Hi Peter!
> But losing a string that's part of a
> bridge is another matter, and some people may feel all they need to
> do is change that string. Under those conditions, I'm a believer,
> like I gather Manfred is, in changing all the diodes.
Well, I'm not so much a believer in that! I would probably just replace
the string with the failed diode, at least if I know a good reason why
it failed. If I don't know the reason, I might change them all, just to
be sure to eliminate any other diode that could have been degraded by
the same event that burned one.
I mean that it is NOT important to have the diodes of one string closely
matched to those in the other strings. So the only reason to change all
the diodes would be catching any partially damaged one. And they are so
cheap that one can do it just for peace of mind.
> At least with
> silicond diodes, we don't get the problems we had with mercury
> vapour, where they could occasionally arc for no real reason. One
> trick was to put a small coil in each plate lead witha piece of steel
> rod in it it: after the flash over, the steel was magentised, and you
> detect it with a small compass needle. That told you which tube to
> change...
Nice trick! I see you are older than I am! I have seen mercury
rectifiers only in museums! Even the number of selenium rectifiers I
have found in the field is small. I was raised on the 1N4007 and the
1N5408! :-)
Tom:
> So when I call Mouser and order 25 diodes, I know they are all from
the same batch or the same plant on the same day because???????
> Because they are the same color?
> Because I ordered them on the same day?
> Because they never mix bulk inventory in a big bin?
No. You know they are from the same batch because they come tied
together by two strips at the ends of their terminals!
If you get loose diodes, you should check the batch code printed on
them. And if you get loose diodes without a printed batch code, you
should either avoid them or carefully measure their characteristics
before you combine them.
I usually get my diodes tied together!
Manfred.
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http://ludens.cl
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