Source for KSC3503 ?

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Joshvi in the swap meet section is selling them - not seen anything negative and the one pair (of 10 pair purch.) I have used worked fine.
Cheap Chinese transistor tester had them all pretty close specs.

Search “VAS transistors” in the swap meet section.
 
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Buy 30 of the D-suffix parts from DigiKey or Mouser at USD 0.34 per unit. Test them yourself to learn what fraction of the population meets the E-suffix or F-suffix specification. If that fraction is sufficiently large, simply buy (1.05 / fraction) x Quantity_Needed and test. Your effort is rewarded; you get unobtanium transistors in exchange for labor hours invested.
 
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If you are absolutely certain that there is zero point zero probability that a KSC3503"D" purchased today from Mouser.fr, will meet either the "E" or the "F" specifications,

then don't waste your 9,84 € to purchase 30 experimental test units. You know the results beforehand, with perfect certainty.

On the other hand, if you are unsure, then maybe 9,84 € is a good investment, a shrewd wager, to find out the answer in real life rather than in theory.

In my view it is a small cost but of course others may have a different opinion.
 
They don’t vary very much within a batch, but can vary a lot from batch to batch. You could get unlucky and get a D batch that’s right in the middle of the distribution, then you’re screwed. If you got one centered high, you might get some that would pas the E spec. Roll the bones. And what you buy this week may or may not resemble the next batch they get in - and they often have long lead times when they do deplete their stock so it may be a while before another batch is available.
 
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Just an FYI --

Fairchild made and sold the 2SC3503F (begins with "2", ends with Foxtrot); Sanyo wasn't the only manufacturer. A few years ago I bought some of them from Rochester Electronics, see photo 1 below. I apologize that I didn't notice that two of them were faced the wrong way! All of them are indeed 2SC3503F devices, all from the same date code.

Fairchild also made and sold the KSC3503E (begins with "K", ends with Echo). Quite a while ago I bought some of them from Mouser, see photo 2 below. This time I managed to get all of the logos facing the camera.

You might consider this to be bad news, if you only want Sanyo parts. It means you might stumble upon some genuine 2SC3503F devices, only to discover they were made by Fairchild not Sanyo.

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Sorry to destroy hopes but unless they have NO suffix (like generic BC546 which could be A, B or C but sorting costs money and for driving relays it does not matter) the chance of finding F types in a bag labelled D is pretty slim.

I orderd 25 each of both the 1381 and 3503 in D and E, 2x CDIL and 2x OnSemi, and tested for beta:

The bag of 1381D measured 83, 82, 83, 81, 82, 82, 83, 82, 83, ...
The bag of 3503E measured 155, 153, 156, 155, 154, 155, 153, 157, 155, ...
The bag of 1381E measured 110, 111, 113, 110, 112, when I stopped.

By the way I also tested early voltage of 15 (mostly VAS) transistor types under 5 different currents while looking for beta, where can I put the results? Or is it worth starting a thread? I mean this thread is about where to buy, not what type to use.
 
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