Being a hoarder, I still have stocks of these and other vintage components in my workshop, and maybe you do too. I keep them mainly for repair purposes and would not set out today to build a design using 40-year-old components unless I was feeling more perverse than normal.
No lack of bias
Then I read an article about component obsolescence in another electronics publication and the thought struck me, how easy would it be to build projects from old issues of this magazine? I just happen to have issue 1 of Practical Electronics (November 1964) and to demonstrate a lack of bias, also of its younger contemporary, Elektor (December 1974). A glance at the designs of 1964 shows up a lot of transistors we don't use today: the 2G102, MAT101, loads of OC71s and a few OC171 devices. I don't think you'd find any of these at a current electronics store. Get back into the time machine.
Moving forward a decade, our Dutch friends were using mainly TUNs and TUPs, transistors that I had forgotten entirely until now. TUN and TUP stood for transistor, universal, NPN and transistor, universal, PNP. Accompanying them were DUG and DUS, the diode universal germanium and diode universal silicon.
The whole idea was to simplify sourcing of semiconductors by making circuit designs compatible with as many devices as possible, all listed in tables. Effectively, a TUN was a BC107/108/109 equivalent and the TUP was anything that behaved like a BC177/178/179. TTL logic of the 7400 variety took its place now, as well as more exotic ICs such as the 741 op amp and the MM5314 clock display driver.
These were pretty simple times, when you could almost see what each component did in a circuit. Even now, you would not have too much difficulty in sourcing at least 50 per cent of the semiconductors required. Maybe it was the golden era of simple hobby electronics, but that's debatable. What's not in dispute is that soon afterwards discrete components were becoming replaced by integrated circuits of increasing complexity and levels of integration and it's these 'big chips' that are proving very hard to find nowadays.
Component obsolescence
Which brings us conveniently is what the industry calls 'component obsolescence'. This does not refer to the ageing property of some components, although it's a fact that over time some germanium transistors selfdestruct through dendritic growth; plasticcased ICs become unusable through moisture absorption and low-value polystyrene capacitors 'dry out' and go open circuit.
What it actually means is when you order some perfectly straightforward component your supplier says it has been discontinued. 'Rubbish', you think and then discover that not only have Maplin and Rapid dropped it, Farnell and RS no longer list it either. You do a Google search and find not only is the nearest supplier on the other side of the world, but they ship only by DHL and don't deal in less than 100-off.
Someone who knows all about component obsolescence is Phil Innes, chairman of the Electronics Manufacturing Services Association. In a blog on Components In Electronics he states the problem is getting worse, thanks to a greater choice of new components and shortening life-cycles. Manufacturers don't want to take chances producing vast quantities of components they may not sell, while distributors cannot afford to warehouse parts that sell only in dribs and drabs.
Volume customers
It gets even trickier when you're dealing with highly function-specific ICs that are only used in niche markets. In cases like this, the semiconductor manufacturers approach their volume customers and ask how many tens of thousands they intend buying over the coming 12 months. They then aggregate these numbers and produce enough to satisfy this demand. If there's insufficient call for an existing product (which often happens when a superior replacement comes onto the market), they may well kill it altogether. Residual stocks remain in the supply chain for a while, particularly with distributors, but they dry up eventually.
"So what happens when, for whatever reason, you've missed the last time buy deadline?" asks Innes. An obvious solution, he states, is to find a different part with the same form, fit and function (dust off your equivalents book!). Lucky breaks of this kind don't happen that often and then the next step is to look outside the normal channels of supply for the original part that you really wanted. Innes continues, "As a general rule, anything that becomes scarce becomes more expensive and electronic components obey this rule perfectly!"
Penny numbers
So where do you look now? Google is your first call for these obsolete and end-of-life parts, as you may just find a distributor able to supply the numbers you require. If you are looking for more than just penny numbers then it's worth contacting a component broker. Brokers work on a no win, no fee basis, although their commission is not charged separately, but incorporated in the price you pay for the parts.
I have dealt with a very effective firm by the name of Ashlea Components of Swindon, who have been in this rather specialist business since 1987. They have developed relationships with suppliers worldwide and use their knowledge of the market to source items that you might never find.
But what if your need for, say, obscure unijunction transistors is only a couple? Brokers won't be interested, so instead you approach a dealer. Although few of them advertise, there are a dozen or so dealers in the UK who specialise in impossibleto- find semiconductors and valves. Transparent TRRAMs
I suppose valves were the original transparent components, followed by the OC71 when you scraped the black paint off the case to turn it into a phototransistor. But the next big thing is transparent ICs, according to press reports. Researchers in Korea have developed a transparent resistive random access memory chip, which they have dubbed TTRAM.
It is claimed that TTRAM chips are cheap and easy to make, which is why transparent memory chips may appear in all-clear mobile phones and other personal devices within three or four years' time. Alternatively, the technology could stimulate development of clear computer and TV screens, embedded in glass or transparent plastic. Whether this comes to pass is another matter, but there have previously been fashions for crystal clear landline phones and the original Swatch mobile (remember it?) was fashioned in a quite alluring shade of translucent pale blue plastic.
Baitron is one-stop sourcing service provider for ICs, connectors, discretes, transistors and other components and devices. Baitron offers a highly reliable supply source for hard to find, obsolete and long lead time components, as well as a competitive source of cost saving on current available components. Article Source: |
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