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SM diode marking woes.

I'm noticing that some circuit boards I'm repairing have SM diodes marked with the old General Semiconductor logo and the letters "SJ" or "S3". These diodes have bodies about 4mm long.

I'm pretty sure "S3" is SS23, a 2A 30V DO-214AA (4mm) diode.

But according to Vishay (which bought out General Semiconductor), marking code "SJ" means S3J, which is a 3A 600V DO-214AB (7mm) diode. And yet the part on the board is 4mm, not 7mm. The Vishay data sheet doesn't say anything about alternate packages.

So I wonder why the discrepancy? Did Vishay change General Semiconductor's marking codes? Or did they just change the package of the S3J diode? Anyone have any knowledge of this?

--
RH
Reply to
Robbie Hatley
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Semiconductor's

So a matter of removing one and testing and plotting out what happens to the knee above 1.5A and effect of reverse >25V

Reply to
N_Cook

Good idea, but I don't have the equipment on hand.

However, I've discovered on further research, that SM marking code "SJ" on Gen Semi (now Vishay) diodes can mean any of several different 600V diodes (the "J" means 600V but doesn't specify current). Fortunately, the current rating is tied to package: "SJ" on DO-214AC (SMA) package = S1J (1.0A, 600V) "SJ" on DO-214AA (SMB) package = S2J (1.5A, 600V) "SJ" on DO-214AB (SMC) package = S3J (3.0A, 600V) "5J" on DO-214AB (SMC) package = S5J (5.0A, 600V)

Fortunately, it seems Vishay doesn't re-use same code on same package for different parts. (Note that since their 5A diode has same package as

3A, they change code from "SJ" to "5J".) So as long as you're careful to observe both the code *and* the exact package (measure carefully, as some packages vary by only a millimeter or so!), finding the exact part should be easy.

(In my case, it's "SJ" on SMA, hence S1J (1A, 600V).)

Caveat: the above is for Vishay only. For diodes made by others, such as Diodes Inc or Nat Semi or Fairchild or International Rectifier or whatever, all bets are off; likely same part has different code for each. And if there's no maker mark, then the only way is to power it up and graph the V/I response curve. (I wish I had suitable equipment here to do that.)

--
RH
Reply to
Robbie Hatley

the

current rating

whatever,

there's

Just a bench ps and standard DVM for knee plot, a "nanoammeter" of some resistors and 200mV DVM range and variac and transformer /rectifier for going well above the ps voltage range in reverse plotting of leakage

Reply to
N_Cook

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