I needed several 74LSxx variety ICs for a board repair. I was surprised to discover the DIP packages were out of stock at Mouser and Digikey! Factory backorders, and they are not stocking huge quantities as they did the past. Jameco had them in stock.

I'm also noticing the supply of MRF-150A devices are also slowly fading from view

"Trough hole" packaged parts are no longer used in the industry and were all replaced by SMD devices. Demand has collapsed and suppliers have adapted their stocks accordingly and/or stopped manufacturing these parts. Nearly ALL "through hole" electronic parts are now considered as "obsolete" and supply will dwindling in the years to come. Also, 74xxxx series logic chips are considered as "prehistoric" parts and won't be remanufactured again. There should be still millions of these in dormant stocks at various parts suppliers warehouses but since there's is no demand and turnover is very low they'll very likely end up scrapped one day.

I agree. They are not "scarce," they are just in the wrong places.

If you can find the SMD equivalent, you can always use an adapter board and "Molex" pins to make a workable DIP.

I had to make my own boards to convert 10mm IF transformers to fit on a 2.54mm spaced proto board.

https://antiqueradios.com/forums/viewto ... 9&t=390262



https://media.digikey.com/Photos/Aries/LCQT-SOIC8-8.JPG

Rich

Another option is SMD to thru hole socket adapters like this one.

https://www.mouser.com/ProductDetail/Ar ... CsQAvD_BwE


They also make solderless ones.

I'd be substituting 74HCTxxx parts. Much newer, lower power and still available.

They will work except when use with R/C delays (analog circuits.)

As an engineer, I stopped using 74LSxxx in the early '80s. HCT took over very fast at the time.

There are hundreds of thousands of semiconductors that were once popular but are now obsolete, forgotten, and unavailable except through surplus channels. 74LS small scale logic chips in DIP had their day and for the most part are following the pattern towards oblivion. 74LS02 in DIP is probably seldom used if at all in new designs, but if you just need a few to keep a piece of gear going it appears there are still tons of them for sale on eBay.

try rochester electronics $3

https://www.rocelec.com/search?q=74ls02

Thanks Peter. I never heard of them and I just bookmarked them.

What about looking at ebay?

https://www.ebay.com/itm/161227039623?h ... SwLh9hCHEI

Peter,

I have:

2 74LS02,
2 74ALS02,
1 74F02, and
15 74HCT02 ICs.

You can have any, or all, of them for postage.

All plastic DIP. I have no need for them. Bought & used them decades ago. These are just leftovers. PM me, if interested.

Surface mount sales, exceeded "through hole" sales ~1995. That's more than a quarter century, now. In addition to that, 3.3V logic replaced 5V logic, too, many years ago.

The only old logic family, that's still got some use is 4000 series CMOS, mostly because of it versatility. It can operate with supplies ranging from 3V to 18V.

When it comes to most logic circuits, programmable logic (PLDs to FPGAs) has mostly supplanted fixed logic in most areas. With existing logic, whole bus buffers, are used more than gate packages. Also a lot of custom chips, if the production volume justifies it.

Yeah.. they specialize in maintaining a supply of discontinued or hard to find semiconductors.. and they are an authorized distributor.

I received some fake/counterfiet OP-275 op-amps via some Asian ebay seller ... who actually admitted they were fake and refunded me.
I only determined they were fake when the current draw per chip was twice that specified on the Analog Devices datasheet.
I contacted Analog Devices. who makes the op-275, to ask if there was any foolproof way of detecting fakes.
The sales rep told me that counterfiets were the biggest problem in the industry and the only/best way to avod them is by ONLY purchasing from authorized distributors like Newark, Digikey, Mouser etc. And from other trusted authorized resellers such as Rochester !

That's how I found them.

Nasco is another broker we use at work. They have some fancy x-ray technology that allows them to examine the dies inside the device to detect counterfeits. We have great results with them on obsolete chips (but they aren't cheap)

Thanks for the offers, but as I mentioned Jameco had a large supply of them for a decent price. What was surprising is that all of the other 74L$xx devices were in stock and available and just the LS02 chips were backordered. I'd rather not buy semiconductors on eBay since most of them come from China despite the seller's shown location. The radio is a JRC transmitter and I'd rather keep it original since it is a fairly scarce transmitter.

https://www.jameco.com/z/74LS02-Major-Brands-IC-74LS02-QUAD-2-INPUT-POSITIVE-NOR-GATE_46287.html

It's interesting that Jameco's illustration for the 74LS02 they are selling shows a 8506 date code. That might be just what you get, too. It's safe to say that Motorola doesn't make those new any more.

Ted

Some of the parts Jameco sells are pulls out of boards. Others are old stock. Ordered some one-time programmable chips and they were already programmed. Like buying used flashbulbs.

Their printed catalogs used to show the catalog number for used parts or old stock in a different color. Seems they now just show them as "various manufacturers".

Used to use Jameco a lot and still like them for some things but I wish they were more transparent.

Exactly. Once burned, fuse type PROM's can't be erased or re-programmed. Pullouts are useless.

If the goal is to keep a vintage transmitter on the air, you may be better off with a NOS or good used "pull" device, rather than a freshly manufactured one anyway. Not for nothing, the masks, production machines and in some cases whole factories that made those chips 25, 35, or 45 years ago simply don't exist any more. Where the chips are still produced they are done with today's processes and equipment, using masks and materials suitable for today's production. So even though the part numbers are the same, the chips themselves probably are not. Unless you have compared the data sheets for the old chip to the new one, it is possible that there could be subtle differences in timing or voltage levels that can get you into trouble. A new chip that switches ten times faster than the old one is not necessarily an advantage if the latency was necessary to keep the board from latching up.

Well what did we do when the drugstore and Radio Shack stopped selling tubes? They are still out there, not where they used to be.

The old chips and germanium transistors are out there; I found the obsolete Motorola ECL chip that I needed for my Heathkit AJ-1510 on Ebay. Wasn't cheap, but whaddaya gonna do...

The worst chip I ever tried to locate was a 74S90N. They were made for an extremely short run. I wanted one for a homebrew frequency counter since it was about the fastest decade counter at the time... I don't see anyone selling them.