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TM79 Assembly Guide

Safety Precautions, Warranty, and Disclaimer Improper soldering and handling of electricity can cause serious injury and damage to your property. Read and understand the instructions below before beginning your project. Follow the instructions, build carefully, and use the appropriate tools. Build at your own risk. DIY Recording Equipment, LLC is not responsible for any damage or injury resulting from the assembly or use of your kit. You are the manufacturer of your kit. It is your responsibility to turn this group of parts into a working piece of recording equipment. DIY Recording Equipment, LLC does not guarantee the success of your project and disclaims any Implied Warranty of Merchantability. Please visit the support forum for assembly support.
Damaged or Missing Parts All kits and parts are checked before being shipped to you. If something arrives damaged or if your kit is missing a part, please open a support ticket to inquire about a replacement. Missing parts will be replaced at our expense. Damaged parts should be returned for verification. If the part shows signs of use beyond what was necessary to determine that it was damaged, DIY Recording Equipment, LLC reserves the right not to replace the part.

Welcome to the TM79 Assembly Guide

Thank you for purchasing a TM79 Multi-Stage Saturation Colour!

If this is your first DIY project ever, we recommend reading our Getting Started Guide.

Print this guide

Table of Contents

Required Tools

You'll need the tools below to complete this build.

Soldering Iron
We recommend an adjustable-temperature station, such as the $40 Weller WLC100.

Solder
You can use 60/40 "leaded" solder or lead-free. We recommend 60/40 because it flows better and is easier for beginners to use.

Wire Cutters
You'll need a pair of good "snips" for cutting of the excess leads after soldering.

Optional Tools

These tools aren't strictly necessary but can make your build a bit easier.

Multi-Meter
If you find the color bands on resistors a bit hard to read, you can use a meter to sort them with absolute confidence.

Desoldering Pump
If you accidentally solder something in the wrong place, a desoldering pump can save the day.

0. Resistor Calculator

Type in the value of the resistor you need and this tool will show you the corresponding color code.

Check Revision

This assembly guide is for version 1.0 of the TM79, which was discontinued in 2022. If you bought your kit after 2022, go to the new TM79 assembly guide.

Populate PCB

Sort Components

Before you begin soldering, identify and sort each component using the Component Sorting Sheet (PDF).

Part #	Value	Description	Qty
R2, R3, R6, R14	220k	Resistor, 1/4W, metal-film	4
R7, R9	10k	Resistor, 1/4W, metal-film	2
R10	68R	Resistor, 1/4W, metal-film	1
R4, R5	82R	Resistor, 1/4W, metal-film	2
R12	750R	Resistor, 1/4W, metal-film	1
R11	910R	Resistor, 1/4W, metal-film	1
R13	3k	Resistor, 1/4W, metal-film	1
R8	5.1k	Resistor, 1/4W, metal-film	1
CON1	8-pin	Dual-row header	1
-	Standoff	Nylon, press-fit, 1/8"	4
C7	22p	Capacitor, ceramic	1
C1, C2	.1u	Capacitor, film	2
Q1, Q2	2N7000	Transistor	2
C6	3.3n	Capacitor, film	1
C8	10n	Capacitor, film	1
C5, C9	47u	Capacitor, electrolytic	2
C3, C4	100u	Capacitor, electrolytic	2
U1	CA3240EZ	Opamp, dual	1
T1, T2	TY-250P	Transformer	2

Standoffs and Connector

Press the four standoffs into the mounting holes. The standoffs have two different sides: a locking side with notched tabs and a press-fit side with sloped tabs. Press the locking side into the TM79.

Solder Connector

Now lay the PCB and standoffs on top of the 8-pin connector CON1. Solder the connector to the PCB from the top.

Insert and Bend Resistor Leads

Insert the resistors into their respective places as indicated on the PCB. Bend the leads against the PCB bottom so that the resistors stay in place when you flip the board over for soldering.

Solder and Trim Resistors

Flip the PCB over and solder the resistors to the PCB. Once the solder has cooled, trim the excess leads down to the solder joint.

Populate Remaining Components

Populate the rest of the PCB, progressing from the lowest-profile components to the highest. You may want to split this up into three rounds of components of similar height:

U1 (opamp), C7 (yellow, note that the actual value is "22p" not "33p" as marked on the PCB)
C1, C2, C6, C8 (box capacitors), Q1, Q2 (transistors)
C3, C4, C5, C9 (electrolytic capacitors), T1, T2 (transformers)

Note that the transistors, electrolytic capacitors, and transformers must be installed with a certain orientation. For transistors Q1 and Q2, the orientation is indicated on the PCB by the round and flat sides of the component body. For transformers T1 and T2, orientation is indicated by semi-circular notches on the PCB that match those on the white plastic beneath the transformer's steel laminations. Finally, the polarity of capacitors C3, C4, C5, and C9 is indicated on the PCB by a + and a square pad for the positive lead. The negative lead is indicated on the capacitors themselves by a stripe containing "-" symbols.

Final Checks

Before you wrap up, check the following things:

Capacitor orientation: Is the stripe on the cap on the opposite side from the "+" marking on the PCB?
IC orientation: Does the dot/notch on the IC align with the notches on the socket and PCB?
Transistor orientation: Does the shape of the transistor match the outline on the PCB?
Resistors: Do all of the resistor positions correspond the chart and/or sorting sheet?
Soldering: Is every solder joint shiny and clean? If one is cloudy or misshapen, try reheating it for 8 seconds and adding a tiny bit more solder.
Trimming: Are all of the excess leads trimmed down as close to the joint as possible?

All good? Congrats on finishing your build! Have a question or problem? Drop us a line.