Exploring Electronics - What's inside your appliances?

Douglas Alpenstock wrote:Re the oddball screw: usually I can clamp onto these with small vise-grips and turn them out. My 2c.

My welder also has 3 capacitors about the size of a D battery! I think they would be for delivering the amperage to strike an arc more easily. Don't lick those like you would a 9 volt.

Mike Barkley wrote:Actually, the L1 marking by the green component indicates it is an inductor. Sometime called a coil. Here's the color code for those.  https://www.basictables.com/electronics/inductor/inductor-color-code

It looks like there are some diodes & a simple integrated circuit of some sort on that board too.  D9 is the diode & U4 is the IC.

T usually indicates a transformer but T6 doesn't appear to be a transformer. The manufacturer might be calling a coil a transformer there. Or it might be a misprint. It looks more like a diode but it doesn't have the cathode stripe.

CX might be some kind of proprietary component. That's not a standard designation. Is it ceramic? It kind of looks like a power resistor.

F1 is a fuse.

Capacitors are usually labeled with a C. Some of those are marked with E. For electrolytic? I guess ZhuHai does it their own way.

Another thing to note on this board is the RoHS label. That means restriction of hazardous substances. Specifically lead solder on circuit boards. Which means if it needs soldering use silver solder & the appropriate flux or the board will likely be destroyed trying to fix it.

Mike Barkley wrote:
If they are hooked together in parallel it increases the amperage & the capacitance. If they are hooked in series it is to increase the voltage. Either way ... don't lick them!!!

Thomas Dean wrote:
My coffee pot stopped working.  It was just a standard coffee pot.  I couldn't see buying a new one... I took it apart, hard-wired the electric cord directly to the heating unit (same unit keeps the bottom of the pot warm and boils the water to put over the grounds)  Now, it runs when plugged in, unplug when done.

I recently "repaired" a fan by cutting a hole in the cage that usually blocks the blade. It's so you can get your finger in there to get the blade moving initially.

Mike Barkley wrote:

I recently "repaired" a fan by cutting a hole in the cage that usually blocks the blade. It's so you can get your finger in there to get the blade moving initially.

AC motors often have something called a shaded pole. It's a small piece of shielding inside the motor to cause a tiny bit of electromagnetic disturbance. If the motor magnets happens to stop in exactly a neutral position between the coil windings the electrical unbalance helps insure that the motor starts. Do you hear anything rattling inside the fan?

Do you think the shaded pole got knocked loose or something?

Mike Barkley wrote:

Do you think the shaded pole got knocked loose or something?

Yes, a very good chance it did.

Cam Haslehurst wrote:
Also, what ground my gears was seeing one of these.
Snips
Anyways, hope you enjoyed and learned something. I like writing about this stuff!

Mike Barkley wrote:Any interest in kicking this up a notch with explanations of inductors & capacitors? How series & parallel components interact? Or something else along those lines?

William Bagwell wrote:
If your going to pursue this long term, search for "security bit set". Have a 100 piece set in a nice case that comes in handy from time to time. See almost the same with an added handle for $15 and a 214 piece set for $31. Actually bought it for tiny Torx and the smallest was too large, had to buy a smaller set of just Torx...

And yes I did! Both enjoy and learn.

I could do a whole little mini series if that sounds good. It's good for me to really cement the concepts in my head and to teach some folks on here some of the basics of how stuff actually works.

I thought it was some sort of magic

John Weiland wrote:

Douglas Alpenstock wrote:Re the oddball screw: usually I can clamp onto these with small vise-grips and turn them out. My 2c.

While that's true, it does nothing to release the inner rage at finding it there in the first place.

I actually have a small silver crow bar that I use for other applications; on this one, I would have taken some silicone  lubricant and used an eyedropper to get past the rusted screw  into the  hole and waited about 15 minutes, gotten my  small needle nose pliers and  then worked that screw out.

Stefanie Chandler wrote:I had a deal with my kids when they were still kids.  If they found it, it was yours.  If you could fix it. You could keep it or you could sell it.  When my son was 12 or so he saw a clothes washer on the side of the road.  I made him go up and ask if it was trash.  It was and he was thrilled.  When he opened the back the belt had fallen off.  He put it on and put tension on the belt.   he pugged it in and it ran.   He sold it for $75; then he was really thrilled.
Now he owns his own business.  He makes the BIG BIG Fish tanks you see in hotels and restaurants.

Kenneth Elwell wrote:Another component to be aware of is a “thermal cut out”, basically a fuse for heat. I replaced one in our round food dehydrator last year, it’s a $3.00 part, that bricks the whole machine.
In this machine it was crimped into eye terminals along with the leads to the heating element (which was riveted through these eyes to some heat shield boards). I managed to pry the crimping open and close it again with pliers, but that was skill and luck! Crimped connection is ideal since heat (from soldering) could ruin or shorten the life of the new TCO. Using heat sinks and a light touch would work, but that’s more soldering skill than I have right now!

Roger Bradley wrote:

Kenneth Elwell wrote:Another component to be aware of is a “thermal cut out”, basically a fuse for heat. I replaced one in our round food dehydrator last year, it’s a $3.00 part, that bricks the whole machine.
In this machine it was crimped into eye terminals along with the leads to the heating element (which was riveted through these eyes to some heat shield boards). I managed to pry the crimping open and close it again with pliers, but that was skill and luck! Crimped connection is ideal since heat (from soldering) could ruin or shorten the life of the new TCO. Using heat sinks and a light touch would work, but that’s more soldering skill than I have right now!

Something I always ask myself when a fuse goes is "why". They don't fail for no reason - unless it's very badly designed - so you are seeing a symptom of a problem. Thermal cut-outs are a bit of an exception as they generally fail if the equipment is being used outside of its "normal" parameters.
I would recommend a decent crimping tool as a poorly crimped connection can, because of resistance, generate heat which can cause fire. Many house fires are caused by poorly fitted power plugs - a loose screw connection (Live or Neutral) can generate a lot of heat! Hence the moulded-on plugs.

Ebo David wrote:
You know I always grab things that I think I can use for something.  Some of my friends even turn it into a game...

One day a friend walked up to me and handed me a couple of radiator hoses he just replaced on his car (these were the old ones, and one of them was blown near it went into the radiator).  He said "what can you do with these?!?!?"  I sat back and thought for a moment, ran off and grabbed a tape measure, and shouted SCORE!  He said, "ok... I just HAVE to know -- WHAT are you going to DO with THAT?"  I explained that I was in the middle of rebuilding a turn of the century player piano one of my great-grandmothers left me.  It turns out that the connecting vacuum line has an elbow that is 1/8" smaller diameter than the hose.  I explained that I could replace the vacuum hose connection with parts cut from the elbow.  A few days later I brought him a picture of the elbow installed...

Other than that, my family tells me that I have the best garage sale find of all time -- I got a 1901 rail road safe for $1 but the sales tag also read "BUT YOU HAVE TO MOVE IT".  My car was already loaded down with stuff, so I removed the door and drove it straight to a locksmith to work though.  I arranged to store the base at a friend's of my mother garage.  Then the next time I was in town I picked up the safe (minus the door).  Mind you, the safe and my home were about 1,200 miles apart, so it took a little doing...

Oh yea, then there was the time I was working as a journeyman machinist.  The shop got a small job in and we did not have a specialized to to cut a large outer radius.  I was able to hack a single-use tool together from a warn out file, ash from the wood stove, and plunge-cut the radius using a boring head.  Took an extra hour, but saved something like $400 purchasing one, AND the several weeks it would take to get one shipped to us...  Oh yea, the boss told them it would be out of the shop in a couple of days...

Kenneth Elwell wrote:
Another component to be aware of is a “thermal cut out”, basically a fuse for heat. I replaced one in our round food dehydrator last year, it’s a $3.00 part, that bricks the whole machine.
In this machine it was crimped into eye terminals along with the leads to the heating element (which was riveted through these eyes to some heat shield boards). I managed to pry the crimping open and close it again with pliers, but that was skill and luck! Crimped connection is ideal since heat (from soldering) could ruin or shorten the life of the new TCO. Using heat sinks and a light touch would work, but that’s more soldering skill than I have right now!
The construction method is made to go together and not come apart. This is perfectly reasonable, but also requires some problem solving to repair. Often the clearances won’t allow for additional bulk (of wire nuts for example), and relocating this component would negate its importance. (As would bypass/jumping the component, although both would allow the machine to “operate”, just without the safety device)

Roger Bradley wrote:
Great fun article - thumbs up for having a go. Safely!
I have always loved "fixing" things - the list is endless and some were successes, others failures. In my 30s I did a retraining course as a Prototype Wireman. It covered basic things like properly soldering a joint and moved on to cover electrics and electronics. I loved it and had a lot of fun, working in many fields of electronics and computers. I bought a ZX81 computer kit and taught myself machine code programming on it. Later in life I was fortunate to work for a company that gave me day release to get an electronics HNC. Now I'm retired and I help a group who do repairs on almost anything transportable, to save it going into landfill if possible! It's great fun and very satisfying when a "dead" item can be fixed. I've also been given all sorts of machinery that needed fixing - petrol strimmers, lawnmowers, drills - the list is endless, and I have a good range of tools for little money.
The security screws are helpful to stop the over-inquisitive from perhaps harming themselves. If you are serious about repairing things then the right tools are available for little money and take a lot of the struggle out of gaining access to a poorly gadget. A reasonable multi-meter is a very useful multi-purpose tool. I have one with a non-contact voltage indicator - plug the item in and hold the meter on the power cable where it disappears into the gadget and you can see immediately if the fuse has gone.
Have fun and fix things - but do it safely. The instructor on the Wireman course had some good tips: keep one hand behind your back when working with live equipment (a current of a few milliamps across the heart can kill!): and, it's the volts that jolts - the mills (milliamps) that kills.

Kenneth Elwell wrote:
It's as if the manufacturers acknowledge that some folks want to snap the ground post off on purpose, and welcome new purchases to replace strained cords!

Cam Haslehurst wrote:

Kenneth Elwell wrote:
It's as if the manufacturers acknowledge that some folks want to snap the ground post off on purpose, and welcome new purchases to replace strained cords!

Do you know why people do this? My only reason I can come up with if trying to plug in to one of those very old receptacles without the ground hole. Most plugs without the ground pin are polarized anyways, so it isn't like you can flip them around...

James Alun wrote:
In the AV industry, it's often done to reduce hum and buzz. It works by breaking "ground loops", these are a bit beyond the discussion here but basically you've got lots connections and lengths of wire in an earthing system. When an induced current ends up on your earth wire, those resistances cause a voltage to form and in badly designed equipment, that voltage gets into the first amplification stage of the equipment and makes a noise that you don't want (gross oversimplification)!. You might come across this especially in guitar amplifiers and other tv or pa equipment.

If you see this, then you do not let the person who did near your stuff! The best way to sort this would be for equipment designers to catch this in their designs. The easiest way is to cut off the earth pin. The slightly more expensive but infinitely safer way is to spend a little cash on an isolator. This is just a transformer, or 2 if it's a stereo signal, that sits in the signal line between the 2 pieces of equipment. Because the earths connect to either side of the transformer, they don't physically touch to create the ground loop and this is called 'galvanic isolation'.

On thermal fuses, if you've got something with open heating elements (fan heaters) that doesn't get used for long periods of time, dust builds up on the element. When you then turn it on the dust 'burns' off and sometimes the thermal fuse will blow. You can speed up future repairs by  getting a 'terminal strip' or chock block, cutting the plastic off and using this to mount the new thermal fuse. If it happens again, just unscrew the terminals and replace the fuse. Much easier than trying to do crimps without the right tools!

No professional should ever stoop to cutting off an earth pin and no amateur should be brave enough to try!