................................................................................................................5
Pre-Cut Enclosure..........................................................................................................................................5
Cutting your Own Enclosure .........................................................................................................................6
Drill Mounting Holes .................................................................................................................................6
Interconnect Ribbon Cable ...........................................................................................................................8
Installing the Components............................................................................................................................9
Base PCB Assembly .......................................................................................................................................9
16-Pin Ribbon Connector –J3.............................................................................................................10
Jacks....................................................................................................................................................10
Dual-Row 8-Pin Header.......................................................................................................................11
Internal or External Radio I/O.............................................................................................................11
Isolated PTT and Key Output Relays...................................................................................................12
Front Panel PCB Assembly ..........................................................................................................................12
GPIO Connector ..................................................................................................................................12
16-Pin Ribbon Connector –J1.............................................................................................................13
Installing the Controls.............................................................................................................................13
Headphone Jack, J4.............................................................................................................................14
Volume Control...................................................................................................................................16
Encoder...............................................................................................................................................17
Pushbuttons........................................................................................................................................18
Speaker ...............................................................................................................................................19
Assembly.....................................................................................................................................................19
Quick Start Guide........................................................................................................................................21
Appendix A - Schematics.............................................................................................................................23
Appendix B –Top Section Grubbing Template...........................................................................................25
Appendix C –Radio Wiring Diagrams .........................................................................................................26

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Introduction
CTR2-Mini+ is an expanded version of CTR2-Mini. Like CTR2-Mini, the CTR2-Mini+ is a small radio
controller based on the Wio Terminal from Seeed Studios. The Wio contains the processor, a 2.4” color
LCD display, three user buttons, a 5-way switch, a micro-SD slot, and a 40-pin GPIO bus. The GPIO bus is
compatible with many Raspberry Pi accessories.
CTR2-Mini+, herein referred to as the Mini+, shares the same DNA as the Mini. It is named Mini+
because of the extras included that are not standard or available on the Mini. These include:
A built-in function keypad
A built-in radio I/O circuit that eliminates the external Radio I/O module used on the Mini if you
are only controlling one radio. The Mini+ still supports the RJ45/CAT5 connection to a manual
RJ45 switch and external Radio I/O modules if you have two or more radios you wish to control.
A built-in 12 volt power supply that allows you to power the Mini+ from your station’s 12 volt
system or from the USB-C connector on the bottom of the Wio Terminal.
A new sidetone amplifier with built-in volume control with On/Off switch
Several different enclosure options including the PacTec KEU-5 shown in the lead photo, a
custom acrylic enclosure similar to the Mini, and panel mount.
The basic layout of the Mini+ is similar to the Mini. The photo below shows the Mini+ connected to an
FTdx101. The straight key and PC are optional.
Basic Mini System

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As we’ll see in this manual, the Mini+ only requires two circuit boards (and a back panel board) so it is
easier to build and slightly less expensive to construct if you are controlling a single radio.
The Mini+ is available as a bare PCB kit (with SMT components installed and mounting hardware
included). I’ve created a Bill-of-Material (BOM) on Mouser.com for you to order the necessary
components with just a few clicks. It is also available as a complete, fully assembled unit complete with
an updated and pre-programmed Wio Terminal through my blog, https://ctr2.lynovation.com
Tools You Will Need
This manual assumes you will be installing the Mini+ in the PacTec KEU-5 enclosure. To build this kit you
will need basic hand tools like a Phillips screwdriver, diagonal cutters, needle nose pliers, a small wrench
to tighten the nuts on the control shafts, and a temperature controlled soldering iron. I prefer a beveled
tip but you can use what you like. You’ll also need a coping saw or a Dremel tool to grub out the top of
the KEU-5 enclosure so the front panel PCB will mount flush with the top. You’ll also need solder and
possibly solder braid if you create any solder bridges. The boards are manufactured using leaded solder
so consider that before purchasing.
Bill Of Material (BOM)
As mentioned above, I’ve created a BOM on Mouser.com that includes everything you’ll need to build
the Mini+, except the boards. I can supply the boards for a minimal cost. The link to the Mouser BOM is
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=22e0705943

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PCB Kit
The Mini+ PCB Kit consists of two PCBs, a back panel, and mounting hardware. All the SMT components
are preinstalled at the PCB factory. You only need to install the through-hole components and build a
ribbon cable. The front panel, shown on the left in the photo below, mounts flushes in the recess in the
KEU-5 enclosure. The base board, shown on the top-right mounts in the lower half of the enclosure. The
PCB kit includes the back panel board and the mounting hardware as shown below.
Pre-Cut Enclosure
I can supply a CNC cut PacTec KEU-5 enclosure if you don’t want to cut your own. If you purchase an
enclosure from me be sure to delete it from your Mouser order.
You can order PCB and the pre-cut enclosure on the order form on my blog.
Printed Circuit Board Kit with Mounting Hardware
Pre-cut PacTec KEU-5 Enclosure

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Cutting your Own Enclosure
If you choose to purchase the KEU-5 enclosure from the Mouser BOM you’ll need to prepare it for
mounting the circuit boards.
Drill Mounting Holes
The first task is to drill the
mounting holes in the
bottom and top sections of
the KEU-5 enclosure. Take
the Base PCB and lay it
bottom up (with the ICs on
top) in the bottom half of
the enclosure as shown in
the photo to the right. The
concave notches on the
board should fit next to the
original mounting bosses in
the box.
Insert the enclosure’s back panel in the slot on the back of the bottom half and push the PCB toward the
back panel until it touches it. This is where the base PCB is to be mounted. A piece of tape will help hold
it in place. Drill 1/8” holes into the enclosure bottom at the four mounting holes on the PCB. The base
will mount to these holes using M3-6mm standoffs supplied with the PCB kit.
CAUTION: Be careful when drilling these holes so that the drill bit doesn’t cut into the through-hole
plating on the board’s mounting pads.
Next, lay the blank front
panel PCB face-down
(IC-1 on top) in the
recess on the top
section of the enclosure
as shown here. Drill a
1/8” hole at each
corner mounting pad.
NOTE: Drill these holes
before grubbing out the
center so you can leave
plenty of material
around the holes for
the mounting screws.
Drilling Front Panel PCB Mounting Holes
Drilling the base board’s mounting holes

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Next, print out the template in Appendix B and cut it out. Lay it in the recess in the top panel and mark
the cut lines as shown the left photo below. Use a fine-tooth coping saw or a Dremel tool to grub out
the inside of the recess. It doesn’t have to be pretty. Just make sure you leave about 1/8” of the
recessed portion for the board to sit on and be sure to leave flanges in each corner where the mounting
holes are located. Once complete the top section should look like the photo on the right. The front panel
PCB should fit into this void.
NOTE: The notch for the encoder is on the bottom (narrow end) of the top section of the enclosure.
Grub Template
Grubbing Complete

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Interconnect Ribbon Cable
A 60mm 16-conductor ribbon cable connects the front panel PCB to the base PCB. To build this cable,
cut an 80mm length of 16-conductor ribbon cable then install the ribbon cable connectors on each end
as shown below. The finish length after the strain-reliefs are installed should be around 60mm. You can
build this cable longer if you want more space between the board when you assemble or disassemble
the enclosure but I find 60mm to be about right.
NOTE: When building the cable, make sure that the #1 pin of both connectors is on the same conductor
(indicated by the red stripe). The #1 pin is marked by a small triangle on side of the connector as shown
in the photo on the left. When the connectors are properly installed the cable should look like the cable
in the photo on the right with the key for each connector facing toward the ribbon cable.
When building the ribbon cable be very careful that you cut the ends square. I use a ruler as a straight-
edge. Hold the cable under it flush to the upper edge then use a pair of sharp scissors to cut the end
square as shown in the photo below.
Pin 1 Marker
Finished ribbon cable
Cutting the ribbon cable

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Installing the Components
I find it’s much easier to install components if the board is installed in a PCB vise. Working with the
bottom of the board facing up I insert each connector into its holes from under the board. I hold the
solder with my left thumb and index finger and use my left middle finger to hold the connector in
position. Once I have soldered one or two pins, I remove the board and check to make sure the
connector is positioned properly and laying flat against the board. It’s easy to reposition it with only a
couple of the pins soldered. Once I’m happy with its placement I solder the rest of the pins. You’ll see
me using this technique throughout this manual.
Base PCB Assembly
The base PCB is the easiest to build. All the components are through-hole and mount to the top of the
board. There are silkscreen outlines for each component.
A WORD OF CAUTION
If you use a PCB vise like I do be extremely careful when installing the base PCB into the vice. There’s a
row of SMT resistors and capacitors next to the ULN2803A Darlington driver chip on the bottom of the
board. If your vice has slots to hold the PCB it may break these components when you tighten it. I
recommend clamping the board as shown in the photo below to eliminate this problem.
Watch out for these components!

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16-Pin Ribbon Connector –J3
Let’s start by installing J3, the 16-pin ribbon cable connector. As shown in the photo below this
connector mounts on the top of the PCB and the pins face backwards toward the connectors on the rear
of the board. Place it in position then use one finger to hold it to the board while you solder it. While it is
hard to do, be careful that you don’t form solder bridges between the pins. If you do, use some copper
braid (SolderWick or equivalent) to remove the bridge.
Jacks
Next, mount the RJ45 jack, the four 1/8”
stereo jacks, and the barrel connector for
the power.
When mounting these jacks, place your
finger on the jack to hold it in place and
gently pull the jack toward the rear edge of
the board. The pins on the jack should
touch the rear edge of the holes they’re in,
as shown the photo at the left. This will
insure that the jacks are all lined up across
the back of the board and their barrels
extend past the back edge of the rear panel.
Make sure the power connector is square to the board. Once it’s soldered in it is very difficult to
reposition.
Be very careful when soldering the pins on the RJ45 jack. They are close together and you can easily
form solder bridges between them. Also, don’t forget to solder the four leads for the LEDs on this
connector.
Installing J3
Install connector with pins close to the edge

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Once you’re done the board should look like the photo below. You’ll want to use some flux remover to
clean off the flux.
Jacks installed
Dual-Row 8-Pin Header
The final task of populating the
base PCB is to install the dual-
row 8-pin header for the
internal radio I/O circuit. The
photo to the right shows the
completed base PCB with
jumpers installed on the 8-pin
header.
Internal or External Radio I/O
The Mini+ has an internal radio I/O circuit. If you don’t plan on using the internal radio I/O circuit (i.e.
you’re going to use the external Radio I/O module instead) you don’t need to install the dual-row 8 pin
header or J1 and J6, the CAT I/O and PTT/Key Out 1/8” jacks.
Conversely, if you’re not planning on using external Radio I/O modules you don’t need to install J4, the
RJ45 jack.
I recommend you install all of the jacks so you have flexibility in the future. When using the internal
radio I/O circuit install the appropriate jumpers on the dual-row 8-pin header. When using the external
radio I/O module, remove all of the internal jumpers. I place each one of them on a single pin for storage
so I have them when needed again.
Completed base PCB

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Isolated PTT and Key Output Relays
If your radio is older and uses keying voltage greater than +50 volts, or uses negative voltage for grid-
block keying you will need to install the PTT/Key Relay modification. This modification adds two reed
relays to the Mini+ that allows you to key radios using voltages up to +/- 200 volts.
This modification requires you to cut JP1 and JP2 on the top of the board, install the reed relays on top,
and add flyback diodes D3 and D4 on the bottom of the board.
You can order the relays and diodes from Mouser using this BOM.
Front Panel PCB Assembly
The front panel uses a fairly unique construction technique that results in a professional looking control
panel at a very inexpensive cost. The PCB is actually the front panel. While this is not unique, many kit
manufacturers do this, the method of mounting and connecting the controls from the front panel to the
Base PCB is uncommon. I’ve written an article for QEX describing the method of creating the PCB for the
front panel. It’s scheduled for publication in the January/February 2023 issue.
All of the controls mount on the bottom of the front panel PCB and connect to the board using short
jumper wires landing on large pads near each control. These pads route the control signals to J1, the 16-
pin ribbon connector. A 16-conductor ribbon cable connects to J3 on the base PCB. This technique
greatly simplifies and declutters the Mini+ assembly.
GPIO Connector
The good news about this connector is that you don’t have to install it! In order to have the Wio
Terminal mount as low as possible on the front panel the dual-row 20-pin header must be slightly
modified, installed, and then the plastic retainer needs to be removed. I found this was probably more
difficult that a typical build would want to do so I install these headers on all PCB kits. I also glue a
couple of M3 washers on the M2 holes on the front panel for the Wio Terminal to rest on so the PCB
doesn’t warp when these screw are tightened.

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16-Pin Ribbon Connector –J1
The first
connector you
should install
is J1, the 16-
pin header
connector. It
mounts on the
bottom of the
board as
shown here.
Solder it from
the top side of
the board.
Once completed, trim the
leads protruding on top
with flush-cutters so the
Wio Terminal doesn’t rest
on them.
Installing the Controls
The next step in assembling the front panel is mounting the controls. Everything mounts on the bottom
of the board.
NOTE: Install the speaker after all other controls have been mounted and the flux removed. The flux
solvent will melt the foam pad use to stick the speaker to the board.
Before you start installing controls, add a blob of solder to every pad except the center pad on the
headphone jack as shown in the next photo. Don’t hold the soldering iron on the pad too long or you’ll
burn all the rosin off. You’ll be tacking wires to these pads so a little extra rosin helps.
I use 26 gauge solid copper wire from indoor CAT5 wiring cable to make the connections from the
controls to the board. I strip the insulation from the wire since it’s not needed in this application. If you
use stranded wire, tin the ends before soldering them.
J1 installed next to IC1
Flush cut J1’s pins on top

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Add a solder blob to each pad before installing components
Headphone Jack, J4
Mount the headphone jack next.
Add a slight bend to the center terminal on the barrel
end to bring it down to the board before tightening it
down. It should touch the pad when you tighten the
mounting nut. It helps if you don’t add a blob of solder
to this pad as noted above.
Solder the center terminal to the pad on the PCB as
shown in the photo to the right.
Headphone jack installation

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Next, take a short length of wire and put a 1/16” bend
on one end to form a hook. This end will be set into the
solder blob.
Insert this wire through the top-center terminal and melt the
hook into the solder blob on the right hand pad as shown in
the photo on the right. Just heat the pad with your soldering
iron and push the wire into the blob. This will hold the wire in
place while you solder the other end of the wire to the top-
center terminal.
Next, solder the wire to the top-center terminal and clip it off
as shown here. Go back and touch-up the solder blob on the
pad to make sure the hook end of the wire is completely
covered in solder. A slight curve in the wire acts as a strain
relief.
Next, add a wire to the terminal on the top-left side using the same
technique.
Make sure all connections are solid and that solder flows onto both
the terminal and the wire.
Jumper installed
Headphone jack completed

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Volume Control
The volume control is a little harder to
connect because it just has small pins
without holes.
Start by mounting the control to the bottom
of the board. The anti-twist tab should drop
into the small hole drilled partially through
the PCB. This hole can be seen in the photo
to the right just below the center pin. This
keeps the control from rotating when you
reach the stops.
NOTE: You may need to trim off a small
amount of the tab for the pot to sit flush to
the board.
Start with the center pin. Solder the hook into the
solder blob then clip the wire slightly above the
center pin. Use a pair of needle nose pliers to bend
another small hook on the top of the wire. This hook
should be touching the center pin on the pot as
shown in the photo to the left.
Solder the hook to the center pin of the pot. Be
careful because this wire is short and has a tendency
to melt the solder on the pad too.
Add jumpers using the same technique to the
other four pads for the volume control. When
you’re finished the volume control should the
photo on the right.
Volume control installation
Center pin jumper
Completed volume control wiring

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Encoder
Mount the encoder so the pins align with the pads on
the board and tighten its mounting nut. There is no
anti-rotation tab on the encoder (since it has no
stops).
Solder the two ground lugs to the board. Use a hook
wire to solder the top lug to the pad as shown in
photo to the right. Solder the case of the encoder
directly to the lower pad as shown in the next photo.
To solder the pins on the encoder, solder a hook wire
to the solder blob on the board then bring it up next
to the pin. Make a slight twist around the pin as
shown in the photo to the right. Solder the wire to
the pin and cut off the excess wire then touch up the
solder on the pad. Do this on all 5 pins on the
encoder.
NOTE: Make sure the wires don’t touch each other!
When you’re done the encoder should look like photo
on the left.
Encoder wiring
Finished encoder wiring

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Pushbuttons
Install the pushbuttons last. Mount them to the bottom of the PCB. I put
the washers on top, under the nut so I don’t scratch the panel when
tightening the nuts. I like colored buttons but you can use any color you
want. I recommend using a red pushbutton for PTT (SW6).
Align the nuts on the buttons so they are symmetrical as shown in photo to
the right. It’s OK if the terminals on the back are slightly out of alignment
with the pads.
Before adding wires
Wiring completed 
Installed pushbuttons
Before wiring jumpers
After wiring jumpers

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Speaker
The speaker should be installed after you have
installed all the other components and cleaned the
rosin off the board. The solvent will melt the foam
and glue that attaches the speaker to the board.
To install the speaker remove the paper on the
speaker’s face and stick the speaker down to the
back of the PCB using the silkscreened oval as your
guide. Cut the connector off the speaker wires
leaving enough wire to reach the pads on the
board. Tin the ends of the black and red wire and
solder them to the –and + pads. The photo on the
right shows the completed speaker connections.
Assembly
To assemble the unit simply install the front panel in the recess on the top section of the KEU-5
enclosure and secure it with the supplied M3x6mm screws and nuts. It should sit flush with the top of
the enclosure.
Carefully align the dual-row 20 pin header on the top of the front panel with the Wio Terminal’s GPIO
connector and push the two together. Use the supplied M2x5mm screws to secure the Wio to the front
panel.
WARNING: Make sure the M3 washers that I glued to the top panel are still installed. They provide a
stop to support the Wio and keep it from warping the PCB when you tighten the mounting screws.
Insert the M2 screws from the bottom of the PCB and lightly tighten them.
Install the four M3x6mm standoffs on the base
board using the supplied M3 nuts. Place the base
board into the bottom section of the enclosure.
Next, place the back panel over the jacks on the
board and slide it into the groove on the back of
the enclosure. Use the M3x25mm standoffs to
secure the back two mounting holes and place
the rubber boots on the standoffs as shown to
the right. Use the remaining M3x6mm screws to
secure the front mounting holes.
Installed speaker

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Connect the ribbon cable to J3 connector on the base board. Hold the top section over the bottom
section and connect the other end of the ribbon cable to the J1 connector on the front panel. Secure the
two enclosure halves using the provided screws and install the rubber feet (screws and feet are supplied
with the enclosure).
NOTE: Before you button up your Mini+,
decide if you’re going to use the internal
radio I/O circuit or use an external Radio I/O
module. If using the internal circuit, install
the jumpers on the dual-row 8-pin header
to match your radio’s CAT interface polarity.
If you’re going to use a Radio I/O module,
remove all of the jumpers from this header.
(The red jumpers shown in photo 36
configure the internal radio I/O for RS232
operation.)
Your new Mini+ ready to button up!