Synthesis Technology MOTM-110 Ring Mod & VCA User manual

MOTM-110 Ring Mod & VCA
Assembly Instructions
Synthesis Technology
6625 Quail Ridge Dr.
Fort Worth, TX 76180
(888) 818-MOTM
www.synthtech.com
June 3, 1999

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MOTM-110 PARTS LIST
Please carefully check that all parts are in your kit. If you have a suspected shortage,
please call or email. If you get free extra stuff, keep it for next time.
Capacitor bag, containing the following 19 parts:
3ea 10mfd, 50V Electrolytic C1, C4, C5
2ea 150pf (151) ceramic axial C2, C3
3ea 0.47mfd (470n) yellow box polycarbonate C6, C7, C8
3ea 0.01mfd (10n) yellow box polycarbonate C9, C10, C11
5ea 0.1mfd (104) ceramic axial C12, C13, C15-17
2ea 22pf ceramic axial C14, C19
1ea 0.001mfd (1n) yellow box polycarbonate C18
Resistor bag, containing the following 27 parts:
6ea 100K 5% (brown, black, yellow) R8, R9, R11, R13, R14, R16
5ea 1K 5% (brown, black, red) R3, R12, R21, R23, R24
3ea 56K 5% (green, blue, orange) R1, R4, R27
2ea 150K 1% (brown, green, black, orange) R2, R7
2ea 470K 5% (yellow, violet, yellow) R6, R25
2ea 200K 5% (red, black, yellow) R10, R22
2ea 300K 5% (orange, black, yellow) R15, R19
1ea 39K 5% (orange, white, orange) R5
1ea 27K 5% (red, violet, orange) R26
1ea 2M2 5% (red, red, green) R17
1ea 6K8 5% (blue, gray, red) R18
1ea 680 ohm 5% (blue, gray, brown) R20
IC bag, containing the following 5 parts:
2ea OP275GP op amp U2, U3
1ea CEM3330 dual VCA U1
2ea 1N4148 signal diode D1, D2
Misc #1 bag, containing the following 9 parts:
2ea Axial ferrite beads (plain, gray things) L1, L2
2ea SPDT toggle switch SW1, SW2
3ea 100K cermet trim pot TP1 - 3
1ea 18pin DIP socket for U1 @U1
1ea MTA-156 power connector JP1
Knobs, 5ea, ALCO PKES90B1/4
Jacks, 6ea Switchcraft 112A

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PAGE 2 MOTM-110 PARTS LIST
Pots, containing the following:
4ea 100K linear, Spectrol 148 VR2 - 5
1ea 100K linear, Bourns 91 (panel mount) VR1
Front panel
Mounting bracket
Wire bag, containing the following 9 wires:
5ea RG-174 coax, 4 1/2 inches
2ea red/black twisted pair
1ea orange/white twisted pair
1ea blue 24ga. wire
Hardware bag, containing:
4ea #8-32 x 3/8 black screws (for mounting module to rack)
4ea #6-32 x 1/2 zinc screws (for attaching pc board to bracket)
4ea ¼ inch aluminum spacers
6ea #6 KEPS nuts (2 for attaching bracket to front panel, 4 for pc board)
3ea small heatshrink tubing
5ea small tie-wraps
Organic Solder
No-clean Solder
PC Board, MOTM-110
Power cable

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GENERAL INFORMATION
Thank you for purchasing the MOTM-110 Ring Mod & VCA kit. If you have any issues
concerning the building or use of the kit, please contact us at [phone] or by email:
[email protected]
This kit should take the average builder between 2 and 3 hours. However, please
remember this is NOT a speed contest, it is an accuracy contest. There is no rule that you
have to complete the entire kit in one session (as long as you wash the flux off!).
Successful kit-building relies on having the proper tools. Here is a list of what you will
need to build and calibrate your MOTM-110.
* Soldering iron, 50W max power
* Needle-nose or chain-nose pliers
* Diagonal cutters
* Wire strippers
* Small, flat screwdriver for adjusting the trimmers
* Allen key set for securing the knobs
* Lead bending tool (optional, but makes the job go much faster)
* DVM or oscilloscope (optional for calibration. Can calibrate by ear)
* Heat gun for heat-shrink tubing (optional, but HIGHLY recommended)
For more information of tools used and suggestions, see the MOTM FAQ at
www.synthtech.com
HOW TO FOLLOW THE DIRECTIONS
Please read the entire instruction before proceeding. There may be valuable information at
the end of the instruction. Each instruction has a check box next to it. After you
complete the instruction, check the box. This way you can keep track of where you are in
the process.
VERIFY THE PARTS LIST
Verify that all of the parts are in the kit as shown on the parts list.
A WORD ON SOLDERING
There are 2 very different types of solder used in the kit. Most of the soldering uses
‘Organic Flux’ solder. This is strictly for use on the pc board, and is NOT to be used
on the front panel wiring!
In order for solder to ‘stick’ to the copper, a chemical called ‘flux’ is embedded in the solder.
The flux leaves a residue on the pc board that should be cleaned with warm water. DO
NOT USE SOAP OR OTHER CLEANSERS. Most of the parts in the kits are ‘waterproof’,
and can be washed in the sink. The flux is OSHA approved for flushing down the drain, so

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don’t worry about that! A soft brush is used to gently scrub the board. We recommend a
‘fingernail brush’, which is about 1” x 2” and be found for about $1.
The other type of solder is called ‘No Clean Flux’, because as the name implies it does not
require washing. This solder is used on wiring the pots, switches, jacks, etc. This solder is
harder to use on the pc board, because even when melted it is not very fluid (about the
consistency of toothpaste). We will use it VERY SPARINGLY on the pc board.
OK, let’s get started on the board!
PART #1: SOLDERING THE RESISTORS
Since there are more resistors than anything else, we will start here. If you do not know
the resistor color code, refer to the parts list. Resistors are not polarity sensitive, but the
board will be easier to debug (and look nicer) if you point the first color band in the same
direction for all the parts. The color code is also in the README FIRST document that
every customer gets with each order.
Find the RESISTOR bag.
Find the MOTM-110 blank pc board. There is a copy (larger than actual size) of the
silkscreen which shows where the parts go at the end of this document. It will be
useful if you locate the part on the print first, put the part in the board, then
‘check off’ the silkscreen. All parts are inserted from the side of the board with the
white silkscreen (the “top” side).
We will stuff the resistors by value to make things easier. The resistors (and other
long-leaded parts) are inserted on 0.4 inch spacings. The important thing is to be
sure that the part is sitting all the way down on the board. Push the leads in the
holes, push the part on the board, and then bend the leads on the bottom outwards
to a 45 degree angle (roughly!). This is called ‘cinching the leads’: keeps the part
from falling out! From the bottom of the board, solder (with the organic flux),
applying heat to the pad for about a half second first, then applying just enough
solder to make a small, flat puddle.
The rule of soldering: don’t use too much, you can always add more! Cut the leads
flush with the top of the solder.
Locate the 56K resistors and solder into R1, R4 & R27.
Locate the 150K 1% (they look different than the others) and solder into R2 & R7.
Locate the 1K resistors and solder into R3, R12, R21, R23 & R24.
Locate the 100K resistors and solder into R8, R9, R11, R13, R14, & R16.

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Locate the 470K resistors and solder into R6 & R25.
Locate the 200K resistors and solder into R10 & R22.
Locate the 2M2 (2.2Meg) resistor and solder into R17.
Locate the 6K8 (6.8K) resistor and solder into R18.
Locate the 300K resistors and solder into R15 & R19.
Locate the 680 ohm resistor and solder into R20.
Locate the 39K resistor and solder into R5.
Locate the 27K resistor and solder into R26.
PART #2: BOARD WASH #1
Verify all the resistors are in the correct position.
Verify all the resistors are flat on the board. Correct if needed.
Wash the board in warm water, gently scrubbing both sides.
Shake the board a couple of time, blot dry with an old towel (the leads will frazzle
the good towel). Let dry about 15 minutes.
PART #3: CAPACITORS
Locate the CAPACITOR bag.
Locate the 150pf axial ceramic caps. They are marked 151. Solder into C2 & C3.
Locate the 22pf axial ceramic caps. They are marked 220. Solder into C14 & C19.
Locate the 0.1mfd axial ceramic caps. Some kits have these pre-cut and bent to the
correct spacing. Solder into C12, C13, C15 - C17.
Locate the 0.001mfd yellow box cap. It is stamped 102 on the top. Solder into C18.
Locate the 0.01mfd yellow box caps. They are stamped 103 . Solder into C9, C10,
C11.

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Locate the 0.47mfd yellow box caps. They are stamped 474. Solder into C6, C7, C8.

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Locate the 10mfd electrolytics. Note that there is a stripe on the NEGATIVE
terminal. The pc board has a + on the POSITIVE terminal. Carefully stick the
capacitors into C1, C4 and C5 with the stripe away from the + pad on the board.
PART #4: MISC STUFF
Almost done with the parts on the pc board! This will finish up the soldering with the
organic flux.
Locate the MISC #1 bag and the IC bag.
Locate the ferrite beads. They are axial parts, gray colored with no markings. These
are non-polar, and are soldered into L1 and L2.
Locate the 18 pin DIP socket. Solder it into the U1 location (CEM3330). There is a
small notch on one end of the socket: this is the ‘PIN #1’ end. Locate U1 on the pc
board. Note that Pin #1 is the square pad, and there is a notch on the silkscreen.
Locate the MTA-156 power connector. Solder into JP1. Note that the connector has
a ‘locking tab’ on one side. This side is the “inside” facing relative to the pc board.
Note the silkscreen symbol for JP1 has a line on one side, indicating this is the side
where the locking tab goes.
Locate the OP275 op amps. Solder into U2 and U3. Note that Pin #1 is the square
pad. Pin #1 is the pin near the very small ‘dot’ in the top of the part. They are not in
sockets.
Locate the 1N4148 signal diodes. These are clear glass axial parts with a black
band around one end. Locate D1 and D2 on the pc board. Notice that the silkscreen
symbol has a distinct band on one end. Insert the banded end (called the cathode)
into the pc board in the correct pad.
PART #5: WASH THE BOARD AGAIN
Verify all the parts are in the correct locations. Check the diodes and C1, C4 & C5
orientation.
Inspect the solder joints. Any solder shorts? Too much solder? Missing joints?
Wash the board under warm water. Scrub gently. Dry.
THIS IS A GOOD STOPPING PLACE TO REST OR PUT THE KIT AWAY UNTIL
LATER.

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You are now finished with the Organic flux solder. All soldering past this point is
using the No-Clean solder. You do not have to wash the board anymore.
PART #6: FINISHING THE PCB
You will now solder in the remains parts on the pcb in preparation for wiring to the front
panel. USE THE NO-CLEAN SOLDER. BE CAREFUL!
Locate the 3 blue trim pots in the MISC #1 bag. Solder into TP1, 2, & 3.
Locate the 4 Spectrol #148 pots (metal shafts). They are all 100K. IMPORTANT:
in order for the pc board to properly align into the front panel, each pot must be
absolutely flat on the pc board, with the shafts pointing away from the pc board.
Solder the pots into VR2 - 5. Clip the leads off.
Locate the WIRE bag. Note that the pre-stripped wires all have a short end and
a longer end. THE SHORT END GOES IN THE PC BOARD.
Locate the white/orange twisted pair. Solder the WHITE wire into JP2, in the hole
marked GND (square pad).
Solder the ORANGE wire short end into JP2, in the CV hole.
Locate one of the red/black twisted pairs. Solder the RED short end into S1,
into the top hole (round).
Solder the BLACK short end into S1, bottom hole (square).
Solder the other red/black twisted pair as before into S2.
Locate the 5 pieces of RG-174 black coax cable. Again, note that one end has
longer wires stripped than the other. The short ends will go in the pc board in
positions J2 to J6. Look at the pc board. Notice that in positions J2 - J6, there
is a large hole pad (lower pad) and a smaller pad (top hole). The braided wire
is soldered into the larger hole. The smaller, inner conductor goes in the top
hole.
Note there is a row of ‘plain’ holes along the bottom, under J2 - 6. These holes are
for threading the small white tie-wraps for holding the coax against the pc board. The
holes are designed so that coax exits the pads from the right side. The coax then lies
in between the 2 holes. The tie wrap enters the left hole from the top, comes out
the right hole from the bottom, and is then secured so that the coax is tightly
held against the top of the pc board. Note that the tie wraps must thread from the
top, or there may not be sufficient room between the pc board and the mounting
bracket. The excess tie wrap is cut off.

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Solder, then tie-wrap the 5 coax cables J2 - J6. Trim the excess tie-wrap. NOTE:
because of the way the coax is made, chances are more of the braid will go in the
hole than the inner conductor. This is normal, unlike all the other parts and
wires. The secret is to get the coax firmly soldered and tied down.
YOU ARE NOW FINISHED WITH THE PC BOARD WORK! BREAK TIME.
PART #7: FRONT PANEL PREPERATION
You will now attach components to the front panel. It is HIGHLY recommended that you
use a set of hollow shaft nut drivers, NOT PLIERS, to tighten the nuts. This prevents
scratching. NOTE: all references to part orientation is from the REAR of the panel.
Locate the 6 Switchcraft jacks. Notice that from the rear, there is a beveled corner.
This corner is ALWAYS CONNECTED TO GROUND, USUALLY WITH THE
BRAIDED CONDUCTOR. Each jack has a flat washer, a lockwasher, and a ½” hex
nut. Remove the nuts and washers from each jack. Place aside. Keep the lockwasher
on the jacks.
Insert the 6 jacks/lockwashers, with the beveled corner in the upper right corner,
into the 6 holes. Place the flat washer on the jack, then the hex nut. Hold the jack
with one hand on the backside, keeping it ‘square’. Tighten the hex nut with a nut
driver. NOTE: when tight, not much of the exposed threads of the jack are exposed.
Check to see that each jack has the bevel in the upper right corner, and all jacks are
neatly lined up.
Locate the 2 SPDT toggle switches. Remove the hex nut (keep the lockwasher on),
stick the switches in the holes labeled AC/DC .Place the hex nut on the switch and
tighten. Be sure the switch is straight up and down: it is easy to get it slightly
off-center.
Locate the 100K Bourns 91 pot. It is blue. Remove the first hex nut, keeping the
lockwasher and second hex nut on the pot. Insert the pot into the upper right hole,
with the 3 leads pointing down towards the jacks.
CAREFULLY, tighten the hex nut, holding the pot with one hand to keep the 3
leads pointing downwards. DO NOT OVERTIGHTEN!
You are now ready to attach the pc board to the bracket, and then wire up to the panel.
See the illustration at the end of the document.