JFT 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 JFT Assembly Guide

Thank you for purchasing a JFT Class A Transistor Colour Kit!

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

Place Connectors

jfet-01-connector

Insert Stand Offs and Connector

Begin by snapping in the white nylon standoffs. Make sure you are inserting the the flat side into the Colour PCB. You should feel it snap in. Note that the other side is more rounded, which goes into the Pallet Motherboard for easy inserting and removing. In order to keep the connector in place and level, snap in the stand offs before soldering.
jfet-02-soldering-connector

Solder Connector

Solder the 8-pin connector with the short leads facing up.

Place Resistors

jfet-03-bend-resistor-leads

Insert and Bend Resistor Leads

Bend the resistors and put them into the spaces shown on the PCB legend. Flip the PCB over and bend them against the PCB to keep them in place for easy soldering.
jfet-04-solder-resistor-leads

Solder Resistors

Make sure to keep your tip clean and apply a small amount of solder while placing the tip where the bent lead meets the pad.
jfet-05-trim-resistor-leads

Trim Resistor Leads

Let the freshly soldered resistors sit for a few seconds to cool completely. Then trim the excess leads at the tip of the solder joints.

Place Larger Components

jfet-06-socket-transistor

Capacitors, Transistor and IC Socket

Note that the first revision of PCBs contains an error on the PCB legend: C1's actual value should be .1uF instead of 10uF. Repeat the same process as the resistors for the capacitors. Once all they are bent and held into place, insert the 8-pin IC socket into position, making sure to align the notch in the plastic with the notch on the PCB. Optionally, tape the socket to the PCB to keep it in place when you flip the board for soldering. Insert the transistor with the flat side facing the same way as noted on the PCB and bend the leads. Solder then trim the leads of the capacitors, socket, and transistor. Note: Due to a momentary lapse of reason, we did not install RLED during the making of this guide. That's a mistake. You should install it with all the other resistors.
jfet-07-trim-pots

Trim Potentiometers

Note that, although they look almost identical, there are two different values of trim pots. VR1 is marked "301" and VR2 is marked "103."
jfet-08-Electrolydic

Electrolytic Capacitor

Insert the tall, electrolytic capacitor. This capacitor is non-polarized, so there is no correct orientation for it on the board. Bend, solder, and trim the leads. And that's all for the assembly!
ic-orientation

Insert IC

Insert the IC into the socket. The TL071 IC's orientation is indicated by a circle next to pin one. Insert the IC with the circle facing the notch in the socket and PCB legend.

Calibrate and Check

Distortion and Gain Adjustments

Don't Panic: The steps below require you to adjust a component on the JFT board while the circuit is powered up and working. If you accidentally touch the wrong components with the screw driver, it may damage your JFT, Palette, or even 500-series rack. Take a deep breath, keep a steady hand, and enjoy the experience. This is real DIY, my friend!

No two of the transistors used in the JFT are exactly alike. So to make them behave the way we want, we've got to adjust their surrounding environment a bit. This requires a screw driver, audio interface, and the most sophisticated test equipment known to humankind: your ears.

Plug your assembled JFT into your assembled and tested Palette, turn it on, and connect it to your mixing setup so that you can send signals to your Colour and monitor its output. Send some typical program material to your Colour channel--acoustic guitar and piano tracks work well, but you will surely want to try various sources. Simply assign the track to the output your Colour is plugged into and set the track's fader at its default level. If your interface includes a volume control for the line outputs, set the control to unity gain, sometimes marked as "line" or "+4dBu."

Now play with the front panel controls and the JFT's distortion trim until it sounds like the tool you want it to be. What we're going for here is to set the JFT trim where the unit is most useful and inspiring to you for a range of program materials and Colour settings. Your ears will make the final decision, but here are some general guidelines:

  • With the Colour control turned all the way down, distortion should be practically unnoticeable.
  • With Colour turned all the way up, distortion should be clearly audible, if not crunchy and agressive.
  • With Colour set to the longer line that leads to the LED on the front panel, distortion should register as an "enhancement" of the original signal. That is, it it heard as "warmth" or "color" rather than distortion.

You will most likely need to go back and forth between the gain and distortion trimmers several times before finding the sweet spot. For the final gain trim, turn the Saturation down all the way and push the JFT bypass/engage switch every few seconds. Adjust the trim until you do not hear a difference in volume between having the JFT engaged and bypassed.

Final Checks

  • Trim pot positions: Is the trimmer marked "301" in the VR1 position and the one marked "103" in the VR2 position?
  • IC orientation: Does the dot on the IC align with the notches on the PCB and socket?
  • Transistor orientation: Does the shape of Q1 match the outline on the PCB?
  • Resistors: Do all of the resistor positions correspond to the component 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?

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.

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