I need a new NEC N8700 (Speed Control Transistor/Triac) for my grandson’s Radio Shack RC Car. Trying to find the same thing or a suitable substitute. Thanks
Hi @rvseverson, welcome to the forum.
I’m not finding any technical data on the N8700 other than it’s a transistor in a TO-220 package. Do you know any electrical specs on this? If you have a datasheet on the N8700 I can check if we have a cross to offer.
Thanks,
Lindsay
Lindsay Foy
Senior Applications Engineer Technician
DigiKey Electronics
Yeah. That’s my problem too. Appears to be an old NEC variable output to drive the motor in an RC car. Found this on internet; https://modelisme-buggy-vintage.com/epages/329b65de-5b3f-453b-b4e2-67465aba5323.mobile/fr_FR/?ObjectPath=/Shops/329b65de-5b3f-453b-b4e2-67465aba5323/Products/N8700&Locale=fr_FR
That was the same sort of information I was finding as well. The bad news is that without some general specs it’s sort of a guessing game as to what it could be or how it operates. I have almost 6,000 options in a TO-220 footprint (you can see them here: Electronic Components and Parts Search | DigiKey Electronics
If anyone comes up with some specifications to add to this post it’d help narrow down the list to something that would work in the N8700’s place.
Best guess is that it’s some sort of NPN BJT or N-channel FET; these are the most likely devices used for speed control in small DC applications, with the BJT becoming more probable as the age of the device in question increases. FETs capable of significant power handling are a relatively new thing.
Doing some reverse-engineering to figure out the basic structure of the circuit would offer clues. One pin on the transistor is likely connected to the controlled load, the other to one of the main supply rails. If it’s between the load and the negative rail, it’s likely an N-type device. If between load and positive, P-type is likely. The third pin is likely connected to some sort of control IC, possibly through a resistor of some type. If that resistor has a value in the tens of ohms or higher, it’s likely a BJT. If it’s a low-or non-existent resistance value, it’s more likely a FET.
The good news here is that TO-220 packaged transistors aren’t usually something super-exotic or special; if one can ascertain its basic functional identity, selection of something in that same basic family has a fair chance of giving a reasonable result.
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I’m going to guess that’s a FET of some sort, and take a wild guess that one of these might possibly do the trick. No guarantees, but it’s not a huge loss if it doesn’t pan out.
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Installed the 80A version and it’s working great! Thanks for the help.
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rvseverson contact me by email (removed for privacy) & I may be able to help
The problem was solved with the response prior to my “Thanks for the help”. Thanks for the offer.
rvseverson ho il tuo stesso problema, gentilmente potresti inviarmi un link dove hai acquistato il tuo transistor 80A ?
non trovo nessuna informazione riguardo Nec N8700.
molte grazie.
salve Rick, ho lo stesso problema di rvseverson ma non riesco a leggere i tuoi transistor allegati… gentilmente potresti rimandarli? grazie.
Hello @Simon49,
Rick suggested part TK4R3E06PLS1X-ND or part TK4R3A06PLS4X-ND which are both 80A parts as mentioned. They are both currently available on the DigiKey website.
-Robert
Thank you very much, Robert!!! Now i can see the right code of Mosfet 
Indeed, it is a MOSFET. There is no information about it anywhere, at least that I can find. I have a couple of those because I used to work in a Radio Shack service center around 20 years ago.
I see that you solved the problem. But for the others asking, you will be better off, buying a more robust replacement like the other user did. The only thing to care about are the same as always, the Drain continuos current rating, the voltage rating (not an issue, as you are working with 7+ volts), the “On” Drain-Source resistance, and probably, the gate threshold voltage, because you are working with low voltages. But modern parts often outperform these old parts, so there is a chance to get a better working part nowadays.
Here I included a picture of what this cheap component tester that I have revealed about it 
