Chip finder?

Do a search for the nte replacement guide, it's a line of "universal" components with a cross-reference.

Though, as I was reminded recently when I looked for something for someone, the guides fail if the devices are too old. After a while older devices are dropped and the cross-references dropped too. So you can't even use the cross-reference for it's most important use, getting some basic information on a device.

Just try websearches on old devices, sometimes you can find pages that give information. Go to amateur radio club fleamarkets and buy old databooks (usually they go cheap), and become more definitive sources of information than second hand sources. They can often be useful in themselves, since a lot of secondary books pull information from manufacturer's databooks.

Of course, the components that can be directly replaced use standard numbers, though sometimes the prefixes or suffixes vary from manufacturer. A PN2222 is basically the same as a 2N2222, for instance, with the former having a plastic case and you should be careful if the device is used close to its power limits. On the other hand, once you grasp this about prefixes, a good but not consistent rule, you should be able to find data about common devices. Likewise, op-amps tend to have standard pinout and multiple sources (though again different prefixes), and for a lot of general work a handful of op-amps will serve the purpose. Of course, you do need to know when an esoteric op-amp is specified, since there usually is a good reason why someone specified it. The logic families are pretty standard, too.

Of course, it helps to know why specific parts are used. Sometimes there are really good reasons, but for hobby purposes it's often a case of either using things that are commonly available (which means a small number of devices get a lot of use), or specifying a part that can easily be had. I remember being fourteen and someone at high school spending lots of money on a replacement line op-amp, and when I said it was a common op-amp and lots of other ICs could be used there, he said "I don't want to make any errors". The article specified the replacement line part since chances were good one could get it locally, the device it replaced was just as good or better.

The more integrated an IC is, or the more specific its intended purpose was, the harder it will be to find a direct replacement. Unless there is a second source of the device, there at best will be functional equivalents, that may require changes in pinouts or external components, or even a complete redesign because the alternative is just sort of like the original. More recent and fancy ICs, chances are good that unless you can get the device, you need to look at some other circuit, since there will be no easy way to use an altnerative.

The more you know about electronics, the easier it is to sort things out.

And sometimes if the circuit is too old, there is no real point in using it, unless you actually have the parts on hand. Take just about anything, and it's been written about numerous times, and if the devices are hard to get, then a more recent schematic that does the same thing is likely quite available, using still available devices. More recent circuits may be better anyway, because an old circuit would mean not just finding one hard to find device, but then you discover you need that coil that's no longer being made, and the circuit doesn't really say much about it other than the part number, so you're stuck there too.

Michael

The Universe is pounding on your door trying to tell you this is a bad idea and you won't acknowledge it. Just because you found someone's circuit from 1975 that says it will do what you want doesn't make that the best plan to pursue.

There is a reason that projects using Coherers or Audions are considered deprecated notions. It's the same with obsolete integrated circuits.

Put your efforts into finding a more recent implementation of the idea or post about what you are trying to accomplish and ask for help with that.

The nte site has one, but I wouldn't buy their parts, since they are so expensive.

Regards, Bob Monsen

NTE is for lazy folk who don't bother to compare datasheets and instead want someone else to do it for them and just sell them the damn part. Prices usually reflect Quantity 1 retail not catalog pricing with min order rules.

Just google the part numbers directly without using a cross ref, find out the basic function and DC parameters and pinout from a datasheet then try to find a part using a search tool from a catalog like DigiKey or Mouser for example.

Thanks for all the help and info. I will try the ideas posted. Thanks again.

Sky King