I have a circuit board (Japanese from the '70s) which has three small rectifier diodes. These are small (4mm x 3mm) football shaped objects in white ceramic packaging with the cathode end coloured black. The leads are about the same diameter as the 1N4000 series rectifiers. Regretably there is no other markings on them. Does anyone have any idea what I could reasonably expect for Imax and Vr?
Ted
They used to make 1N400x type diodes with that kind of construction. You can probably substitute 1N4007s unless the PCB is discolo[u]red under them from long-term overheating. I think they were rated at 1A or 1.5A, no more.
Higher current diodes (eg. the 3A 1N5407) are not particularly expensive but are physically much larger.
You can probably also infer from the circuit and application what the voltage should be. For example, if it's a 120VAC-input motor speed control, a 1N4005 is probably good enough.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
I've seen that style of construction too. Forget the part numbers but possibly a Pro-Electron designated part.
Something like this ?
That's a fast diode btw and 2A.
Graham
Thanks for the quick reply, Spehro.
The board is from a snowmobile engine tachometer. It used the lighting coil AC frequency for determining rpm. In the snowmobile, there was lights and an AC "regulator" (of unknown provenance) to keep the voltage down. In the current application (a homebuilt aircraft) there are no lights or regulator. Max voltage out of the coil is around 40 0r 50 volts peak. These diodes will probably be ok but I guess I better set up a test circuit and run the voltage up until I see the first signs of break down. Every thing else in this circuit is OK at this higher voltage.
Ted
Thanks Pooh Bear, that's the package all right. Since there's no visible markings, I'll just have to maeasure the Vbr.
Ted
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