Welcome back to another episode of our Make It Monday series. This week, we will be putting together a Mojotone 5E3 Tweed Deluxe Style Amplifier Kit. This is going to be a longer article, so we will break it up into 3 separate episodes. Part 1 of this 3-part series will illustrate the installation of initial hardware parts onto the chassis, as well as populating and soldering the fiberboard. So let's get started!
Right off the bat, we will unbox our kit to find a wide variety of hardware, electronics, wires, etc. For a deeper look at what's inside the kit box, please refer to the unboxing video below.
So to start, we will need to locate our chassis, our transformers, and all of our basic hardware components (switches, pilot light assembly, tube sockets, jacks, etc.). Once we've done this, we will start by installing all of our potentiometers with their solder lugs facing upwards, as seen in Image 1A below. The potentiometers will fasten on via the nuts that should already be threaded onto them, so simply remove the nut and washer, insert the pot shaft through the chassis cutout, from the inside to the outside, and re-apply the washer, and re-fasten the nut. There is no need to install the knobs at this stage so we will just leave them as they are.
Once pots are installed, we can move onto the fuseholder, switches, pilot light assembly, jacks etc. Here again, these will fasten via the hardware that should already be threaded onto these components -- simply remove the hardware, insert the component, and re-fasten the hardware (See Image 2A). Notice I have mounted my input jacks on the outside of the chassis -- this will help down the road when we go to wire them together. This is, of course, is a matter of preference but for now I'm going to leave mine on the outside (Image 2B).
Now we can move on to transformers. The larger transformer (power transformer) goes into the chassis cutout as it will be slightly recessed. Here you will need your 8-32 keps nuts to fasten onto the transformer mounting threads. Simply line up the threaded transformer posts with their small cutouts in the chassis, insert, and thread the 8-32 nuts on to fasten the transformer down. Note: make sure to pull all of the wire leads through the chassis as well. Refer to Image 3A and 3B below.
Next, again using 8-32 nuts and their machine screw counterparts (these should be bagged together), install the output transformer where you see the mounting holes in Image 4A. Note: Install rubber grommets in holes also indicated in Image 4A -- these are the holes through which you will feed the output transformer lead wires.
Now we will install the preamp tube sockets using the 4-40 keps nuts in conjunction with the 1/4" machine screws. There are only two mounting holes, thus two ways these could be mounted -- the orientation can be whatever you feel comfortable with, but it is advised that once you decide on an orientation, that this be uniform throughout the preamp tube sockets (same for power tube sockets). You can see the uniform orientation I've chosen for my preamp tubes in Image 5A below.
Repeat this process for the larger 8-pin tube sockets using more 4-40 keps nuts, but this time, in conjunction with the 3/8" machine screws. Once all of the above components are mounted to the chassis, we need to set up our 3-lug terminal strip for proper use. In order to do this, we need to first cut about a 2" piece of 22ga solid cloth-covered wire. Then, we will remove the cloth from the wire. Lastly, we will thread the wire through the center lug, around and through the 2 outer lugs (refer to Image 6A).
Once we have a solid terminal strip, we need to choose a place to install it. For many builders, this will be a matter of preference. For my build today, I am going to fasten this strip to one of the mounting screws on my rectifier tube socket (refer to Image 7A).
Now it's time to start populating our fiberboard. First, let's bust out our fiberboard wiring diagram, lay it on the table in front of us, and make sure the orientation of our working fiberboard matches the orientation of the printed wiring diagram (refer to Image 8A).
Once we are oriented properly, we need to open up our beautifully-organized tackle box full of electronic components. (I'm going to work from left to right). Begin identifying the necessary components on the diagram one at a time, and finding the corresponding component in our tackle box. Note: If an eyelet hole requires more than one component, try inserting the larger component first.
I like to use a pair of needle nose pliers to make a small hook at the end of my component leads before inserting them into their respective eyelet holes. This helps keep everything in place while we are stuffing the board (see Image 9A). The importance of this lies within the idea that we only want to solder each eyelet hole once -- so while we are populating the board with more and more components, we need some degree of security to prevent our components from falling out constantly.
Once all of our components are in place, we need to start adding lead wires. Take a look at your wiring diagram and notice which eyelet holes have a lead wire running off of them and out to another component somewhere in the chassis. Then, go ahead and cut enough pieces of wire to accommodate all of these leads. I like to cut my leads around 4" long to give me enough wire to route wherever I need. Make the same hooks at the end of the wire, and push the lead wires into their respective eyelet holes. Once you've done this, your board should look like the board below in Image 10A.
Finally (for today), we need to install and solder in our jumper wires. Jumper wires can be seen in the diagram of your fiberboard as semi-transparent lead lines connecting one eyelet hole to another. The reason these are illustrated this way is because these jumper wires will be installed on the backside of the fiberboard.
Flip the board over, make sure you still have a grasp on the board's orientation so you don't make the wrong connections with your jumpers, and start identifying jumper connection points. Once one end of a jumper wire is inserted into the proper eyelet hole, you should be able to solder this eyelet, as the jumper wire should be the final component for each eyelet. Now that your first jumper wire is in place, you can solder the eyelet (refer to Image 11A). Once the solder cools, give the jumper and any other lead wires a very light tug to check the integrity of the solder connection.
Continue down this path of cutting your jumper wires to length and soldering them in. Once all of the jumper connections have been made, you can solder in the remainder of the eyelet holes. After your solder connections have been made, you can clip the excess leads for a nice clean looking board. You should now have a board that looks like the one seen below in Images 12A and 12B.
Alright alright alright! It's time to take a break for now -- I think we've all earned it. Join us on our next episode where we will mount the fiberboard, connect our input jacks and wire our board out to the other components in our amplifier! It's gonna be exciting so you'd better not miss it. See you soon!