Component Manufacturers that you should stay away from! - Page 1
Forum section: electronics / beginners

author: Falcon69
author_rank: Super Contributor
timestamp: October 18, 2014, 04:37:18 am
content: What manufacturers should I stay away from when ordering from Digikey, Mouser, Arrow, or any other big house distributor?I know that ordering on eBay is a big NoNo from experience when purchasing electronic components. Especially IC chips, as most are fake or from bad stock, bad meaning the manufacture knows that a certain percentage is bad but sells the reel off cheap, and others sell on eBay.Take resistors and capacitors for example. Arrow has Samsung Resistors and Capacitors far cheaper then the other manufacturers, but how good are Samsung Chips?So, list a bad manufacturer of IC Chips, or passive components and list your opinion as to why it is better to spend a few pennies more to purchase from that 'other' manufacturer.

author: Dago
author_rank: Frequent Contributor
timestamp: October 18, 2014, 05:51:55 am
content: I've heard the rule to avoid the three M. Microchip, Maxim and Micrel, all known for bad availability apparently.I personally don't have that much experience except that I DID get burned by a Microchip step-down converter chip that has had pretty bad availability almost constantly.For electrolytic caps I usually use Panasonic, Nichicon, Rubycon or Chemicon (but not Kemet or Multicomp or any of that crap).

author: Simon
author_rank: Unknown
timestamp: October 18, 2014, 09:27:22 am
content: Quote from: Falcon69 on October 18, 2014, 04:37:18 amGee thanks, I can't possibly think how it is that I have many repeat customers. Seriously your saying that perhaps some of the major distributors that are still in business for a reason are so bad no one should use them ? where do you live ? under a rock.There are various reasons to use any of the distribution methods you list. Some are cheaper, some require larger or smaller minimum orders and some just have better webistes. I regularly use Farnell for myself (yes that includes my ebay shop) and work, but recently had to tell the farnell rep that I was going to use digikey for a particular order because i had particular temperature requirements and most of farnell's parametric search's don't have temperature as an option. I had to point out that granted farnell were cheaper but given the time it would take me to hand sort through the specs myself and double check all specs as farnell are notorious for errors in their listings (worse than most ebay sellers in-fact) it would take so much of my time that my employer is paying for that in the long run it's much much cheaper for a £100 order to go and buy the parts from digikey where their search features are better and their listings are very accurate even if their parts are more expensive. As it happens when i did report an error (and it was an elusive one) to digikey I got a response in 2 hours, with farnell it takes 2 weeks to get an automated acknowledgement response, but do I still use farnell ? hell yes as they tend to be cheaper and have more stock than RS but then RS often have stuff that farnell don't so yea not true answer.

author: kxenos
author_rank: Frequent Contributor
timestamp: October 18, 2014, 09:29:58 am
content: Quote from: Dago on October 18, 2014, 05:51:55 amKemet is a well-known reputable manufacturer.

author: Simon
author_rank: Unknown
timestamp: October 18, 2014, 09:31:04 am
content: Quote from: Falcon69 on October 18, 2014, 04:37:18 amManufacturers and distributors are two entirely different things also!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 18, 2014, 09:40:41 am
content: Quote from: Dago on October 18, 2014, 05:51:55 amYou are joking right?Maxim, yes, Micrel , don't know, but Microchip have always had the best availablilty in the industry.

author: Falcon69
author_rank: Super Contributor
timestamp: October 18, 2014, 09:41:29 am
content: Yes,I am talking about actual manufacturers, NOT the distributors.And in regards to eBay. I ordered some IC chips, 80% of the reel was Junk. I, myself, will NEVER order IC chips again from eBay, Unless it's an old 1970's chip to repair a tv or something I couldn't find anywhere else, even after spending 5 hours searching.Dago, why do you say stay away from Kemet? That's the reason for this post, your opinion, AND reason why? Are their parts not accurate? Bad quality? D grade compared to another manufacturers A grade or B? (letters on a scale like a math homework or test in school).

author: Simon
author_rank: Unknown
timestamp: October 18, 2014, 09:45:52 am
content: Quote from: Falcon69 on October 18, 2014, 09:41:29 amDepends on what you ordered and what you paid for them, there are chips i will not buy from chinese suppliers for that reason and use mouser/farnell but essentially you get what you pay for. For example i have just started selling ICL8038, these are obsolete and used to cost around £20 when they were "clever stuff" but now they are sold by many manufacturers as copies for much less because the original manufacturer stopped making them and same with a similar maxim chip.

author: abaxas
author_rank: Regular Contributor
timestamp: October 18, 2014, 09:56:05 am
content: I don't get your issues with ebay.Loads of great sellers but also plenty of crap ones too. Just avoid the 'we sell everything' type of wholesalers and you'll have a much better experience. Especially true with static sensitive devices.Ie if they sell electronics, car parts, hair extensions and 99p ipad cables. AVOID!

author: coppice
author_rank: Super Contributor
timestamp: October 18, 2014, 10:07:23 am
content: Quote from: kxenos on October 18, 2014, 09:29:58 amI wondered how that got in the list. If Kemet aren't good enough for you, you'll have to give up electronics.

author: ovnr
author_rank: Frequent Contributor
timestamp: October 18, 2014, 10:11:40 am
content: Quote from: Simon on October 18, 2014, 09:31:04 amUm, Simon... he said "What MANUFACTURERS should I avoid when using these distributors". Not "What distributors should I avoid".The rest: Microchip has excellent availability, I've never had an issue with Micrel parts, but Maxim is of course the joke of the industry.Kemet makes perfectly decent caps.Samsung MLCCs work fine and are wonderfully cheap, but they feel... wrong. The wrong surface texture - most MLCCs have a glossy coating, these are as coarse as cheap bathroom tiles. Not using them for anything remotely hi-rel.Personally: I've started avoiding European manufacturers of chips & such, because in my experience they tend to fuck up their datasheets on a regular basis (omissions, errors, completely bananas terms for some things, bad German translations, etc).

author: Simon
author_rank: Unknown
timestamp: October 18, 2014, 10:15:09 am
content: Quote from: abaxas on October 18, 2014, 09:56:05 amThere are many that just dropship parts from farnell and have thousands of items for sale that they don't actually stock, this shows in their extortionate prices and feedback for late deliveries or non deliveries with refunds. Some do just try and import anything and everything they think will sell with no regard for quality. Personally I build my stock up gradually, I have just completed stocking with the full E12 range of resistor values from 1R to 10M in 1% and originally started with a small selection of jellybean mosfets that I still sell. Next i will work on building up my capacitor stock hopefully financed by the christmas rush. It takes a lot of work to be a goo seller and while I have my own website people still prefer to buy from me on ebay in 99.999% of cases, what people do find when they buy from me is that I know about the parts I'm selling if they have a question and i am always happy to advise broadly speaking on suitability for use which sometimes has ended me up teaching a customer how to use the part. I had a uni student telling me he couldn't get one of my IRL540's to work with his MCU and that the load was constantly on, so i asked him for a diagram and he had connected it up all wrong and the internal diode was passing current to the load all of the time, I sent him a diagram of how to connect it correctly and he went away a very happy chappy.On another occasion i custom programmed an ATMega328 for a disabled gentleman who was a bit confused about what he wanted as he was planning to run a CNC machine which was his hobby and passion when he felt well enough from an arduino uno board with a "special version of the bootloader". What I actually found out when he told me the name of the system was that someone had devised a CNC control system using an arduino UNO board simply because the hardware made sense but the firmware was something totally different. I was happy to sort it out for him and ended up supplying the complete kit of MCU, clocking gear, bypass caps and regulator for no more than I sell them on ebay despite the research and time i had to put into sorting out the firmware for him.Some of us don't mind going the extra mile and somehow I'm often the one they contact when they want something a bit different or advice but that might be because i don't have a flashy shop front but from my listings it's generally clear that I know what i'm selling and I'm genuinely happy to help.

author: Simon
author_rank: Unknown
timestamp: October 18, 2014, 10:17:09 am
content: Quote from: ovnr on October 18, 2014, 10:11:40 amUm yes your correct. Same answer, you get what you pay for, distributors stock everything, including the good, the bad and the ugly, if you buy the cheapest they have to offer don't complain later.

author: bookaboo
author_rank: Frequent Contributor
timestamp: October 18, 2014, 10:30:08 am
content: Finder Relays.I remember doing a project for a large machinery OEM, the prototypes used OKO brand relays which I believe are Anglia components own brand, made in China. One of the OEM engineers questioned the reliability of the OKO relay based on the fact that it was Chinese and asked me to use Finder as these were used in their control panels.Not wanting to rock the boat I specified the more expensive Finder (despite never having a single issue with OKO myself). Barely 1 week after production began I got a phone call about an intermittent fault on a machine, sure enough a simple "tap tap" on the relay and the machine starts, similar problems cropped up throughout that batch.In that case they were just unreliable due to the vibration from the engine. I saw an even bigger disaster when a certain German crane manufacturer decided to solder 14 pin Finder relays into their fancy new control board, the contacts were rubbish and were a constant source of problems.

author: Tandy
author_rank: Frequent Contributor
timestamp: October 18, 2014, 10:33:54 am
content: I think it is fair to say that buying on eBay is highly variable, you have every sort of seller on there from poor kids collecting bins of dropped parts from a local factory through to respectable companies that only deal in brand new components that are fully traceable. So you can't really think of eBay as a single source it is thousands of individual sellers all of whom have to get their components either directly or indirectly from manufacturers.Where you buy your components from is all about what is important to you.For example if you are a hobbyist/maker who has plenty of time but very little money then buying a bag of 500 resistors that are more like 20% tolerance than the advertised 2% instead of having to buy 5000 from a big distributor is more than likely going to be fine. Component quality is not exactly top priority in a DIY greenhouse watering project. A majority of the components you get will work and because they are cheap you will sometimes get some that end up being duds.Similarly buying from a Chinese supplier that takes 6 weeks to arrive and may not have the same component next month when you want more is no big deal if you are just stocking up on common components for use at some future time where there are no deadlines. However if you need something for a weekend project then the convenience of having items held in stock in your local country does mean it costs more.If you are building something to sell then you need to be sure that components are genuine and comply with relevant regulations such as RoHS, if you are building on a small scale you can probably easily substitute components if your supply dries up. If however you are producing a complex item on a large scale like a mobile phone you will need to guarantee that the exact components have good availability and are fully traceable with batch numbers etc from the manufacturer so if a fault is reported in your product you can identify a bad batch of components from a supplier as being the cause.Putting aside the fake components and re-cyled sold as new that you can only avoid by buying from trustworthy sources, how do you choose manufacturer?Again this depends on your priorities, lots of small projects are often based on atmel microcontrollers because they are widely available in small quantities and somewhat friendly towards the small guy, making technical information available etc. Contrast that to broadcom that unless you have a regular requirement for thousands or millions they won't even talk to you. But if you are a large scale manufacturer you can get some highly specialised components from them at low prices.A distributor who cares about their reputation is not going to sell products that are either poor quality or consistently fail to meet the published specifications.The problem is when you go to a large scale distributor like digikey or RS you have a vast choice. If you search for a 100? resistor and are confronted with 2000 choices from 100 manufacturers you are going to be overwhelmed. For a hobbyist it is a nightmare knowing why you should choose one over another but to be honest it is not really that important for a small producer. A resistor from Samsung is essentially the same as one from ROHM. There will be subtle differences in the materials used etc that an engineer gets used to and those things are reflected in their designs. In a large scale operation a designer may choose a manufacturer because for example in their experience the tolerance of a samsung capacitor is typically -20% and rarely +20% so they take this into account in their design. Perhaps they find they have less failures with ROHM resistors when using wave soldering or due to the different quality tape they are supplied on they have less placement errors on their particular machine. Very little of this is of interest to the small scale producer or hobbyist but you may over time gain a preference for a particular manufacturers product.So I would suggest the bottom line is concentrate on the published specs rather than the manufacturer at first to choose the part that is the closest match to your requirements within your price range. Don't worry about who the manufacturer is unless you have a bad experience with a particular manufacturer and buy from a supplier you trust.

author: Falcon69
author_rank: Super Contributor
timestamp: October 18, 2014, 10:34:36 am
content: Don't want this thread to turn into a bad rant type thread on eBay or whatever. I simply would like to educate myself and others of what manufacturers of electronic components (capacitors, resistors, micro-processors, whatever) are good or bad based on their quality, longevity, service, availability, and of course, percentage of failure rates, whether you buy a full reel or just a few.For example: Personally, I've had fairly good luck with TI and Fairchild. I think out of a few hundred chips, I've only gotten a couple that have been unusable. But, then again, maybe that's why Mouser always gives me a few extra.bookaboo...pure example why expensive, is not necessarily best.

author: Tandy
author_rank: Frequent Contributor
timestamp: October 18, 2014, 10:42:32 am
content: Quote from: Falcon69 on October 18, 2014, 10:34:36 amActually that is because they can't physically count all the tiny components so typically they are weighed to get the quantity. As the weight is not accurate they will make sure the pack is overweight to avoid complaints from customers fro shortages.

author: Simon
author_rank: Unknown
timestamp: October 18, 2014, 10:49:48 am
content: Essentially it's about the bottom line. if you buy a chip like an opamp that is available from multiple manufacturers and you get the rock bottom price one chances are there was a compromise. My supplier and yes I tend to stick to one chinese supplier, he is a bit dearer than some but i trust him more and he makes a point of telling me the manufacturer when i ask for a quote, so he too understands the value of one manufactuer versus another. It depends on the use you want to make of the part, some parts of lesser quality may work just fine if you don't push them to limits, but if you know you need to be certain of being able to work up to the limits then get the slightly more expensive one. I tend to look at datasheets as a guide to quality, if the datasheet is brief and cryptic or includes too many parts on the one datasheet I tend to give them less credit.At work where as many know I'm given stupid specs I have to drill all the way down through the datasheet to check that the part will work as i expect and what it's characteristics are over temperature, example i recently built a discrete SMPS because I could not easily get a SMPS controller rated down to -50C, but i found a nice voltage ref that would go down to -55 with just a 5mV variation over the whole temperature range and the amount of detail on the datasheet and further information available convinced me that the part and therefore it's manufacturer whose name I don't remember and don't care to was reliable. So if you show me a 2 page datasheet with vague specs, I'll not be trusting you as a manufacturer of that part, because extensive specs mean extensive tests and more likelyhood that problems where avoided due to testsBare in mind that people like mouser will weigh large quantities of loose parts and if you get more it might be because of this and they err on the side of caution, I also weigh any amount over 20, with my crappy ebay supplied "precicion scales" and no complaints so far

author: Jeroen3
author_rank: Super Contributor
timestamp: October 18, 2014, 01:30:09 pm
content: Don't use multicomp for productionsince they sell leftovers from (to you) unknown sources.Don't use Block pcb transformers, they tend to heat up quite badly.

author: hans
author_rank: Super Contributor
timestamp: October 19, 2014, 08:44:09 am
content: Just never delve into the store brands for anything that needs to be in production on mid to long term. You may have based your design around this wonderfully cheap 0.1% resistor, but find that it's out of stock when you need a reel of them. Because it's a store brand of e.g RS you can't get them somewhere else. The cheapest alternative component may be several times more expensive, making your BOM cost go over the top.For prototyping I think the store brands can be fine to use.I don't think I would go on the hunt at Ebay for semiconductors, even for hobby, because of the many stories of scams I've read. You may strike lucky though..I usually stick to components I can get from 2-3 suppliers (Farnell, RS, Mouser, Digikey) in a day. I've had numerous occasions where a component would be a perfect fit (Maxim springs to my mind for being that component manufacturer) but you can get them only from Mouser and they 34 in stock. Maxim store itself has a multiple week lead time, which pretty much rules it out.

author: tggzzz
author_rank: Super Contributor
timestamp: October 19, 2014, 08:50:37 am
content: Quote from: hans on October 19, 2014, 08:44:09 amThat many and such a short time? I'veneverseen the MAX9979 available except buried in an evaluation board!

author: Zero999
author_rank: Super Contributor
timestamp: October 19, 2014, 09:49:11 am
content: Quote from: Jeroen3 on October 18, 2014, 01:30:09 pmIsn't multicomp Farnel's own brand? If it's true, then you can never be sure of the manufacturer.

author: tggzzz
author_rank: Super Contributor
timestamp: October 19, 2014, 10:13:54 am
content: Quote from: Hero999 on October 19, 2014, 09:49:11 amThat can be recursive problem. For example, if you buy an HP laptop it won't have been made by HP. Or consider LED lights, where the LEDs are made by a different company than the one that packages them, or makes the light "bulb", or puts the bulb in the package that you see in the shops. And don't even think of trying to understand what's in Verbatim's (to pick a company at random) CDRs!

author: Tandy
author_rank: Frequent Contributor
timestamp: October 19, 2014, 10:18:37 am
content: Quote from: Hero999 on October 19, 2014, 09:49:11 amMulticomp is farnells brand meaning from multiple sources. I have ordered muticomp diodes before and received some fairchild and some diodes inc. Both were the part I orderd just from two different manufacturers.

author: Kjelt
author_rank: Super Contributor
timestamp: October 19, 2014, 10:38:10 am
content: Quote from: mikeselectricstuff on October 18, 2014, 09:40:41 amMy personal experience:For small/medium production/hobbyist Microchip is fineifthe chip is already in production (never base a design on preliminary datasheets or samples from them because sometimes they just don't produce the chips).What I have learnt a few years ago, that for mass production Microchip had big issues.They have prooven in the past not to be able to deliver huge quantities of some of their processors, then postpone delivery dates over and over again. For a big company this is a no go since everything for production has to be planned and fixed months before.The nice thing about Microchip is that they keep their stock a long time so you can still order the old chips.

author: madires
author_rank: Super Contributor
timestamp: October 19, 2014, 11:28:32 am
content: Quote from: bookaboo on October 18, 2014, 10:30:08 amHave you selected the correct relay for your application? There are several different alloys used for contacts, optimized for specific applications. Have you also considered a snubber or whatever for inductive loads? I can't recall any major issue with Finder relays during the last 25 years.

author: Asad
author_rank: Contributor
timestamp: October 19, 2014, 01:23:25 pm
content: Some posts above referred to Maxim having issues. What's the issue with Maxim?

author: Tandy
author_rank: Frequent Contributor
timestamp: October 19, 2014, 01:29:00 pm
content: Quote from: Asad on October 19, 2014, 01:23:25 pmAvailability, it is no good having a part in your design that you can't get hold of when you need to run a production.

author: Bored@Work
author_rank: Super Contributor
timestamp: October 19, 2014, 03:12:23 pm
content: Quote from: Asad on October 19, 2014, 01:23:25 pmAvailability.Many nice ICs - on paper and you can even get samples. But when you want to buy you find out you can't. And then suddenly Maxim declares them obsolete. I once had the feeling the only IC they really had in production and you could buy was the MAX232, one of their oldest ICs. Everything else was a gamble.Some years ago they claimed they had fixed their supply issues. I didn't see a change.

author: Unknown
author_rank: Unknown
timestamp: October 19, 2014, 07:44:04 pm
content: With regard to eBay, I've found that if you steer clear of the sellers with incomplete or vague listings and go with the ones who supply the most information in the listing, you usually get decent stuff (not always but mostly). I've seen some nightmare listings when searching for top-ups on eBay, no part numbers/manufacturers/dimensions/links to datasheets etc... My own personal view is that the more effort they've put into listing their stuff, the more likely they are to be a trustworthy seller. I mostly get my stuff from Farnell. I'm only in to £20-£30 per order area, but I've never had an issue with them other than errors in the occasional listing but there's always a datasheet for everything to double check.

author: Dago
author_rank: Frequent Contributor
timestamp: October 20, 2014, 04:29:14 am
content: Quote from: mikeselectricstuff on October 18, 2014, 09:40:41 amLike I said, I do not have much experience with those manufacturers, this was just a "rule" I heard from our subcontractor and I mentioned it to our assembly house and they concurredAs for Kemet I might be wrong, I've always avoided it because when people ask for a proper electrolytic cap brand it never gets mentioned (usually everyone says Panasonic/Rubycon/Chemi-con) so I've avoided it.

author: Asad
author_rank: Contributor
timestamp: October 20, 2014, 06:42:03 am
content: Unless explicitly specified for usage, I avoid Murata ceramic caps. I had a bad case of wrong values shipped from Farnell and despite getting replacements twice, the values were off significantly from the one specified in datasheet and product packaging. I had to stack two to get the specified value for prototyping and swore off them since. I don't know at which place the QC/supply chain broke down on that one but now, I stick exclusively to Yageo, Kemet and AVX for ceramic caps depending on application and values required.

author: bookaboo
author_rank: Frequent Contributor
timestamp: October 20, 2014, 07:54:03 am
content: Quote from: madires on October 19, 2014, 11:28:32 am16A relay switching a 1A solenoid (fully regulated supply with suppression and reverse diode fitted, they just couldn't stand any vibration). This problem happened with no load applied as well and after barely a few hours of operation.Also there may be bias as they are such a popular relay but I've seen loads of Finders in our repair shop on various equipment, the contacts seem to be a really weak point. The good thing about them is that they have clear covers so you can easily see the black mess that were the contacts.

author: Simon
author_rank: Unknown
timestamp: October 20, 2014, 07:58:30 am
content: Quote from: Boltar on October 19, 2014, 07:44:04 pmFarnell consistently make mistakes in their listings as i commented earlier and I don't mean occasionally, it's that bad that for niche stuff I can't use them as I don't have the time to waste in doing their job for them. When I complained i was told that the information was "old and historic".I take your point about datasheets and specs on ebay listings, I probably need to revisit many of mine but ebay don't make life easy, I have tended to assume that if you come looking for an IRL540N you already know what it is and what it does. There is one seller that "drop ships" from farnell and just copies their specs, which means that will often also be wrong and contradictory or repeat the same spec under different headings.

author: Unknown
author_rank: Unknown
timestamp: October 20, 2014, 09:31:21 am
content: Quote from: Simon on October 20, 2014, 07:58:30 amNoted, I have a great deal more time to ponder the parts I want as I'm only hobby level. I guess I've only noticed occasional listing errors at Farnell because I've only really looked for a tiny fraction of parts from their inventory. With eBay specific parts, like a IRL540N, I see what you mean about people knowing what that is, so a listing need not be detailed, in many cases, so long as they actually supply a part number or model number, the part can at least be looked up. It is however, extremely handy to eBay buyers if the seller can put as much info into the listing (and in the title too if possible). For a basic example, if I type "N Mosfet" into the eBay search bar and I get a list of parts, I'm much more likely to click one that has a current rating in the title if that's the base property of the fet I'm looking for.

author: Simon
author_rank: Unknown
timestamp: October 20, 2014, 09:53:28 am
content: For many general parts yes the errors farnell make may not be a problem although I have found some very basic and damaging ones like incorrect current and voltage ratings. i looked up the microchip MCP9701 temp sensors to find them listed as +/- 1C whereas i was pretty certain that they are +/-2C as I'd used them before hence i went looking for them. Naturally the datasheet said +/-2C and they got an ill tempered report from me as the error was big the the information plainly and clearly on the first page of the datasheet.When I'm looking for very specific characteristics for my employer I can't afford the time to sift through the datasheets to confirm farnell's listing specs.Yes on ebay I tend to list main specs, with datasheet links it's so easy for them to change and break links and to host them myself and link to which I have done on some stuff is very time consuming as it's a very manual process. Ebay still think big pictures are all that count and explaining to them that I could leave out the picture and put TO220 or TO92 and it would be just as good is a waste of time.

author: madires
author_rank: Super Contributor
timestamp: October 20, 2014, 10:01:41 am
content: Quote from: bookaboo on October 20, 2014, 07:54:03 amFinder specifies vibration resistance and also shock resistance in the datasheets (please seehttp://www.finder-relais.net/en/Finder-general-technical-information-en.pdffor the definitions).

author: bookaboo
author_rank: Frequent Contributor
timestamp: October 20, 2014, 10:38:41 am
content: Quote from: madires on October 20, 2014, 10:01:41 amI'm not a mechanical engineer so I won't be able to translate vibration specifications into real world scenarios. In this situation I just have to go by cold hard experience.It may well be that Finders are designed to sit in a nice dry environment (i.e. an AC control panel) and not in the mobile machinery I design for. All I know is my little OKOK4BC12 relays have been in Sudanese deserts, outback Australia and Siberia for years without issue while in this case the more expensive Finder cousins couldn't make it out of the factory yard.ymmv

author: madires
author_rank: Super Contributor
timestamp: October 20, 2014, 11:43:36 am
content: Quote from: bookaboo on October 20, 2014, 10:38:41 amIn that case I'd have looked for automotive relays or SSRs. AFAIK, Finder doesn't produce any automotive relays but they got SSRs. For automotive relays I'd recommend Fujitsu, Omron or Panasonic.

author: SeanB
author_rank: Super Contributor
timestamp: October 21, 2014, 06:32:44 pm
content: Beware of fake Omron relays, there are a lot of them out there.ABB relays are good, but bleeding expensive, but will last pretty much forever or until you overload them by 1000% for a thousand cycles, or until they mechanically fall apart.Smallest they do is a 4 pole 16A one though, with industrial coil voltages, and low power is 6W coils.I replace them with Omron ones in plug in styles, as then it is easy to replace it every 2 years, but only for those which failed after 40 years of operation, and have over 100 million cycles on them. With us the machine does about a million cycles a year, but the previous owner ran it at 10 times the speed 24/7/365 for 20 years before they bought a new one and sold it to us. Only failures were relays that wore out mechanically, with cores that wore into T shapes, and contacts where they physically broke or the springs broke. I bought some years ago for $5, about half way through them now, replacing those that are not available in a plug in style with them.

author: XFDDesign
author_rank: Frequent Contributor
timestamp: October 21, 2014, 07:21:07 pm
content: eBayWith eBay, you're in an essentially laissez faire market. This means the onus is on you, the buyer, to understand both what you want, and what you have a reasonable expectation of paying for a given product. As a buyer, it is not a very good avenue for the complete novice who doesn't understand the difference between a resistor and a piece of wire, mainly for the reason that they are looking for keywords or buzzwords that align with what they think they need."Don't buy from china," - the second hand Rubidium Standards almost exclusively ship from China, and are recycled. As a buyer who knows, it's a hedging of bets. Do they have good reputations from others who bought the same product? Is the price within range of the other market offerings? It's a good bet, but not aguaranteedbet. Is the risk vs. reward at (now) $200 a pop worth it? Semiconductors - same thing. Do they source high volumes of specific parts, or is it a complete hodge-podge of random parts? "Everything from China is black market!" - One of the biggest "games" played by Chinese ODMs is to use a lead customer's bill of materials to get pricing down, lump in a particular part with other customers, and get even higher volume pricing to improve their margin. If their lead customer is buying 250k pieces, and their second-through-fourth customers are buying 100k pieces each for a total of 550k pieces, they may push the part supplier to sell their $0.10 LDO at 500kpieces, to sell them at $0.05 at a 750k pc order, while charging their own customers $0.15/ea. They then turn around and resell the difference in stock (200k pc) for $0.25 each, while you and I would pay $1 from Mouser. If they sell all 200k pieces, they've made $40k for what is essentially consolidating initial orders.What usually comes up, is that a newbie sees "74 series logic grab bag: 250 pieces" for $50, buys it, and most of them are dead because they're either factory floor sweepings, re-worked part pulls from recycling, or some other bottom-of-the-barrel operation that might have paid $1 for all the scrap. The experienced buyer sees that they don't have any particular rhyme or reason behind what they sell; and it all appears to be scrap. They know to stay away.ManufacturersIt depends.Almost every engineer will have a handful of companies on their own blacklist. You will often find that many of them are highly reputable companies, too. At some point, the designer will have chosen to use a brand's part, either it looked good, or worked well in early prototypes, or something along those lines. Then some timed event, either come purchasing, production, or long after its been in the field, there is some failure. Sometimes they didn't read the datasheet and missed something. Sometimes the silicon lot has a terrible defect in it and an entire lot snuck by probe or test because of an idiotic hardware fault. Sometimes there is a design oversight and the part is put into a particularly stressed condition. Whatever it is, this part is now a problem for the engineer and it comes down to the experience they have with the vendor as they work to resolve it. If the vendor is good, and they get it fixed, they react one way. If the vendor is good, and they cannot fix it, they react another. If the vendor ignores them because they're a Tier 3 or some other name of a small guy, and they get no where on useless forums or similar places, they feel scorned and never use another part from that vendor. Monetary impact has a huge role in it, too.In a recent design I did, I needed a simple buck-mode switcher. I used a part from a company with 3 letters abbreviation, used their calculator tool, got some numbers, and did a prototype. It essentially smoked. It "powered up" to 1.02V unloaded, and nothing under load and the part got very hot (eventually reflowing its own solder). Everything within the calculator's specs, and same parts as it commanded. Nothing. I could have monkeyed with it for ages, but I decided to discard the supply, verify everything else (which worked just fine) and did a redesign with another switcher made by another 3-letter-abbreviated company who happens to make a popular spice tool. Boom, another turn of prototype PCBs, which included a few minor changes to the design in addition to this new Switcher.Nothing.It would not power up at all. All of the nodes had the right supplies. Everything matched the datasheet (canned circuit right off of page 1). Just... nothing. I shot this company a tech support inquiry on their webpage and on their twitter. After 3 days, nothing. I moved on to another popular vendor, who only has two initials. The lowest cost solution of them all. The fewest parts of them all, too. I simply take a hit for inductor size (lower switching freq) and lower input rail (18V instead of 20 or 24V). A third round of boards. Power it up... and...It works. Perfectly.So now I personally have a preferred vendor of switching supplies, because of whom I had success with. I will then bet you that I can find an engineer who had the exact opposite experience I had, and exclusively uses another vendor. But note, I don't automatically excludeallof the parts made by other companies; but specific lines of products which seem to have inferior support models.It'll be the same thing with passives, and discretes.The fundamental value you get with a distributor like Mouser or Digikey, is that if a part fails its advertised claim, you can call them up and they'll ship you a replacement, and likely chase down the manufacturer to deal with the bad material.