Hard to Find or Unobtanium Semiconductors

[W1RKW]

FYI:  Anyone looking for hard to find or almost unobtanium semiconductors should go to American Micro Semiconductor.  I have found several hard find parts here. And prices are reasonable too.   

[W2JBL]

     Buyer Beware:I bought 6 each of  2SC1969, 2SC1306 and 2SC1307 from them to replace the finals in some vintage CB radios and none of them worked. They all tested good on an ohmeter but did not work for RF. Chinese counterfit junk. They claimed the devices were all tested good (BS!) but they did not work at RF and I destroyed part of the board of my ancient 148GTL by repeatedly changing them out until I figured out I had been had. Amazon.com did not make good on my complaint and the seller denied any responsibility.   

[KB2WIG]

I've used the following...

Mouser,  RF Farts,  DigiKey, Allied, Dan's small parts

At least they are in the USA. ePay is a gamble. 

Here in sorryexcuse,     Stewart W. Smith.......   


klc

[WBear2GCR]

Chinese counterfeits are a BIG problem. BIG.

Very difficult to know... one has to test parts before using.
Aka = trouble.

It's incredibly ironic to me that it is now easier to find ancient vacuum tubes than to find a very very
wide range of semiconductors. Amazing.

If you can buy a piece of used gear with old parts, in general, ur on safer ground.

[Opcom]

A reputable reseller -always- has paperwork tracing the parts back to the original manufacturer.
These would always be resellers/distributors that are authorized by the manufacturer.
This is the only situation in which there is any recourse.
It is the practice in the semiconductor manufacturing industry to warn customers never to buy from anyone other than an authorized distributor or dealer.
A list of authorized distributors can be fond on the manufacturer's web site.
If the part is no longer stocked locally, an authorized distributor has the means to see, through the computer systems, which other authorized distributor may have it.
They may not be able to cover expenses doing this for a 5-10 piece order and that is why some uncommon or obsolete $5 parts cost $50 or more, each, when bought through proper channels. But you get the genuine item.

This happens in larger circles and it is not always counterfeit parts.

Some years ago, a Chinese telecom company wanted to buy ADSL modem chips to build modems for its own customers. They did not want to pay a regular price but also did not need the highest performance, and no one was making low-performance ADSL chips for obvious reasons.

The sale was made possible by 'adjusting' the parts in the factory using a laser so that the performance-price point was achieved and millions of them were made for the Chinese telecom company and everyone was happy.

After some time, a few tens of thousands of these parts showed up surplus at a random Chinese reseller. The part number on the part was the same as the high performance global version but it had another marking, which was only of interest to the semiconductor manufacturer to indicate the customized parts.

A USA customer, the modem company, presuming to go around the USA distribution network and 'carve the fat out of the middleman', bought up all of the special ICs for pennies on the dollar and had the modems made, quietly merging the special parts into the production stream. The modems were made China by a contract manufacturer of course, so there was no inconvenience and they were and shipped. I am sure the modem company's buyer had in mind getting a big bonus for such a money-saving coup.

The performance result was as expected when the wrong parts are used, and the customer, the modem company, complained to the manufacturer of the ICs. The IC manufacturer tested some sample modems, and was at first confused by the trouble, and then examined the ICs the modem maker had used, and found that they were not the ones sold by authorized regional distributors but the 'special' ones not made for the global market and licensed only for the Chinese telecom company. This was confirmed by X-ray of the dice and images were shared, all very transparently. The Chinese reseller correctly stated that it had delivered exactly what had been ordered and refused liability.

All of the claims were denied and it cost the greedy modem manufacturer hundreds of thousands of dollars to have all of the modems reworked. In China by the contract manufacturer, of course.

Who was the winner of this? Several companies made money, but not the right one! That is the big money lesson about sourcing parts.

[W1DAN]

Folks:

This is indeed a big issue and legislation to guard against this is being drafted. Here is an excellent paper on the subject:

http://www.hq.nasa.gov/office/codeq/trismac/apr08/day2/hughitt_NASA_HQ.pdf

I have also seen foreign companies purchasing the entire stock of a manufacturers product that is end of life. To keep my hobby going, I have stocked up on a few parts when EOL is published.

Dan

[W1AEX]

I have read that there are also "attractively priced" counterfeit Chinese replacements for common RF devices like the popular MRF-150. They look like the real thing but more often than not they melt down and take out other components along the way as Chris JBL mentioned. I guess it's a good idea to stick with trusted vendors instead of taking a chance on unknown vendors selling parts made with chinesium.

[W1RKW]

Counterfeit semi's are a legit concern.

I've ordered from AMS maybe 2 or 3 times over the last couple of years and the parts worked. That's all I can say. Don't know if they were counterfeit or not. Probably could have been but at the time didn't even consider thinking about it.  But a good point to consider even for consumer grade junk.

Conversely, I have ordered many RF power devices that are considered obsolete yet available from a so called reputable source that many here may frequent and on 2 occasions had faulty devices out of the box, same batch and supposedly tested and expensive.

It's a crap shoot.

[WD5JKO]

   For work we use some expensive RF transistors, and when ordered from a US distributor, and from a US semiconductor company, I got a series of date codes that were trash..infant failures were the norm. After about 6 months of back and forth with an application for that company, they finally fessed up, and agreed to replace my entire stock, no charge. Still, I went through a lot of pain and suffering second guessing myself. Seems their wafer fabrication center went from a Korean fab to a Japanese fab, and the process shifted. Then the packaging plant in Malaysia screwed up with the bonding wires. So much for outsourcing, and cost cutting. MAGA. 

   I have also ordered discontinued parts from a Chinese Ebay seller, and they are a virtual clone of the real thing. One item is a 1700V PIV 30A 3 phase bridge rectifier. I've used about 20 of them thus far, and have been 100% successful!

Jim
Wd5JKO