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How To Find The Value Of A Burnt Open Circuit Unmarked Resistor

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Sometimes we find a faulty PCB where resistors have burnt, blackened, cracked or the markings are obliterated because of the component running hot. Often these resistors will read open circuit on a multimeter but we need to know the correct value so we can fit a replacement. So how can we we do this if we have no schematic and the value of the resistor is not marked on the board? There a number of ways we can approach this such as reverse engineering the circuit to calculate a reasonable resistor value but here is another good method we can use.
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Опубликовано:

21 авг 2024

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Комментарии : 179

@Pulverrostmannen 10 месяцев назад

Ha ha very nice, Glad to see you try my method, A bit rough on making the score but after some practice you learn how to make it depending on resistor type, it is often enough to scrape it a bit with a file or knife or even just poke it off with a screwdriver. Sorry about the long name :P it is a Swedish equivalent of "Powdered Toast Man" But in Swedish you say it in one long word but more like: "Pulver-Rost-Mannen" Great video!

@stefflus08 10 месяцев назад

Hi powdered cheese man 😂 That's what I read, didn't see the R in the middle

@Pulverrostmannen 10 месяцев назад

@@stefflus08 aahaha believe me you are not the first one on that, But I actually pick this name because of how funny it is and that I like getting a good laugh from all the confusion around it lol

@LearnElectronicsRepair 10 месяцев назад

@@Pulverrostmannen Hi there Powdered Toast. It was really good to see your suggestion and it was a pleasure putting it out to a larger audience. Credit where credit is due and thank you. 🙂

@Pulverrostmannen 10 месяцев назад

@@LearnElectronicsRepair It was my pleasure! credits goes to the other viewers that mentioned this as well in the other video. It is a great feeling we all gather here together to learn from each other. Together we get smarter and more experienced every day :) keep up the good work!

@LearnElectronicsRepair 10 месяцев назад

@@Pulverrostmannen Abcoultely 100% That is the great thing when we form a community. And thanks again.

@tomluque 10 месяцев назад

In 1967 high school electronics class we were taught to use a small triangle shape file to notch into a carbon resistor to remove carbon till we had the resistance value we needed, then use nail polish to seal the cut. I'm now stunned while watching this video that I did not think of chipping away the body of a wire wound resistor to measure the coils to estimate the value of a burn-out resistor. Thank you.

@jennyearl5194 10 месяцев назад

Think resistance increases when filed. I was taught, seen and did this but so long ago I cannot recall exactly. But resistors were massive devices 30 mm long and 12 mm diameter with spot colour codes. Crystals ex gov were taken apart and adjusted in a similar fashion with a blade and nail varnish. Don’t think I ever did that so cannot say how they worked afterwards, but it was a very popular way of getting ww2 equipment working.

@andymouse 10 месяцев назад

Yep it does indeed increase and its a common trick back in the day !@@jennyearl5194

@andymouse 10 месяцев назад

Nope, fact done it myself....get an old carbon comp and see for yourself...easy.@@krystal5887

@johnrhodez6829 10 месяцев назад

Great untill the resistor is tottaly exploded! But then you proberbly have other problems elsewhere in the circuit!

@andymouse 10 месяцев назад

Yeah ! no magic smoke left in at all and everywhere else is getting hot ready to realise the smoke ! @@johnrhodez6829

@dang48 10 месяцев назад

Nice new trick there. A big thank you to the folks who posted these suggestions.😁👍

@retiredtech9846 10 месяцев назад

Great idea! Thanks to all who suggested it and to Richard for doing the video.

@englishrupe01 10 месяцев назад

Fantastic. Many thanks, Richard.....and the other guys that suggested this. I never knew this was possible as a method. Great stuff.

@Tutterzoid 10 месяцев назад

INstead of a dremel tool, Sandpaper or even a screwdriver edge I have used to remove the paint or coating to do this method, but thanks for sharing that more people can fix things, instead of them landing up in landfills

@chongli297 10 месяцев назад

I love this. Together with the previous video on working with an unknown circuit, this really shows that there are practical methods of overcoming any challenge in electronics diagnosis and repair!

@d614gakadoug9 10 месяцев назад

Film type resistors aren't necessarily physically symmetrical. The spiral groove that is cut to actually set the resistance starts at one end and finishes where it needs to, which may be moderately far from the other end. This is clearly visible with the resistor in the video starting at about 12:00

@d614gakadoug9 10 месяцев назад

@@lurch789 Huh? If you have a point it is very far from apparent.

@Dutch-linux 10 месяцев назад

Nice learned something today thanks Richard and the guys who suggested this

@g4z-kb7ct 10 месяцев назад

I've done a similar thing with ceramic-coated small vertically-standing PCB modules like those used on that air conditioner board. In this case extreme care is needed so I very carefully scraped away the ceramic coating with a segmented knife. After about 5 minutes the knife went dull so I broke off the dull segment and kept going with a nice sharp edge. After about 2 hours the whole thing was uncovered then I reverse-engineered it and made a new PCB. So yeah instead of the heavy-handed approach just scrape away some of the coating _gently_ ^_^

@smithjohn4853 10 месяцев назад

A diamond contactor file is a slower but more presise way to grind away the ceramic ( I use these a lot in my job to repair large expensive contactor contacts )

@sylkelster 10 месяцев назад

Use alligator test lead on one end connected to meter, place resistor firmly on table and use more pressure with needle tip for more stable readings, me thinks.

@annaplojharova1400 10 месяцев назад

This works with many resistor types, but it could be heavily misleading with certain resistor designs, mainly when laser or grinder trimmed or with certain wear/failure modes. Sometimes the film just gradually oxidizes, so increases its resistance. When it degrades so much it breaks, its resistance could already be way off. Sometimes the trimming does not form such regular spiral, but a kind of mesh of parallel stripes (mainly on HF low ESL resistors). Then you get it practically only when the last stripe from the multiple parallel ones broke, then you will measure pretty bogus value (depends on the exact trimming pattern). So you should keep in mind this and be aware about it. Good way is to look where the resistor is used and what values use to be used in such cases. And be prepared for the "extracted value" to be wrong, so prepare a set of tests to confirm the value you came up with is really suitable (check the voltages/currents in the circuit, whether loading of the components in the area is not suspiciously off).

@LearnElectronicsRepair 10 месяцев назад

I agree. No method is perfect or even suitable for every occasion, but I don't think that means this method has no merit or use as it clearly works very well in some situations and that has to be a good thing yes?

@JurassicJenkins 10 месяцев назад

Brilliant - I couldn’t resist ⚡️

@pault6533 10 месяцев назад

I’ve been in this situation, the color codes were all browned they were not readable. Thanks for composing a video about it!

@ronangel8194 5 месяцев назад

Those probes are also very useful for removing dirt from under the thumb nail!

@kevinroberts781 10 месяцев назад

This is fantastic! Thank you for the education Sir!

@leso204 10 месяцев назад

Old school thinking still works today 👌

@islandhopperstuart 10 месяцев назад

Splendid: what a great tip!

@tonysheerness2427 10 месяцев назад

You learn a new trick everyday.

@photohounds 10 месяцев назад

Interesting result! As it's not burnt, I'd have immediately suspected the End caps

@kriswillems5661 10 месяцев назад

Think so too.

@CliveChamberlain946 10 месяцев назад

Never thought of that! I suppose filing or chipping away the epoxy, albeit *más suave* we'd see the break, short the leads, and measure 99% of the resistance directly across the break. I think these are called laser-cut "thick-film" resistors, as opposed to the beefier wire-wound type.

@LearnElectronicsRepair 10 месяцев назад

Yeah I was a bit heavy handed in my attempt. But it did show the method is good, thanks again to the viewers who suggested it 🙂

@d614gakadoug9 10 месяцев назад

It is unquestionably a film type resistor. A wirewound resistor in that resistance range would have a very large number of turns of very fine wire. There are two common types of power film resistors - metal film and metal oxide film. The former generally have better stability but the latter have better transient overload handling ability. Wirewound generally have both good stability and transient overload handling ability but they are considerably more expensive and become impractical for high resistance. The inductance of wirewound can be a problem in some circuits.

@CliveChamberlain946 10 месяцев назад

@@d614gakadoug9 I'd imagine film thickness on that one might be used from 5k to 22k since on one end, the spiral cut was far from the end cap. I've seen rectangular wire-type in some applications - I think these are wound using the Ayrton-Perry format.

@Lightrunner. 10 месяцев назад

Good forensic research👍👍👍👍

@antonypalmer5804 10 месяцев назад

Brilliant even if this is not perfect it would put you in the right ballpark. I've worked in electronics for years and this had never occurred to me. Definitely some think worth mentioning to my apprentices.

@SolderBrothers 10 месяцев назад

Great diagnostic, thank you, love that stuff very much.

@athhud 10 месяцев назад

Glad you got into electronics and not surgery on humans! Lol it was quite frustrating watching you poke all AROUND the conductive part of the resistor. With my nitpicking out of the way, I GREATLY appreciate you sharing this idea. I will definitely put it to good use! Now if only there was a technique for SMD capacitor values. . .

@johansvideor 10 месяцев назад

Great idea! I've tried adjusting resistance value of metal film resistors with a small triangular file. You increase resistance by removing material. If you do this, might be a good idea to cover the cut with solder mask or something similar.

@echelonrank3927 10 месяцев назад

this works badly for small resistors or anything over 100 ohm

@jeisonsanchez4842 10 месяцев назад

Thanks for following the suggestion, Richard. I really wanted to see the outcome. I cringed a bit as I thought of the chance that the resistor could come out flying the moment that the grinding wheel touched. If you do another video on this topic, can you cut open a working resistor and measure that one as well?

@LearnElectronicsRepair 10 месяцев назад

Gonna make a followup to this one on the next live stream @theelectronicschannel 22nd October 5pm London time with Carlos and Detlef, let's burn some resistors and see if we can still measure the value

@zyzaxxxch 10 месяцев назад

Nice, Definitely a nice tool in the toolbox, even if it might not work for every resistor, depending on its type, how it failed and 1/4W or less will make it harder. Maybe swabbing it off with a bit of Iso might make for less intermittent when trying to read solid meter readings.

@kenmichaels1842 10 месяцев назад

Fascinating! Great idea and demo!

@KrotowX 10 месяцев назад

Probably the best dremel ad between electronic repairman. Unfortunately not so easy to to this with burnt SMD resistors.

@LearnElectronicsRepair 10 месяцев назад

Well I like a challenge so lets try and find out 😉

@curtisroberts9137 10 месяцев назад

Great idea from your viewers. Thanks for sharing!

@smichels5117 10 месяцев назад

Fascinating and VERY useful! Thank you all!!!

@jrmiller034 10 месяцев назад

Great Information. You bring great information in all your Videos. Thanks!

@arthurfricchione8119 10 месяцев назад

Thanks for sharing Richard 👍

@davet3804 10 месяцев назад

I have some diamond coated dremel bits of many shapes .. they allow very precise and controllable work .. ideal for this .

@jagc1969 10 месяцев назад

Very interesting indeed. Thanks for sharing.

@dave-d 10 месяцев назад

Thank you. Nice trick. More accurate than expected.

@MikeyMack303 5 месяцев назад

Nice! Thanks for sharing that!

@colinmackay852 10 месяцев назад

nice video, cheers for the shout out !

@LearnElectronicsRepair 10 месяцев назад

You are welcome Colin. It was an excellent idea.

@PeterMilanovski 10 месяцев назад

This is fascinating.... I have an amplifier that someone was building in their garage back in the early 70's for which I don't and can't find a schematic for, it functions but it had one resistor across the main power switch which was toasted, I remember seeing the spiral band (whatever happened to it, it definitely saw some heat!) And I didn't even bother to put a multimeter across it to see if I could get some sort of reading, I closed the amplifier up and put it away for another day.... I think that day has just come around...... I have no idea why it's there, it's going to need to be reverse engineered to see what the actual function of this resistor is supposed to be for, the amplifier was hand built and named after the street of the house was at, you would never tell just by looking at it! Whoever was building these, they did an amazing job, it looks like it could have come straight out of the pioneer factory of the time.... Looks like it's going to need to make its way back onto the bench for a complete overhaul.... I can't believe that I didn't try to measure what little if any resistance could be measured! Lucky I still have this little piece of Australian history... Back from a time when we actually used to make stuff and were pretty good at it too!

@LearnElectronicsRepair 10 месяцев назад

Good luck and nice to see this method may help you 🙂

@garygranato9164 10 месяцев назад

i wouldnt have thought of doing that. ! very impressive :)

@BlondieSL 5 месяцев назад

Sometimes, "old school" is just the best way. I mean, it always worked before. 👍😁👍

@Martyn-ey9lw 10 месяцев назад

Excellent idea, every day is a school day

@Ezzell_ 10 месяцев назад

Great video....great tips

@brano2yt 10 месяцев назад

Absolutely love this type of content, thank you. Btw, seems the invalid traffic bug is because of too many people running adblocker. At least Sorin thinks so after last video.

@elvendragonhammer5433 10 месяцев назад

Instead of using a cutoff wheel I recommend geting a set of diamond coated Jewlers bits. One of them should look like a super tiny version of a cutoff wheel but the top is completely flat. The side works for rounded ones & the flat top works for surface mount resistors, capacitors, & the like.

@echelonrank3927 10 месяцев назад

i always used a regular knife to leave the resistance tracks intact, and now i find out there is a professional option for the job🤪

@mikemorrell7921 10 месяцев назад

Awesome. Thank you for sharing

@jamesmdeluca 10 месяцев назад

Greetings: If the burned/break is narrow enough! Set up for a normal resistance reading from lead to lead. Use good mechanical alligator cllips to ensure reliable contacts. Then use a conductive pick to find and bridge the actual break resulting in a reading through the break to the meter, possibly a more accurate reading? If the coils are only thin then finding the break may require removing the insulating portion further around the resistor circumference. My guess is that the mfr process here is similar to laser trimming whereby the coils are made while measuring the lead to lead resistance while the coil separation is increased and stopping at the appropriate measurement.

@wherami 10 месяцев назад

yes that was quite interesting and good to know. thanks!

@monberg2000 10 месяцев назад

Brilliant!

@gianlucadm 10 месяцев назад

wow! thanks,I've learned something, today.

@SomeGuyInSandy 10 месяцев назад

Super useful!

@stevebabiak6997 10 месяцев назад

Since it is wirewound, it’s open segment will likely arc across if a sufficiently high voltage is applied across the terminals, and the arc being left in place long enough should cause some charring at the location of the arc (and the break in the wire). The high voltage supply should be current limited to be on the safe side.

@midwestrepairdesk 10 месяцев назад

Ingenious.

@edwinwaugh 10 месяцев назад

What a very interesting method, love your videos 😁

@pmcrisp 10 месяцев назад

great fun to watch

@GiC7 10 месяцев назад

Thanks, great teaching

@paulmeynell8866 10 месяцев назад

That’s brilliant thanks so much.

@Dutch_off_grid_homesteading 10 месяцев назад

Heya, wel never tought of that but yes that's a possiblity. nice job well done and thanks for sharing

@Enigma758 10 месяцев назад

Love it!

@christopherjackson2157 10 месяцев назад

Very nice ❤ Tho i find i run into this a lot more often with surface mount resistors than with through holes

@jayfowler4747 10 месяцев назад

OK I use the blade type soldering tool.... I'm sure you know the one I mean just press on the coating and it chips off... if its a wire wound you need to be careful, the wire can come away with the coating, a dremel is too aggressive.... if its ceramic the coating just falls off but you need to measure both sides as I've had odd results with those.... but yes it can be very helpful when you have no drawings..... you can see on the example you have why the half way method won't work...

@charlessmyth 9 месяцев назад

That worked out pretty well :-)

@savvy2807 10 месяцев назад

Great vid.. never even thought of that.

@jozsiolah1435 10 месяцев назад

Components addict to the circuit board, when installed or soldered onto it. Mainly you can see all this difference in chargers, smart batteries, power banks, solar phone chargers. Components have a default value, and the usage, charging calibrates diodes, resistors to support your needs. If you misuse your chargers or batteries, the components become worse, until it becomes useless, but you can still fix it again. That is caused by the smart batteries, if the user is monitored, the components become memory effected due to a satellite laser radiation. Professionals, engineers simply can’t believe this. Even mechanic simple motors can gain memory effect in the copper coil, and can be fixed by offloading the motor, and it takes 30 minutes repeated retry. This is so new, nobody even knows this. The whole problem is caused by the user’s behaviour, or money grabbing.

@Salfke 10 месяцев назад

Very interesting method, i never thought about this one 😂

@ravenclawavenger2170 9 месяцев назад

If the resister has color bands thy tend to a lovely shade of brown. Look the resistor and rotate it. There may be spot where the color 'is in tact. Suppose you find a resistor where the first band is light brown It must have been yellow. How does yellow occur? Usually with purple to for 47.

@imark7777777 10 месяцев назад

Cough personas. I picked up a brand new almost never used interface the problem is the power supply. When issue is that there is a quarter white resistor that gets a little too warm so I have no idea what the value was and had to pick up another unit but even that has a discolored resistor. And the company is absolutely no help. I've managed to. Use a close approximation to what the value of the second unit was only to find out there's something else wrong in the power circuit the only rears its ugly head under load. If I swap power supplies the other unit works fine.

@ridefast0 10 месяцев назад

Great content, thanks ;-)

@Drew-Dastardly 10 месяцев назад

Dremel is a bit brute force for this, a diamond file should be more than enough. However it is a great technique.

@geoffrey4513 10 месяцев назад

nice one

@googledoesntneedtoknownone 10 месяцев назад

If you have no specs available you also don't know the tolerance of the resistor either. "Back in the day" when 12AX7's and 6L6's ruled the earth 20% resistors were typical - in tube circuits of hundreds of volts what mattered was that (for example) the plate voltage was "large" compared to the screen voltage. In that case, deducing 20K for a 18K value would be just fine. With many modern circuits values of 1% might be absolutely required. Hopefully you should get a feel for the required tolerance by knowing the function of the circuit and perhaps by looking at the still working components.

@bones1225 10 месяцев назад

Nice one😊

@teslasapple 10 месяцев назад

Amazed 🎉

@iconoclad 10 месяцев назад

When you started probing you got just over 7k from one end and just over 10k from the other end, so you already had your answer - 18k.

@traditionaltools5080 10 месяцев назад

Generally you can just scrape enough coating off with a knife blade. Just uncover the wire and replace with a standard value.

@GaetanoCostanza 8 месяцев назад

Best tool to use to grind with is a grinding pen nf V2 from eBay etc

@kriswillems5661 10 месяцев назад

Nice trick. Looks like poking and scratching it until the outer ceramic layer breaks off is more effective than that dremel.

@I_Don_t_want_a_handle 10 месяцев назад

The dremel is a starting point, maybe?

@Dutch_off_grid_homesteading 10 месяцев назад

@kriswillems5661 do I know you ?

@deriknovella8419 10 месяцев назад

This is great, but do you have a solution for SMD's, as all the new stuff is coming out with SMD's and no schematics. Hope there is someone out there that has an idea.

@des2610 10 месяцев назад

Should have clamped the Dremel and held the resistor at both ends..more control that way....

@I_Don_t_want_a_handle 10 месяцев назад

It's also a good way to have it end up whipping away to a couple of hours of hide and seek.

@des2610 10 месяцев назад

@@I_Don_t_want_a_handle Resistor flying off???...... You need to lift your skills and become a Master Technician mate! lol It's easier to control a tiny resistor than a large dremel.....

@I_Don_t_want_a_handle 10 месяцев назад

@@des2610 take them overly strong troll hands back under your bridge 😜

@des2610 10 месяцев назад

@@I_Don_t_want_a_handle Keep practicing son! You will reach Technician status one day! Then..... you can work to become a ******Master Technician***** like me! Then your resistors will not fly off when you try to grind them!!!

@I_Don_t_want_a_handle 10 месяцев назад

@@des2610 is it all in the wrists?

@1pcfred 10 месяцев назад

I'd think to break brittle ceramic crushing or smashing it may be best? The ductile resistive element should survive the abuse.

@chrishartley1210 10 месяцев назад

+1 on this method and then use a hand file from a jewelry file set if necessary.

@d614gakadoug9 10 месяцев назад

The resistive element, which in this case is metal film or metal oxide film, will be somewhat ductile but it is formed on a hard ceramic cylinder which will break. Usually the coating on these small resistors is pretty soft. You can use long nosed pliers to carefully crush it to allow picking it off bit by bit. If you encounter a wirewound resistor with vitreous enamel coating you'll have a heck of a time getting the coating off. I would score the resistor in the middle and try to snap it in two. Usually that leaves the two pieces connected by some wire that unwinds, but not always. (Markings on viteous enamel resistors are often fired on along with the coating so they are very resistant to burn-off.)

@MoreCharactersThanNeeded 10 месяцев назад

Haha, "Pulverostmannen" is Swedish for the powder cheese man.

@louf7178 10 месяцев назад

The cracks look to be more on one side. If this is accurate, can you say if it was installed with that side touching the board or not. Is it better to install something with a gap or not? (Just built a Blue ESR meter, and tried to leave a gap on anything.) Thx.

@Derek_Garnham 10 месяцев назад

Great content, but three years too late for me. I just guessed from the charred remains and noticed another of the same value nearby. - Didn't work but eventually found a diagram.

@LearnElectronicsRepair 10 месяцев назад

Without doubt there are several different and good ways to approach this problem

@machineman6498 10 месяцев назад

👍

@hermannschmidt9788 10 месяцев назад

Interesting how the resistor still wouldn't reveal its faulty spot after having shed all of its coating.

@Hitek146 10 месяцев назад

I always just broke them in half, and then measured each half, probing around the broken cross-section...

@phonotical 10 месяцев назад

Getting a reading from the middle out is a terrible idea if the wire had burnt the it's thinned before it's broken

@pb5640 10 месяцев назад

You would have had better luck if you had scraped off the black corrosion of the one lead which is non-conductive. Buy some alligator clips for the end of your probes.

@BlondieSL 5 месяцев назад

I use alligator clips all the time. I have some really nice ones that have the plastic ends where you just insert the probe tip. And the clips are much better quality than those cheapy basic clips. Simply a must have in the lab.

@ARian-ks2xu 4 месяца назад

I'm new to electronics, I have a board that a bad diode caused a overheat in the resistors. Three resistors grouped together all burnt completely black. I get a reading from all three but it's different on all three ones 54 ones 56 and the last one is57. No schematics for the board I have scoured the internet will it be safe to assume that I could replace these with 5.5 resistors?

@LearnElectronicsRepair 4 месяца назад

Are these three resistors all connected in parallel with each other? What is the device?

@TYGAMatt 10 месяцев назад

That's a pretty good idea. Might have to kill a resistor just so that I can open it up😊 I'd be tempted just to try and give it a little tap with a toffee hammer just to get it opened up and then pick away at it

@cliffjones7868 10 месяцев назад

But how about a carbon? It was mentioned to use a file and change the value so If you used your cutter and just uncovered the carbon somewhere near the center you should be able to accomplish the same.

@BlondieSL 5 месяцев назад

I've never had luck with carbon resistors. Usually, by the time they are totally open, they have literally overheated and the carbon turns to bits and pieces. Sometimes, we get lucky and a burned up carbon resistor just splits in 2. That makes finding the resistance a bit better.... *MAYBE!* I say maybe, because again, once a carbon resistor gets that hot to fail, the entire carbon will now not measure as when it was new. If you get my meaning.

@wojciechbajon 10 месяцев назад

And now SMD version. Those small, who hasn' markings on it. XD

@LearnElectronicsRepair 10 месяцев назад

Yeah let's try that 😁

@I_Don_t_want_a_handle 10 месяцев назад

As a novice in this area (new hobby) it has struck me that resistor values are somewhat odd. I'd took them to be something like RAM, i.e. having their values jump in weird unfathomable increments, but if it is just down to material and windings, why are there no 20R resistors? Why can one not buy resistors at any value? Just commercial usages?

@inseries5494 10 месяцев назад

;try to imagine being a manufacturer, and count how many nominals you're going to produce! hint: infinity

@ivolol 10 месяцев назад

You can definitely buy 20R resistors. Look up "E series of preferred numbers" on wikipedia. The conundrum is, we may arbitrarily want any peculiar value of resistor, but it'd be absolutely wasteful manufacturing to try to create every single rational value of resistor for every power of 10. So the E series of values is used to space them out approximately, in more of a log than linear scale. The higher the E number, the more values are available to create a scale between 1 and 10. 2 (* 10 = 20) is a value available in the E24 series. Although if you pay enough to a resistor OEM for a large enough order, they certainly will manufacture a batch of resistors to almost any value you'd like.

@theelmonk 10 месяцев назад

It's not feasible to make or stock them in every possible value, so a subset is chosen. I think the actual values offered are some sort of log scale : in general lower values are more clustered together. The ranges are called E6,E12,E24 etc; E12 are the most common, precision resistors are E24 or better and E6 only may be offered in some high power parts. E12 has all of E6 + some in between, same for E24 and E12, etc etc. 2.0 occurs in E24 but not in E12 or E6, hence the comment that it's not available (in this type of resistor). Capacitors also follow this scheme and use the less precise values (E6, E12) as capacitors generally have wider tolerances than resistors. en.wikipedia.org/wiki/E_series_of_preferred_numbers So there's method behind the madness .. they're not really unfathomable, just like RAM sizes. There's a reason, you just haven't learnt it yet. For RAM, it's because every extra address wire doubles the number of cells possible.

@davidrobertson1980 10 месяцев назад

If you search hard you can buy any resistance value, but each tolerance range has a table of "preferred values" If you want a 20R resistor buy a 1% or lower tolerance and you can get it.

@I_Don_t_want_a_handle 10 месяцев назад

@@inseries5494 ... And you could try reading the whole post.

@ACommenterOnYouTube 10 месяцев назад

How about a simple video showing an appliance or something that does not power up and do a basic trouble shooting video to find the fault ???

@Stelios.Posantzis 10 месяцев назад

That won't work with carbon composition resistors though, will it? Another take on this: chip off the enamel, rather than using abrasion, starting from the caps. This way you run less of a risk of eating away at the resistive layer.

@bofor3948 10 месяцев назад

It might but you will need a very fine probe point and a steady hand. After all thats how carbon track linear variable resistors work.

@LearnElectronicsRepair 10 месяцев назад

@@bofor3948 I think it will work too. More live streamed experiments on this topic @theelectronicschannel 5pm Sunday 22nd October London time

@d614gakadoug9 10 месяцев назад

I agree about working from the end caps inward. Some resistors have an extremely hard coating that is very hard to remove, but on film types its usually fairly soft. In any case, starting at an end cap gives you an idea of what you're up against. With a carbon comp resistor that has failed due to excessive power dissipation I suspect you'd have a hard time coming up with any useful measurement. Even after gross overload carbon comp isn't too likely to go completely open-circuit. With one in good condition cutting a tiny V down to the element in the centre of the body would work quite well since the element is a uniform "slug." But then doing that with a known-good resistor isn't really very instructive.