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	My Treasure - "Tube amp making course" By Otomeijin (September 23, 2005) Chapter 2: Vol. Have your eyes opened. Topics on the work process and soldering Up to the last time, this course introduced to you the preparatory knowledge on amp making. This time, let's start the practical parts, the first of which is "soldering", the most important part of this kit assembly.
Let me start with a topic on the work processes: 1. Check the component parts of the kit. Check to see with the parts list and circuit drawing if all the parts are delivered to you. In general, a kit includes the parts list, but this kit does not. Probably this is because they thought it would be better for you to make the parts list by yourselves. I made the parts list for this kit using a PC by myself and checked with it. Of course, the kit includes all the necessary parts without any wrong part. 2. Mounting of parts and screwing This is a process in which a transformer, condenser, vacuum tube sockets and terminals are installed on the chassis. In this kit, they are already mounted before delivery, so check to see if there is any looseness or bending in the installation and try to learn how the structure is and how to install by observing it so that you can install them next time you make an amp by yourselves. 3. Wiring process This is a process in which parts are connected with one another based on the circuit drawing. In general, you do it by soldering, pin sockets, and terminal connection. The main part of amp making work is soldering, so the completeness of the finished amp depends upon whether or not the soldering is well done. Once you have learned how to solder, you will do it easily. In the "Special Course" later on, you will learn how to improve your technique in soldering. 4. Check the wiring. Check to see if the parts are installed correctly as shown on the wiring drawing and if they are connected correctly. 5. Measure, adjust, try out and complete! Insert the vacuum tubes correctly and check by a tester a few voltage values indicated on the circuit drawing. Then, give a load on it and adjust it to minimize the humming. Finally, play back the vocal sound on the amp as a tryout, and if there is no trouble confirmed, the amp is finished. (See the previous "My amp making".)
--"Special Course" on soldering-- The manufacturing industry of electric appliances requires a high level of know-how and cost in terms of mass production and quality gurantee. But in our case, you do not have to worry once you have learned the basic technique because the parts to be soldered of our amp are not so many. There are many ways of soldering according to each person, including merits and demerits. "Otomeijin's method" is based on my past experience, so please feel at ease. Learn it step by step.
My apology for placed photos in this course: I have no demonstrator or photographer to help me and take photos by myself. So all the items on the photos are just placed on a flat table just to show you their images. They are only something like a rough sketch. (My written instruction has reached an expert level, though my technique as a photographer is far from that level to my regret.) The photo shows my preparatory items for this course. On the left is my single-focus camera. The others are a magnifying glass which I bought at a 100-yen shop, and a triangle corner stand with a height that is different by 1cm from the focus point of this camera. Well, then, which is the camera by which I took this photo? I purchased another camera as extra equipment for this course. Next week, I will use this new camera.

1. Explanation -Solder: This is made from tin and lead. You melt it by heating and use it for soldering. The melting point depends on the composition of its components, but in general, it is between 180 and 220℃, I suppose. There is a solder paste, a chemical agent that makes soldering easier. But do not use the paste too much, because it has a function to clean metal and damage the metal by remaining in the metal for a long period. As a result, it can cause loose connection or disconnection. The attached string solder is easy to use in general. The string solder includes safer resin (flux) in its center, so you do not have to use the solder paste. -Soldering iron: It contains an electric heater inside which heats the iron, and is used to melt the solder and to put the melted solder on the joint parts. It is not that you melt the material of the part itself such as a lead wire but that you attach the melted solder to the part. I, "Otomeijin", dub this attaching process "plating". Some others call this process "adding solder". The latter sounds good but it tends to let you add too much solder. In fact, adding too much solder is no good. For amp making, 30 through 50W is better depending on the iron size and heat capacity. There also is a soldering iron of 500W for casting, but it would scorch the amp. -Attention: The soldering iron becomes heated more than 300℃, so be careful not to burn or scorch yourselves or other materials. In addition, be careful not to melt the solder too soft in order to prevent melted solder dropping. Therefore, you need to prepare an iron pot and place the iron on it or "plate" on it. As an iron pot, I use a junk pottery dish or ash tray. A concave of an ash tray for putting a cigarette can be used for placing the heated iron. (See the photo.) A simple stand also has a concave. Another type of a stand is also for sale with a hole in which you can insert the iron tip. A sponge is for sale as well to clean the iron tip after it absorbs water.

2. Recommended method -There are many ways for soldering procedures and "plating". For example, one way is to connect the joint parts together at first and to solder them in one move, and another way is to "plate" them at first and to connect them later. (See the following photos.) Here I would like to recommend you "Otomeijin method" because it is proved to be a secure method by my past experience. In the "Otomeijin method", simply put solder on or "plate" the joint parts beforehand. This is described as a "preparatory stage of soldering" later. (See the largest photo of the three below.) As you know after trying it out, you can use only one hand freely in soldering with another hand grasping a soldering iron. So, pinch a part with a pair of pincers, melt string solder with a soldering iron and attach the melted solder to the part. -The most important point A: Connection by heating can be something serious to an electronic part. Sometimes soldering can scorch the part like "yaki-tori". It does not actually scorch it, but the damage is invisible so it is troublesome. Damage can occur at the joint or surface inside the part and lead to malfunction. Semiconductors and a condenser are especially weak against heating! Then, how can we do? Decrease the heat or cool the heat. -By going through the "preparatory stage of soldering" described later, shorten the soldering time. -Pinch the wire with a pair of tweezers or pincers and solder it to the weak part by cooling the heat. -As soon as they are connected, cool them down by blowing. Point B: Never move the joint parts before the melted solder becomes solid. If the melted solder is moved before becoming solid, it becomes white and incomplete with a crack.


3. Wrap-up1 Now it is over about basic procedures of soldering. Let me show you specific steps in practical work in the "preparatory stage of soldering". -Before connecting the parts, "plate" the terminals with melted solder. Regarding the lead wires, cut or bend them according to the wiring length or position, and then "plate" them with melted solder. These two are the major part of soldering. -Check: This "preparatory stage" must be repeated for every part and lead wire, and after the "preparatory stage", the "final soldering" must be repeated for every part and lead wire. -Cut a lead wire based on the wiring length. The cover of the wire must be removed at both edges by 5mm. Like this, you can twist the copper wires without damaging it by your oily palms. Then, "plate" it. Be careful not to make copper wires disbundled. In order to remove the cover: (1) Make the lead wire roll on your finger and remove only the vinyl cover with a knife or (2)Remove the vinyl cover by inserting the wire into a hole of fit size of a wire-stripper. (2) is the quicker method, but the problem is you may cut even the inside copper wires as well if the hole is too small. (See the photos below.) -In "plating", if you have the part in one of your hands and grasp the soldering iron in another, both hands are occupied. You need to melt a small portion of solder with the soldering iron and immediately attach the melted solder to the part. Ideally, the part, soldering iron and string solder must be put together three at once. You have only two hands, so bend the tip of string solder into a crescent shape, move the part near the solder, and "plate" them all together by the soldering iron. Unless copper wires or the joint part is dirty or oxidized, you can "plate" them in the former method. Cut away the rusty part or polish the dirty part. -Open the back lid of the kit, and go through the "preparatory stage of soldering" as aforementioned for each of the lag terminals, socket terminals, terminals and volume terminal.


Now "Special Course" is over. However, if you immediately begin to solder the parts, you may make a mistake like scorching the part. So practice at first using extra copper wires or terminal-sized copper board in order to understand how much solder is the best, how to handle or turn the soldering iron. Then, you will learn "how to get a secure and beaudiful finish of soldering". Do not use too much solder. If the "necessary part including the surrounding" is all "plated" thin and in silver color, the "preparatory stage of soldering" is over. (See the photo.) Do not forget to take preventive measures against "yaki-tori" (scorching the part). Now that you have understand the key points, let's do it actually. Never do it hastily but complete it in a secure manner. To be continued.

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