"N_Cook" wrote:

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

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