OPTO 6 - POTENTIOMETER WIRING

 

Welcome to my blog, which is solely dedicated to providing ya'll with a laymen's explanation of whatever it is you may have questions about.

We have been receiving a ton of inquiries concerning the building of the historic LA2A, so the next few posts will be dedicated to just that.

The first step, logistically speaking, is to order your parts. Once they arrive, do yourself a favor, and take a deep breath. As a layman myself, I find it is easy to get overwhelmed by a build.

Now, let's get to the fun part.

There is not a specific place to start, per say, I just chose to start with the potentiometer wiring. For this part of the build, you will need the following tools and supplies:

1. Latex Gloves (the board is tin/lead coated... and lead poisoning is a bad thing)

2. .032 60/40 rosin core solder (silver solder sucks, don't use it)

3. Respectable soldering iron (Weller or Haiko)

4. 2 conductor + shield or 3 conductor + shield FOIL shielded wire (do not use braided wire)

5. Wire strippers

6. Heat shrink tubing (assorted sizes, as you will need several sizes)

7. Wire snips

8. Two (2) potentiometers 

I like to label my potentiometers, so I don't confuse them, as their placement dictates which pins will have the long wires attached. That being said, cut two (2) lengths of your shielded wire to 14", and another two (2) to 18". Strip one end of all the wires, roughly about an inch and a half or so. This doesn't have to be exact, as the other side of the wire will be cut to length later. The focus is that you have given yourself enough room to work with. 

 

 Snippin' wire.

Snippin' wire.

Once you have stripped all four (4) wires, pull the foil down, give that baby a few twists, and snip it off. You will notice a thread hanging out, go ahead and cut that as well. Take a moment, and look at how the shielded wire is set up...

 Stripped shielded wire. The wire to the side is your drain wire. Do not snip this, you need it. Later on you will shrink tube that wire, but until then, look at the colors of the wires. RED. WHITE. BLACK. 

Stripped shielded wire. The wire to the side is your drain wire. Do not snip this, you need it. Later on you will shrink tube that wire, but until then, look at the colors of the wires. RED. WHITE. BLACK. 

Now that you have become familiar with the wires, and feel comfortable with the red, white, and black wires, I need you to yank that white one right out.

This is a give and take relationship, my friends...

Now, repeat that process for all four (4) shielded wires. Once you have pulled the white wire from all four lengths of wire you have cut, strip roughly an inch or so off each wire, twist the copper wiring inside so it isn't frayed. Think back to when you used to set up your boom box, and had to twist the wires to place them into the speaker jacks... same thing.

When you have completed this, slip some latex gloves on, fire up your soldering iron, and get ready to get your build on. 

The raw ends of the wires require "tinning." Not sure if this is a professional term, or just one we use around here, but when I say tinning, I am asking you to solder the ends of the wires. Solder the ends of all the ends from all four (4) wires. when completed, it should look just like this:

 

 Raw wire ends that have been tinned. Ignore the black wire in the background... you needn't worry your pretty lil' head about that guy, just yet.

Raw wire ends that have been tinned. Ignore the black wire in the background... you needn't worry your pretty lil' head about that guy, just yet.

After all the wires have been tinned, the next step is to shrink tube the drain wire. This is that wire I JUST told you to ignore... That guy needs to be insulated, or things can get hella messy when it comes to shorting out your board. Like with the other wires, you will want to leave a little bit of raw wire out so you can tin that sucker as well. Once that wire has been shrink tubed and tinned, you need to add a shrink tube to the base of wires, and covering about an inch of the grey outer part of the shielded wire. Doing so insulates the wires. 

 Example of shrink tube to wire ratio.

Example of shrink tube to wire ratio.

 Shrinking the shrink tube with a lighter. Yes, the white wire is still in my shielded wire... do as I say, not as I do, and we will get along swimmingly.

Shrinking the shrink tube with a lighter. Yes, the white wire is still in my shielded wire... do as I say, not as I do, and we will get along swimmingly.

Once all the wires have been tinned, and shrink wrapped, you are now ready to begin soldering them to your potentiometers. Remember that you have two (2) different lengths of wires... and remember how I said the placement of the potentiometers would dictate which got what wire? Well, we are at that point. Pay close attention, as you don't want to do a bunch of work just to tear it all apart, and the hair out of your head, cause you didn't. 

The LIN pot, in layman's terms is the potentiometer that is going to be the peak reduction knob, this one needs a 14" shielded wire, where the black wire (not the shrink tubed drain wire) is pulled out.

With the red wire and drain wire still in tact, make small hooks with the tinned side. Hook the red wire to position "2" on the potentiometer,. (google the pin numbers on a potentiometer... did ya think I was gonna tell you every little thing?! Come on... ), now hook the drain wire to position "1".

Take the 18" shielded wire, yank the red outta there, and do the same hook thing to the black wire and the drain wire from that shielded wire.

Hook the drain wire to position "1", and the black wire to position "3". The black wire is the one you want to be long... again, remember that conversation about long wires? This is where that comes into play.

Solder that shit. If you don't know how to solder, here is a great link on how to do so... YouTube and google are your friends, maybe even your best friend when it comes to learning things you never knew. https://www.youtube.com/watch?v=fYz5nIHH0iY

The connections should be short, and well soldered.

An alternative way to wire the drain wire with a 3 conductor + drain wire is to strip a small section of the ground wire, loop the drain wire around that spot, snip any extra wire, solder the wires, and then cover the entire section, including the base of the shielded wire with shrink tube. Sounds more complicated then it is... trust me, it is a simple move. Just remember to keep it compact... you want it to still resemble a normal sized wire.

 Example of what the soldered wires and pins should look like.

Example of what the soldered wires and pins should look like.

The LOG pot, which in layman's terms is the gain knob. For this bad boy, you need to have the 18" shielded wire with the black wire pulled out. Again, this is the ACTUAL black wire, and not the drain wire you have shrink tubed. Make those cute little hooks again, and hook the red wire to position "2" and the drain wire to position "1".  

With the 14" shielded wire, yank out the red wire, and make some cute hooks at the ends of the drain wire, and the black wire. Remember which is which... you don't wanna blow up the world cause you fudged this one.

Hook the drain wire to position "1", and the black wire to position "3".

Now, get your solder on. Do the same as you did above... with short, well soldered connections.

You are now ready to attach your knobs to the front. This is the easiest part... 

I hope this has helped you with the wiring of the potentiometers. Feel free to email me if you may have any further questions, or if you don't feel secure enough to go forward and get your soldering on... but, let's be real, if I can do this, so can you.

 Greg's diagram of how to wire... Notice the alternate way of wiring a drain wire. 

Greg's diagram of how to wire... Notice the alternate way of wiring a drain wire. 

  

 

 

 

 

 

gregory lomayesva