How Do You Repair a Board?

Circuit boards are just as vulnerable as any part of an HVAC system. They can fail for any number of reasons over time. Everything dies eventually. Now, the question is, you can repair just about anything with enough work. You can remake the windings in a shorted motor or alternator with enough patience. If we throw money, time, and talent at a circuit board, how do we repair it?   The contents of this post are for informational purposes only. We want to highlight the work that goes into repair. Have a professional repair your circuit boards. We are not responsible for any consequences of you doing your own repairs.   Some Basic Concepts All the parts on a circuit board are interconnected in a very specific way. Connecting them any other well will make them short out and do nothing useful. For example, imagine we have a little computer chip. It has 8 little legs, called Pins. The first pin on this chip will turn a screen on and off. The next leg will control a relay for the furnace. The next two are for a button. There’s two more for a temperature sensor. Lastly, two pins are for power and ground. We need to wire this chip into all these components somehow. On the one hand, we could plug in wires or solder wires between everything, but that will quickly become a rat’s nest of chaos. Just soldering […]

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Why Do Electronics Fail?

Your HVAC system has countless little controller boards and electrical components driving it. There’s the boards in your thermostat, furnace, and in some cases even in your pumps, just to scratch the surface. These boards do all burn out eventually, but the weird thing is that, there are no moving parts in them TO burn out. What’s going on?   Anatomy of a Circuit Board Let’s take apart one of these circuit boards and see what’s going on. The backbone of this whole thing is the PCB, Printed Circuit Board. This is that flat chunk of plastic that everything else sits on. It’s the thing you normally hold in your hands. These boards are basically copper and plastic, that act as wires, connecting multiple parts together. There’s traces of copper on the board that go from one item to the next to the next. PCB’s are pretty long-lived, but they have their weaknesses: chemicals, voltage, and physical stresses. If there’s too much power going through one part of the board, such as from a power surge, it can blow out one of the traces. If there’s anything at all corrosive that leaks onto the board, it’ll eat the traces or even eat a component of the board itself. Sometimes, this even happens from components on the board themselves, capacitors and batteries can leak corrosive fluids that will cause complete failures. In retro electronics, it’s actually pretty common to “re-cap” a […]

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What Kinds of Capacitors Are There?

Like everything else in the world, there’s more than one way to shear a sheep.. Or make a capacitor. We need something that stores a charge and quickly blasts it out. There are it turns out, a lot of ways to do this. Each type of capacitor has its own special advantages and disadvantages. Three Major Types We can broadly break capacitors down to three varieties: electrolytic, ceramic, and film. These all store and discharge power, but they come in different packages and do it all a little differently. Electrolytic Capacitors These are the big capacitors that power your compressor motor, sit in your computer’s power supply, and otherwise do heavy-lifting. They’re generally cylindricaly shaped and contain a liquid electrolyte between metal plates in a coil. The major advantage is in scale, these capacitors tend to start at a micro-farad and go up from there. Their major limitation is in frequency. They really cannot be used above 100khz. This limits them to ‘slow’ applications as power supply components. Ceramic Capcitors Higher frequencies call for a faster, solid-state approach. These capacitors are composed of ceramics and metals, often layered like a sandwich back and forth inside a surface-mounted package. This type of capacitor is very difficult to replace, it’s a tiny component on a circuit board, requiring expensive microscopes and soldering equipment to replace. When these fail, you’ll normally replace the entire board they’re on. These can be found in the […]

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How Do Capacitors Fail?

Capacitors are solid state, right? They’re just, little tin cans that do stuff to electricity, they shouldn’t really fail. How does something fail when it doesn’t have any moving parts or experience any stress? It’s not like the capacitor is burning, melted inside, or being changed every time the air conditioner kicks on, right? Chemical Changes It turns out, there actually is a great deal of stress on capacitors: heat. The hotter an environment is, the shorter that capacitors lifespan. Internally, most capacitors are not all solid. There is a (typically) liquid substance, an electrolyte, which plays a key roll in the movement of electricity through the capacitor. This liquid is sensitive to the temperature. Overtime, the electrolyte can break down when it’s exposed to prolonged heat, outside it’s operating temperature or near it’s rated maximum. It’s just like leaving your cookies in the oven at 500 degrees for 5 days straight. You’ll come back to find not cookies, but a broken down, charred pile of dust that smells more like your grill than food. We can design the electrolytes for a variety of temperatures, but most are meant to peak at 140C or so. It’s nowhere near 140C outside. The trouble comes in when you put these capacitors next to hot equipment, without enough airflow. The mere act of using the capacitor will cause it to heat up. Energy moving through electronics will always create waste heat. If you […]

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What Does a Capacitor Do?

We have capacitors in pretty much everything. They’re in your electronics to act as filtering mechanisms and they’re in your air conditioners and industrial equipment. What could be so versatile that it’s basically everywhere? Storing a Charge Capacitors are essentially short term batteries. They generally store small amounts of power, charge quickly, and discharge quickly. In cameras, they’re used to create massive charges that power the camera’s flash. The battery cannot provide power fast enough, but it does have enough power. A capacitor is capable of discharging it’s full charge in fractions of a second, making it ideal to provide a boost to the flash. Why can’t batteries work like capacitors? Capacitors don’t store a charge chemically. They store their charges electro-statically. There’s two metals inside a capacitor, separated by non-conductive material. Charge flows into one metal, creates an electromagnetic field, and the other metal converts that field back into electricity. If this sounds like a transformer, you’re on the right path. The key difference here is design. The capacitor isn’t designed to change voltages. It’s designed to store power in a magnetic field. This is essentially what makes it so fast to charge and discharge. You can have power built up inside that just needs a way out. With batteries, the challenge is getting the power out, electrons can only move so fast in the dense battery chemistry. That issue isn’t present here. Use in Air Conditioners Inside an […]

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Electrical Fire Safety

There are a ton of safety devices that are preventing you from being shocked, from starting fires, and from destroying expensive equipment. The problem is, no matter how many safety devices we put in the building, something is always going to go wrong. When things go wrong, it’s essential to be prepared for the absolute worst.   Causes of Electrical Fires The absolute root cause of electrical fires always comes down to energy. The copper wiring carries electricity, electricity is energy. The movement of electricity always creates heat. More electricity means more heat. When things go wrong, there’s too much electricity or not enough insulation to contain the electricity, or some other fault that allows heat to build up or electrical arcs to occur and start a fire. This can happen any number of ways. There can be an electrical short, perhaps water getting into a non-GFCI bathroom or kitchen outlet. There could be something shoved into a socket that really doesn’t belong there, thanks to an overly curious toddler. There can be corrosion, causing an electrical short. It could even be down to a cheaply made product skipping out on essential internal safeties (this happens more often than most people realize). In all of these cases, there’s going to be a battle on two fronts.   Stopping the Power and the Fire If you’re not quite thinking straight, you might try to extinguish an electrical fire with water. The […]

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Electrical Measurements Explained

What does 24 Volts, @ 15 amps mean? What is a watt? What’s a watt-hour? What about an amp-hour? These are all crucial ways of measuring how much electricity is present, at what rates, and just how much that electricity wants to move. We are going to be greatly simplifying these concepts, so as always, consult an electrician before working on or making any electrically involved decisions. Volts and Amps We’re going to start with the basics: What’s in the wire. The wires around you contain electrons. The movement of these electrons is electricity. When there is electricity, such as a light switch being turned on, electrons are moving through  the wire, creating magnetic fields and heat, among other things. Volts are the amount of force pushing those electrons. A low voltage source such as a double A battery has just enough force inside it to make electrons move through a wire. It doesn’t quite have enough force to shoot electrons into the air and make lightning like an industrial transformer could. The flow of these electrons is called Current, which we measure in Amps (amperes). It’s easiest to picture the current as a flow-rate, “one gallon per hour.” We can measure the total amount of amps with an Amp-Hour. For example, if we have a pump that needs 10 Amps to run, and it runs for One Hour, that it runs at 10 Amp-Hours. In 24 hours, it will […]

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How Does a Solenoid Work?

At it’s heart, an electric motor is converting a pushing and pulling motion into a rotational motion. The coils on the rotor all pull in opposite directions from opposing sides, which makes things spin. What if we didn’t have opposing sides and we weren’t trying to spin? We’d make the ‘rotor’ pop up and down instead, wouldn’t we? Applications This […]

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The AC/DC Motor

AC and DC Power are different beasts. This has been covered here before and it’s covered to death in training courses for contractors. They seem like oil and water. If you put AC power into a DC application, it’ll end in tears. If you put DC power into an AC application, it’ll end equally in tears. Somewhere along the line, there may even be a ball of fire, some sparks, and an explosion if you mix AC and DC. That begs the question: HOW can one motor work happily with both AC and DC power? It seems a little counter intuitive.   The Expected Problem In a motor using direct current, we expect the power to always move in the same direction. We use commutators to manipulate where that power flows so we can change the magnetic fields, cause changing attractions, and force a rotor to spin. What if we used AC? The field would be reversing rapidly, changing sixty times a second or more. One instance it’s forward, the next it’s backwards. Intuitively, you’d think this sort of power would create vibration. The rotor should lurch right and left a few degrees violently rattling about until something finally breaks. This isn’t the case, so long as some accommodations are made for the different type of power. Like all things, we need to be clever about where we put our wires.   Accommodating AC Power in a DC Motor For […]

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