ECG, NTE, and SK are lines of universal replacement semiconductors. The underlying concept is that each ECG, NTE, or SK numbered device can replace a group of other semiconductors. For example, the single most popular ECG and NTE transistor, the 123AP, replaces thousands of different OEM and industry standard (JEDEC) part numbered transistors. When the Delco DTS line of power transistors were discontinued, SIE began using the ECG165 in their 300 volt downhole power supplies (the later schematics actually call for the ECG165). The universal replacement folks have always encouraged the use of their devices in new designs, but the relatively high cost of these devices has limited the practice.
ECG and NTE use the same device numbering system, but the SK numbering system is completely different. Each company has traditionally published its own thick printed replacement guide or cross reference, and more recently computer software (the replacement guides and software also cross-reference each others part numbers). Make friends with a counter worker at your local parts house to get a free printed book (otherwise they charge a few bucks for them). The NTE software can be downloaded on this NTE page. The ECG software is no longer available for download from ECG following the acquisition of ECG by NTE. The SK software does not appear to be available for download directly from TCE SK. We have seen the SK software for sale, but it is an old DOS program hardly worth the trouble. Check out Moyer Electronics for online versions of the NTE, ECG, and SK replacement guides, as well as free downloadable versions of the software. There is an advantage to having more than one cross reference as we have actually found a few mistakes over the years by checking more than one book.
ECG was started by Sylvania in 1966, and was more recently acquired by Philips. ECG offered vacuum tubes as part of their line until that market dried up. NTE is a privately held domestic corporation started in 1979. SK was started by RCA, and was more recently acquired by Thomson Consumer Electronics (TCE), who already had a replacement line. Other manufacturers had replacement lines in the past, including Motorola with their "HEP" series, General Electric with their "GE" series, Raytheon, Mallory, Sprague, and Workman. Even Radio Shack dabbles in the replacement semiconductor marketplace, but their cross reference book is thin by comparison to the major players (RadioShack.com offers NTE / ECG devices also). In addition, several electronics suppliers have established house replacement lines, like TCG and EXR, but most of these were/are small incursions, tackling only the top 100 or so replacement devices.
TCE has done very little with the SK line since acquiring it, except for renaming it the TCE SK Series. They have never even established a website, nor have they produced a recent cross reference book. As of January 19, 2001, NTE acquired the assets of ECG, and it seems inevitable that NTE will now dominate the replacement semiconductor marketplace. The numbering scheme used by ECG, and later copied by NTE, had already become the accepted default long before the acquisition of ECG by NTE.
AnaLog Services, Inc. files its stock of transistors by their ECG / NTE cross numbers with both a
forward index and a
reverse index. This simplifies locating transistors when they are needed and can suggest a replacement part when necessary. However, this latter procedure must be used with caution because a given ECG / NTE number will replace many devices, but not all devices in the replacement list can replace each other. This is true because the ECG / NTE devices are intentionally selected to replace a group of components with the same or lesser parameters. AnaLog Services, Inc. avoids the use of these universal replacement devices whenever possible; we almost always have an exact replacement part in stock (and ECG, NTE, and SK replacements are usually more expensive than the original part).
Follow these general rules for substitution to stay out of trouble:
Use a device with equal or greater breakdown voltage,
Use a device with equal or greater operating current,
Use a device with equal or greater power dissipation,
Use a device with equal or greater gain bandwidth product,
Use a device with equal or lower switching time,
Use a device with equal or lower trigger current,
Use a device with equal or lower reverse current.