All You Need To Know About Zener Diodes To Fix Stuff! And TVS Diodes... How Zener Diode Works
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- เผยแพร่เมื่อ 18 พ.ค. 2024
- LER #225 All you need to know about ZENER DIODES to fix stuff This is the 5th video in this series looking at common components and circuits, from the perspective of a repair hobbyist / technician.
In each video I hope to teach you all you need to know about the most common way in which components and circuits fail, and how to test and diagnose these faults. I try to keep each video to around 30 mins. Of course I will still be making the regular repair videos this channel is getting well known for.
The ALL YOU NEED TO KNOW Series
Resistors
• All You Need To Know A...
Capacitors
• All You Need To Know A...
Inductors
• All You Need To Know A...
Diodes
• All You Need To Know A...
Zener Diodes
• All You Need To Know A...
Transistors
• All You Need To Know A...
ATX PSU
• All You Need To Know A...
Amplifiers
• All You Need To Know A...
MOSFETs
• All You Need To Know A...
Thermal Cameras
• All You Need To Know A...
Power Adapters
Part 1: • All You Need To Know A...
Part 2: • All You Need To Know A...
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Thank you
Richard
50mA at 27v is 1.35W and your diode is only 400mW....
Kris Willems
Yes but No but.... The maths is right but your conclusion is not. A lot of folks misunderstand how a constant current source works. Just because a 50mA Constant Current source can deliver 50mA, it doesn't mean that it will *always* deliver 50mA. It just means that 50mA is the *most* it will deliver.
If you watch on my bench PSU current meter, as the Zener voltage increases the current decreases. So when I'm testing a 2V 400mA Zener diode it is delivering 50mA but when I am testing a 27V 400mW Zener diode at 17:30 it is only delivering 20mA. OK so this is 540mW which is a bit over the rated value but it didn't damage the Zener diode for the period of time I subjected it to the current. When I tested a 30V Zener the current on the bench PSU does not even register (less than 10mA) but the meter still read the voltage.
I also did mention at 15:10 that it would be better to change the resistor on the short finder to 100R for accurately testing Zener diodes.
@@LearnElectronicsRepair that is because your constant current source only works reliable up to a certain voltage (your bench power supply voltage minus a few volts for the minimum voltage of the regulator in the current source), which is a bit of a gamble. A constant current source of 50mA will do everything possible to deliver 50mA, independent of the load. The limiting factors are the maximum current and maximum voltage you use as a supply for the current source. The thing that has saved you is the maximum voltage of your bench supply, which was insufficient to make your current source reliable (at such high voltages). I just wanted to say that you should know what you're doing when using this method. If you would have checked a 20V 400mW zener this way, there's a chance you would have blown it up, because your current source would have had no problems delivering the 50mA. In this case it would be necessary to change the limit of your current source to a lower value by changing the resistor, as you suggested.
In other words: a constant current source will deliver the same constant current, independent of the load, up to the voltage limit it is designed for - at which point it starts behaving as a constant voltage source.
Similarly : a constant voltage source will deliver the same constant voltage, independent of the load, up to the current limit is designed for, at which point it starts behaving as a constant current source. You were saved by the limit.... In general it's better to do the calculation first and adapt your current source accordingly by changing the resistor.
" Just because a 50mA Constant Current source can deliver 50mA, it doesn't mean that it will always deliver 50mA. It just means that 50mA is the most it will deliver."
I think this is misleading, because the limiting factor is the voltage the current source has available. It does pretty much what it is designed for: delivering a constant current independent of the load up to the voltage limit, at which point the constant current source stops behaving as a constant current source and gradually starts acting as a constant voltage source. By coincidence you've reached this point....
@@kriswillems5661 Maybe it was a bit coincidental - I freely admit I am not an electronics designer I'm an electronics fixer.
However it was something I was aware of when using the short finder to test Zener diodes - but rather than doing the math I just thought, OK, I'll take the lowest voltage and highest voltage 400mW Zener diodes that I have, within the capabilities of my PSU maximum voltage, and see what happens. No Zener's were harmed during the production of this video so I decided it was OK.
Actually I did make another Zener tester video just using batteries some time ago - check that one out too if you llke
th-cam.com/video/fuCJpt_Vfto/w-d-xo.html
Worked with electronics 30+ years and I still love watching your videos. Never believe you know everything, there is always something to learn. I wish I had videos like this when I was learning, so clear and precise instructions / advice. Keep up the good work.
Thank You
You are a great teacher, I'm learning a lot from your channel. Thank you for your videos.
What I love about this video is that it directly goes to the practical applications and shows what common zebra diodes look like.
In electronics/electrical engineering we had to solve 100s of numerical problems on zener diodes & study it's general structure, characteristics , VI graphs, parallel or series combinations etc but not even one student knew what a zener diode looked like in real life.
I think education should have both.
b888
Yeah this is exactly why a degree in EE (which I don't have by the way) will not teach you how to fix stuff 😉
Makes me remember the days when I used a zener in building my own powersupply. Refreshing video, thanks for uploading.
Oh man you are a treasure thank you
You are very welcome
Your method of explaining is excellent.
This video is very informative.
Thank You
A good video, thanks for sharing your knowledge
amazing video, very good teaching.
So that short tracer is useful for testing zener diodes too that's very nice!
Another great video 👍
Love your videos, your a great teacher. At the start of the video you mentioned that your not sure why they use a 'k' for cathode. The German word for cathode is Kathode (K) which is probably how that came to be. Keep it up and thanks for all the information 😄
from the Greek κάθοδος (kathodos) K - big number of international-universal words are taken from Latin or Greek
very cool. Thank you very much !
Another great video rich,to us novices you explain it far better than most on yt carry on🦆lol
Sir,
Bundles of Thanks...
Respect and Regards,
From Pakistan ❤️
Most anticipated for me. Thumbs!
Yeah sorry it took me a little while to do this next installment - people keep sending me stuff to fix! Next one is a biggy - All you need to know about transistors to fix stuff!
I'm thinking hard how to get that down to just what is essential, without missing out anything important.
It's like a woman's skirt, it needs to be be long enough to cover everything and short enough to be interesting 😁
@@LearnElectronicsRepair Great videos Rich, Honestly mate the best on youtube. My advice for maximum coverage is to include the transistors "body diode" and how it works. Thank you*
You are a great teacher😊 It's been like ages ago, That i went to school and learned about electronics. Now i am 42 and started to hobby around with vintage stereo equipment. I come across so many obstacles like: reading the parts values inside an amp from like all kinds of different capacitors/diodes/etc. And also trying to figure out what replacement part would be suitable too if the one inside isn't available in the exact same form. Is there a way to contact you, So i can send some pictures and info on what i can read of some parts and get me started on this a bit more? That would be awesome. I also found some zener inside an Akai amp which was like rusted through, I cleaned it and for test sake i soldered it underneath the print (because legs were too short now) so i could go on with testing the project😉😊
HI. I am just trying to repair old Denon Amplifier which seems to be massively faulty. Right now I found damaged Zener diodes (works like resistor 7ohm-no diode detection). 27V tiny type MTZJ27A and MTZxx . WIth J it is 5mA Zener current without 20 mA as far as I found. Is it important to replace fully identical (5/20 mA)?
It is 27 V diode probably 500 mW tolerance A. Voltage is number one to check but what about Wattage and tolerance. A bit bigger Wattage should be not a problem What about tolerance. A seems to be the worst one. SO each replacement 27 V and close to 500mW should be OK ? Newbie in electronics (oldie by age). Great tutorials Have seen already few. Thanks.
I have a zener diode RD6.2EB2, what happens when it breaks down? The 1 ohm resistor in my circuit kept burning. This is part of a voltage regulator for a reel to reel capstan motor. The circuit has 3 transistors which have been replaced.
Very nice video
So nice
Informative article. However, I was expecting a little more respecting how zener diodes are tied together in a series configuration to produce an expected regulated output in cases when you don't have the required single zener.
Devon Wilson Actually I almost mentioned that, using for example a normal silicon diode in series with a Zener to add an extra 0.6V to the output voltage (when I was discussing the emitter follower circuit).
In the end I just kept it to a repair perspective rather than a design perspective. I'll make a video about different types of voltage regulators (Linear, LDO, Buck, Sunchronous etc) sometime, and I will include the info you are asking about here.
Thanks actually you gave me a good idea for another video. 🙂
Can you teach us about high side mosfet with zener diode inside the chip and how it works?
I hope you add these all you need to know series to your learn basic electronics for repair playlist. I've added all your playlists to my library :D
Yeah, I always add my videos to the relevant play list as soon as I publish them
Hi my amazing teacher, I have a question please, I have an electronics card which was already had an SMD Zener Diod "UM" the SMD code, when I put the red prob on A and black on K it was showing OL when I get the upsidedown it was showing 0.47 on zener mode, your input please. And many thank for your channel
Thanks for the informative video. Can you put Zener diodes in parallel or series or a combination of both? Can they be used with differeing values to achieve a desired clamping voltage? I have seen various forms of this in DIY Valve audio circuits but never understood the full aspect of it nor if it was a suitable application of the zeners capability. Thanks again Cheers H
Basically there is no point putting them in parallel (as far as I know)
Yes you can put them in series to add up to a required voltage, and also put normal rectifiers in series as well (the opposite way round to the zener) to add 0.6V for every one you include in the 'chain'
From yours and another comment here I will be making a video specifically about voltage regulators soon.
Like Colin said anytime you've got identical components in parallel its there because that component can't handle the amount of current/power on its own, but by having multiple ones in parallel we can make an equivalent component that can handle that amount of power.
Like a general example would be if we have 5W going through a component but the maximum the component can handle is 2W then if we put 3 in parallel combine together they can handle 6W as the energy will distribute its self out on its own and we get the same outcome of using that component.
old question, but previous answers have not been good, so ...
Series combinations are fine.
With parallel combinations sharing of current is unpredictable. With carefully matched zeners of the same type number from the same lot from the same manufacturer sharing might be pretty good. But if you have two (say) 12 V zeners and one is "really" 11.8 volts, well within tolerance for a ±5% part at the current of interest and the other is 12.2 V, the 11.8 volt part will conduct far more current. It's voltage will rise according its dynamic resistance and current but it is still likely to take most of the current. Zeners above about 5 V are properly called "avalanche diodes" and have positive temperature coefficient of reverse breakdown (avalanche) voltage, so that helps in sharing. True zeners, up to around five volts, have a negative tempco, so heating of one makes it take even more current and heats it up more.
It is a general truism that constant voltage things of any sort don't work well in parallel but do in series, whereas constant current devices work well in parallel but not in series.
Hi sir I watch all your videos its great place to lern, recently I was repairing a printer found blown smd diode there is no marking on it, how do it find correct replacement there no schematic for pcb ??
You need to reverse engineer that part of the circuit, work out where and how the diode is connected. From that, and with some experience, you can work out the polarity and type (rectifier diode, zener diode)
I would suggest you join the LER discord server and post some pics there, or join badcaps.net forum. Both are free to join and post questions.
Learn Electronics Repair is now on Discord! Come and join the fun and let's fix stuff together, it's free and a nice place to be.
discord.gg/vam6YC8vwU
@@LearnElectronicsRepair many thanks sir, appreciated your will join mentioned forum
As always a great video.. Is there any possibility I could contact you for some tips with the problem I have? PSU-GPU related...
Sure, email electronicanaria@outlook.com or ask on the LER discord server
Learn Electronics Repair is now on Discord! Come and join the fun and let's fix stuff together, it's free and a nice place to be.
discord.gg/vam6YC8vwU
There's loads of good advice and help on there
@@LearnElectronicsRepair I have sent You an email.
What about R2k zener diode which can be it's equivalent and voltage breakdown
Hi Richard, so happy I found your channel. Subscribed! I buy and sell fitness machines (exercise bikes & ellipticals). I find that an unusually high number of the console displays for these machines have resistance circuit failures. The resistance control no longer sends proper signal to the servo motor that moves the brake magnet in relation to the flywheel (to create silent magnetic resistance felt at the pedals). I have dozens of machines in storage waiting for this repair. Can you help me learn to fix these circuits?
I were have same problem and it was a bad 103 cap.
Hi Scott That is the sort of circuit I worked on when I was repairing industrial electronics in the 90s. Email me electronicanaria@outlook.com
@@LearnElectronicsRepair Hi, I never got your name, or background. Do you have a video introducing yourself and your journey to this channel? If not, I feel there are many like me who want to know more about the master!
@@therealb888 Sure, I did that on the first ever LER video, who I am, my background, what I do and what I wanted to achieve when starting this channel 🙂
th-cam.com/video/aJZyOkxs37g/w-d-xo.html
You will see my video production has improved over the year since I started the channel
So let's say that you have a circuit board which has two obviously burned out zener diodes. The burned zener diodes have no markings. How would you figure out what voltage the replacement zener diodes should be?
@Colin Mitchell Thank you sir
Depending on the circuit find a way to find out what the maximum current and voltage will be during operation, then just get a zener diode higher than that value. This assuming that any short circuits that are in the circuit have been removed at this point.
@@Ghost572 Thank you, I'll experiment with that.
The important thing is with failed zenner and no schematic it's impossible to fix anything! and with todays SMD Corsair PSU's it's very sad, you also need to desolder them else diodes read both ways but are OK.
Mumbling. Please speak clearly. That said. Very nice content