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Old 5th Dec 2016, 9:47 am   #61
MrBungle
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Default Re: R.F. voltmeter: your thoughts, please

That also applies to vendors such as Diotec and Taiwan Semiconductor I found who are sold retail in the UK.

RS/Farnell major brands only.
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Old 5th Dec 2016, 3:24 pm   #62
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Default Re: R.F. voltmeter: your thoughts, please

I don't buy that much from China, but so far I've done OK, as per Terry in #17. I always look for a minimum feedback score of 99%, preferably 99.5%. If they work at 146MHz, I'm happy.

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Old 16th Dec 2016, 2:49 pm   #63
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Default Re: R.F. voltmeter: your thoughts, please

I think the fake semiconductor issue raised in this thread is worth of an entire discussion. I was sent some TO-5 devices from a supposed reputable American semiconductor source. They were supposed to be JFets in a TO-5 case (made by siliconix or Teledyne) and the degree of fraud was astonishing. They were nothing more than some generic NPN transistor, with short leads, but new long leads had been welded to the old ones (a diagonal cut welded together) and I could break the joins. Then the leads and the whole transistor body was fresh Tin plated, with new writing screened on. The also had Korea stamped in to to body. Later I found out that there was a transistor equivalents list that wrongly listed the type number of the Fet as an NPN transistor, presumably the fakers were using that and were clueless that the part I ordered was a JFet, which is how this time they got caught out. Also recently a friend had a pcb assembly made in Asia, and one of the surface mount diodes was a fake as it had no label and a thin package, it then became impossible to perform a reliability analysis because the pcb contained a part with unknown parameters.
What happens when these fakes get into automotive and avionics and military supply chains, total disaster. It really needs to be stamped out or have severe penalties for those doing it.

Last edited by Argus25; 16th Dec 2016 at 2:58 pm. Reason: Bad spelling
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Old 16th Dec 2016, 3:06 pm   #64
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Default Re: Warning fake components

Fakes have been reportedly found in military, aviation and hospital life-support equipment.
Even major structural parts of airliners have been found to have been faked.

I don't suppose they cared much what your TO-5 device was supposed to be, just so long as the case looks right enough and the writing they put on it says the right part number.

I got bitten 15 yers ago with some posh Analog Devices RF opamps. Someone had got some ordinary cheap parts in the same package style, polished off the writing, and screened on new. The part bore no resemblance to what it purported to be, and they turned up in the material flow of one of the world's largest contract assembly firms.

Usually, nowadays they try to get something that one of the little semiconductor checkers says is the right polarity because that will pass further down the chai before it gets spotted.

I'm probably more worried than most people, but my day job is designing avionics....

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Old 18th Dec 2016, 1:44 pm   #65
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Default Re: Warning fake components

I'm inclined to agree with the remarks made by Radio Wrangler. I'm very concerned about fake silicon and cheap parts out of the far East. An IC I have received from there in fake form is the MC3334 ignition controller IC. It is getting hard to find the original Motorola part, many/most are fakes now. Plus the remarks on other posts about the 2N3055, which I agree has to be the most faked transistor in human history. Luckily I located some genuine 1970's vintage RCA ones, which are the only ones I now trust. After the mid 1980's the fakes came "online" and its only getting worse. Tragically, the TO-3 case is becoming obsolete, it is a shame, as it is thermally superior to a plastic cased transistor in most instances, its just it doesn't suit surface mount.
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Old 18th Dec 2016, 2:00 pm   #66
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Default Re: Warning fake components

More on fake IC's, I thought I could also mention how the MC3334 IC, when first introduced into Delco HEI ignition modules was just a bare die mounted on a ceramic substrate, coated in clear gel inside the module. It wasn't actually sold for about the first 5 years as a discrete IC. Later it got put into a plastic 8 pin SOIC package by Motorola, once that happened it got cloned asap. I guess it was protected that way initially from cloning. New replacement modules have the SOIC IC on a standard pcb. I was able to photograph the die under a binocular microscope and the new and old modules attached.
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Old 18th Dec 2016, 3:24 pm   #67
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Default Re: Warning fake components

A little bit on from the other side, but I used to work for a company (some considerable years ago) that serviced VCRs's. The service manager used to return heads under warrenty from earlier machines, working on the presumption that the person who opened the package at the other end was not the same person who packaged the replacement item (and obviously both were unskilled). This worked for some considerable time and saved the company I was working for hundreds of pounds. It does make me wonder what checks are performed on reception of components, even by companies which produce safety critical items..
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Old 18th Dec 2016, 5:21 pm   #68
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Default Re: Warning fake components

I once tried to get a Hitachi alternator apart and managed to crack the end casting. It was the Izozo one with the brake pump on the brush end.
I hid the crack good enough to part exchange it.
The brake pipe connector was not present on the replacement unit so the guy at the parts counter got further distracted by me borrowing a spanner to change it over.
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Old 18th Dec 2016, 5:51 pm   #69
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Default Re: Warning fake components

Quote:
That also applies to vendors such as Diotec and Taiwan Semiconductor I found who are sold retail in the UK
I'm not sure if I misunderstood but both Diotec and Taiwan Semi are very reputable manufacturers. Diotec have a had a few product recalls particularly some out of spec BA159 diodes but these days are pretty fault free as a subsidiary of Semikron. Taiwan Semiconductor are one of the largest semi manufacturers in the world and often contract-manufacture for the well-known western brands.

But you can fake any logo.
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Old 19th Dec 2016, 6:00 pm   #70
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Default Re: Warning fake components

Having been caught out a number of times with fake parts and hundreds of hours wasted investigating weird circuit operation, I now only source stock from distributors with traceability back to the manufacturers.

One case I recall was a Sony AE2B chassis when it came into the workshop after a customer had tried to re-solder the many, many dry joints by wetting the board with liquid flux of the type used for surface mount repairs! While this helped with solderability, the surplus was left in situ and created a nice leakage path for high voltage to cause havoc. It did, and promptly went BANG when the customer switched on taking out the 2SC4927 line output transistor. That is when he thought, I know Rich will be able to...

As I did not have these in stock, after cleaning up and making good damaged sections, the set was temporarily tested with a handy BU2525AF and a BY223 as a damper diode which normally is integral in 2SC4927. The set powered up and worked fine, good, time to order some replacements.

Replacements sourced (from a known supplier) looked almost identical to the original with Hitachi logo, except the printing was a little smudged and plastic case was slightly lighter in colour. Fitted, switched on and after three seconds the transistor went into thermo nuclear meltdown. Hmmm refitted BU2525 and set still worked OK. Checked the remaining 2SC4927, none had the built in damper diode and when I sourced a good device from a scrap chassis to check other subtleties, the gain was far too high.

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Old 23rd Dec 2016, 11:26 pm   #71
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Default Re: R.F. voltmeter: your thoughts, please

Quote:
Originally Posted by Craig Sawyers View Post
As MrBungle said - it is a real lottery buying silicon from oriental sources.
With the emphasis on con for those fake semiconductors!

Symon.
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Old 23rd Dec 2016, 11:50 pm   #72
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Default Re: Warning fake components

Quote:
Originally Posted by McMurdo View Post
I'm not sure if I misunderstood but both Diotec and Taiwan Semi are very reputable manufacturers. Diotec have a had a few product recalls particularly some out of spec BA159 diodes but these days are pretty fault free as a subsidiary of Semikron. Taiwan Semiconductor are one of the largest semi manufacturers in the world and often contract-manufacture for the well-known western brands.
I had a batch of Diotec BC547C's from Rapid which were out of spec hFe and low transition frequency. Also Taiwan Semi 78L05's out of voltage spec. I'm not a heavy sampler of parts but if I buy ten of something and two or more are out of spec then that's a bad batch with poor QA.

It's not about the manufacturer specifically but the QA process after manufacture and the supply chain.
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