Dave tries to find a locally sourced replacement MOSFET for a dumpster repair and battles the RS Components and Element 14 wonky search engines and parametric search engines.
The repair video: https://www.youtube.com/watch?v=SrKLVzChy9M
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Forum: https://www.eevblog.com/forum/blog/eevblog-1387-mosfet-repair-replacement-search/
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Dave's name was on a US government watch list: https://www.eevblog.com/2014/02/24/element-14-holding-orders-based-on-us-government-watch-list/
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Done.
What if you're looking for a mosfet that is something small like an SOD-123 but it doesn't have any markings on it? Is there a good way to test it to figure out what specs it has?
This is the most informative vid that Dave has done, thanks, Dave. I have a terrible time using these searches, always with no or wrong results. If Google doesn't find it, I quit looking.
Greetings Dave, I wonder if your replacement strategy and searching options can find any data on an IR 725p nothing positive turns up in searches in the UK, though the usual data sheet sites of course list it but it is obviously obsolete, and no one has the precise number, any ideas?
Thanks Dave, some nice information in there !
but … salvaging this thing which might be in the first SMPS you grab from the dumpster, that's the way to go (IMHO) faster and cheaper also environmentally friendlier 😉 (instead of produce new, package new, ship around the world 2 times ) well, let's see how far we come.
Can someone plz explain how can I calculate Rds(on) for MDF18N50 for Id = 18A?
The datasheet says Rds(on) = 0.22-0.27 for Id=9A Vgs=10V.
Okay.
Fig. 2 "On-Resistance Variation with Drain Current and Gate Voltage" has Id rated from 0 to 9A only!
Even more, Fig. 2 says that Rds ranges from 0 to 30 Ohms! wat??
STP18N55M5 relatively new "super junction" technology now are really cheap and runs much cooler due to less Rds and lower switching charges.
For parts, I always use Aliexpress. I don't even bother looking at the others anymore. 2€ for 10 pieces Delivered to Belgium. Usually that's about 11 days. Many different shops to choose from, possibility to chat with the seller and ask questions or negotiate. I usually order a bit more for my personal stock. Never been disappointed.
Dave , there is difference between
SUBSTITUTED PART , EQUIVALENT PARRT, REPLACEMENT PART ,
in electronic world they have different meaning, you use these word in wrong way, just make it clear .
Make sure you use these word in right way .
Hi, this is such a great video. However when fixing stuff it often happens that components have no proper part number on it. Like only two/three digits. Is there a proven way to properly identify them?
This is spooky, I just went through this exact procedure trying to source a mosfet from digikey on 3 days ago. Had the same problem the search box couldn't pull up the part and had to do parametric search.
"its gonna be completely equivalent"
> Fast forward 3 days to him bricking his TV when subbing in the replacement transistor
OK, so if I understand you correctly, if the main values is correct then it should be OK to replace it with but what if you got a MOSFET of let say, 600V, 25A, 95mA, wouldn't that be even better?
Better values thus lower heat and if your very lucky cheaper… or…. could that ruin the whole thing?
Thinking of RDSon and such things but if those also is OK….
This is as I'm thinking of mine own projects… it might be more expensive etc. but it might hold longer and that is what I'm aiming for.
For one or two projects the price won't matter, I do understand of you're going to make thousands and sell, but thinking for private projects in a small scale….
Oh forgot… this is for searching for components by their max values, so if I would look for even "higher/lower/better" values then for me, that would be better but I've seen vids that you "must" have the exact value or it ruins the build and now this video that again tells me that most values ain't that important, well except the VERY important 😛 😛
I bet if you print yourself a regex cheat sheet and play around with it might work aswell. 🙂
You know, I've never payed attention to MOSFET part numbers and when you pointed out the nome- nom- er – nculture damn naming convention I grabbed my bits and odds box and had a look – and yeah it is fairly consistent. Wow now I've got an idea of some parameters of those buggers at a glance.. But hey Dave i think you should make a video explaining your expressions. Thought of this after i heard "shits and giggles" which i used to hear a lot in QLD but not so in NSW. Like for example what is the origin of "nothing burger" is it a nation wide expression. Anyhow could be fun for…well shits and giggles.
Cheers.
I can't stand it when search engines "correct" me. "Did you mean…" NO!
Hello there new to the channel and enjoy your videos. I'm looking to start repairs myself and could really do with a little help. I have bought a few broken xbox one s systems. How can I find the right size smd caps with correct values, resistors etc to get replacements. If your able to assist with a video that would be greatly appreciated
Obviously there are problems available that I never expected. Just go to Australia and you can find them out.
Mouser has a pretty good search engine and shipping is super quick since I'm only about 200 miles away. That part is half the cost here in the U.S. But that is a given.
The quality of search engines on websites is the only data point I need to understand why Google is a multi-billion dollar global company. They seem to be the only ones who’ve figured out how searching should work. Unfortunately. 🙁
Sorry to sound like a douche here.
I don’t think you gave bad advice here. All generally sound commentary. But, I’m a little surprised you payed so much attention to matching part numbering systems instead of filtering by actual specifications.
In the number of PFC front ends I’ve designed, there are surely other parameters that matter…like gate charge/input capacitance and other dynamic parameters. For a one off repair, sure, we can mainly forget about EMI implications, but shouldn’t downplay the importance if switching performance for switchmode application.
“18A being over-spec’d” isn’t necessarily true. MOSFET continuous current ratings should be taken with a large grain of salt. They are given assuming the case temperature can be held at a particular temperature…which is often not realistic given realistic heatsink design/size. For a 100W PFC, the current is probably only like 2A anyway.
Finally, back to my first point, I have not found the part numbering system used in this MagnaChip part to really be consistent throughout the industry. I have found this to be more popular
(ABC) manufacturer prefix
(##) max voltage (60=600V)
(D) manufacturer designator, maybe for package type or other
(###) rdson in milli-ohms
(E) manufacturer suffix, maybe for package type or other
So for example: IPA60R280P7
I remember when (Geezer: "When I was a boy…") the 18N50 was common as clarts. Wasn't that one of Great Scott!'s go-to MOSFETs for a while?
Had a manufacturing company find a farnell part in stock last week that I couldn't find with a parametric search. Going to try and retrace my steps and see what went wrong.
Hey Dave, would you please talk a little about the isolators useful for switching to the metal tab version. I was searching myself a while ago and, not being familiar, It was unclear to me which materials were intended for thermal properties and which were for isolation.
I hope element14 cuts you in for the increase in sales resulting from you divulging the secret options of their search form.
You could have just bypass the PFC circuit entirely on that TV psu board, or source the FET from a spare board.
Being in Canada, I only buy from Digi-key. $8 for next day delivery with no headaches.
The rest can suck it, with their ridiculous shipping charges.
Yes RS search sucks, If I cant find something on RS I google the part then RS and it usually takes me to where I need to be
"Avalanche energy in the megajoules…" and that is how Dave accidentally let slip which mosfet drives the z machine lol
RS search engine is horrible, sometimes i cant find the part i just bought. And one time i bought a part and when it came, the correct partnr. was on paper in the box. When i called them they explained that the storage department doesnt have the same system as the online site. Try searching for "Maxvu16". They sell that bloody thing but you have to use google to find it at their site.