transistor oc139 equivalent ?

[andare]

@AurEL. you should pick up this cheap component tester called TC1, available pretty much everywhere.



It reads resistors, capacitors, diodes and transistors and it tells you if they are PNP or NPN, it shows you the pinout and it measures hFE and, for Germanium transistors, Iceo (the leakage).

Most Germaniums are PNP, most Silicons are NPN so choose the appropriate type for your build as per the docs.

 

[Feral Feline]

I had to re-read that Transistor Substitution Chart... I thought it read:

"Be careful of fakes on eBay, Mouser.com, Digi-key.com, SmallBear and several other electronic parts vendors..."

Fake Ge trans on Mouser, Digi-key and Small Bear?



A simple paragraph break or a reconstructed sentence with the legit vendors would prevent mistaking that period after eBay for a comma...


"...Be careful of fakes on eBay.
Mouser.com, Digi-key.com, SmallBear and several other electronic parts vendors..."


Great chart though, looks like an update (much needed) of this ol' chestnut:

 

[Cybercow]

Great chart though, looks like an update (much needed) of this ol' chestnut:

View attachment 33057

Like this one . . . . ?

 

[Feral Feline]

Like this one . . . . ?

View attachment 33058

Yeah, that's the one, the same one you posted earlier in the thread.

Reading it again, it still looks like "...beware of fakes from eBay, Mouser.com, Digi-Key.com, SmallBear ...".

 

[Cybercow]

Yeah, that's the one, the same one you posted earlier in the thread.

Reading it again, it still looks like "...beware of fakes from eBay, Mouser.com, Digi-Key.com, SmallBear ...".

Good point and catch. Thanks! I corrected them to reduce the confusion.

 

[Feral Feline]

Thanks for those @Cybercow! Didn't realise that was of your own making!

I've been using the old one for years, so if that's yours as well I can't thank you enough for both the old and the new!

 

[Cybercow]

Thanks for those @Cybercow! Didn't realise that was of your own making!

I've been using the old one for years, so if that's yours as well I can't thank you enough for both the old and the new!

Oh, no, no, no . . . . I mean thanks, but I am not the creator of that chart. Like you, I found the old one years ago. A few years a go I updated it and started to re-propagate it across the groups and forums. The proximity of the words "fakes from eBay. Mouser.com, Digi-Key.com . . . " was an oversight on my part.

 

[Feral Feline]

Good on ya for updating it!

Many thanks!

 

[Andyisdumb]

Another point of interest regarding Ge BJTs is that most of them are VERY temperature sensitive. The OCxx and Cvxxxx series are more stable than others, but still subject to changes in ambient temperature. Silicon transistors are far more stable and do NOT exhibit a measurable "leakage" - which also fluctuates with temperature changes.

Just use a socket for the BJT and you can try a few different NPN trannies out. You might want to socket R3 as well. Often, when swapping out different BJTs, the biasing resistor value may need adjusting. And as fig points out, the 2N22222 should work just fine. Still I'd socket the BJT and R3 to try different things. When you find a good working combo of BJT and R3 value, you can solder them in place.

Cheers!

Unrelated question, but why on the PCB are there four holes for the transistor? What is my simple newbie brain missing?

 

[DAJE]

Unrelated question, but why on the PCB are there four holes for the transistor? What is my simple newbie brain missing?

Different transistors have different pinouts. Meaning, you have to make sure which leg is which before you plug it in. Plugging a transistor in the wrong way will not work and could possibly damage the transistor.

EDIT: There are different holes to accommodate different configurations. Just use the one that lines up with what you have and ignore the 4th hole.