Transistor Questions need advice please

[mr woofer]

Greetings everyone.

I have a couple questions regarding the labeling of Transistors and second inconsistent hfe concerning Saken Transistors bought from Digi key.

# 1 I have noticed that sometimes you will see the traditional white lettering and sometimes Laser etched, specifically on Sanyo and Hitachi and even some Toshiba.
That being said I have some small signal Transistors from the three manufactures I mentioned.
I have even seen them in NAD Rotel Onkyo long story short should I be concerned over this is it true they did use laser etching??

# 2 I recently bought some Sanken Transistor's from Digi key. 2SA1695 2SC4468-and others when checking for the Hfe value I noticed there was no consistency.
Also, three of the Transistors checked as Germanium and some only had an Hfe between 6 & 7 so I'm returning them, just curious if anyone else had any problems.

Thank you for your time and consideration everybody I'm fairly new here and this seems like a very education site!

 

[rayma]

Were the Sankens from Digikey, or actually from the Digikey marketplace (outside vendors)?

 

[mr woofer]

From Digi key usually Marketplace you have to buy in quantity if I'm not mistaken.

Thank you for your question it is a very good point and one I should follow up with Digi key!

Thanks again.

John

 

[rayma]

I've never received, or even heard about, fake part problems with parts Digikey has sold.
But don't hesitate to return them if they are not right. I'm sure Digikey will pay the return shipping.

 

[mr woofer]

Amen Brother!

 

[Elvee]

some only had an Hfe between 6 & 7 so I'm returning them, just curious if anyone else had any problems.

Very strange: even fakes look perfectly OK from the Hfe POV.
The value would be compatible with the reverse beta, E and C swapped

 

[Mooly]

Also, three of the Transistors checked as Germanium and some only had an Hfe between 6 & 7 so I'm returning them, just curious if anyone else had any problems.

I'm assuming you've used some kind of all in one tester do-dah.... I think I would do a quick check using more conventional methods before condemning them.

 

[wg_ski]

It’s pretty hard to swap emitter and collector on a TO-3P. I could see base and emitter backwards. Single digit hFE is what you sometimes measure on old style epitaxial base NPNs at very low current (Tens of micro amps). DMM “hFE” ranges can run that low. The junkers that they put in modern fakes don't usually do that, and if anything, will read too high. But if a faker used something resembling a 1980’s era 2N3055 you could measure single digit hfe on the NPN.

 

[mr woofer]

Thanks very much and understand your point will look into your advice. Thanks

 

[bucks bunny]

As a general rule these hfe-testers operate at currents in the mA range. This is fine for small signal transistors like BCxxx- but not very informative for power transistors operating in the amp range.

 

[jan.didden]

2SA1695 2SC4468-and others when checking for the Hfe value I noticed there was no consistency.

But were they consistent with the data sheet ranges?
Data sheet often specifies ranges that vary a factor of two or more.
What sort of numbers did you read?

Jan

 

[wg_ski]

He mentions 6 to 7, which is not likely for a genuine Sanken epitaxial planar type, even in the uA range. It’s quite possible for prehistoric stone knives and bear skins types at low current (though they may measure 50 at an amp or two). That throws up red flag or at least a yellow card.

 

[mr woofer]

Greetings everyone and many thanks for your questions!

Well, I found out that one of the clips leads on my Peak Instruments was not making proper contact, so the very low Hfe ratings went away.

How ever when comes time to checking Hfe of their 2SC series I'm getting ratings about half of the stated hfe.

Example Sanken 2SC4468-O Per the data sheet should read from 50-100 and I'm getting Anyware between 31-38 Strange
could this be attributed not enough base collector current/Voltage.

Again many thanks to all that responded.

John

 

[Mark Tillotson]

Hfe or hfe? They are different, Hfe is the ratio of DC currents, hfe is derivative of the curve at the specified point, ie the AC current gain. These are quoted at specific voltage and current levels usually, often chosen to give maximum gain 🙂

 

[wg_ski]

Where would you expect it to be at 1uA of base current?
Sankens aren’t likely to get down in the single digits but 30’s seems plausible.

 

[mr woofer]

Greetings Mark sorry for the delay I was preoccupied working on my Onkyo M-5030 Power Amplifier.

Thanks for asking me your Question the one I was Referring to is the Hfe spec.
I agree with you concerning where 1uA would be.

 

[wahab]

As a general rule these hfe-testers operate at currents in the mA range. This is fine for small signal transistors like BCxxx- but not very informative for power transistors operating in the amp range.

Those fake transistors are a nightmare, ultimately i did set for a good precision weighting apparatus, but this require to have
genuine parts at hand for the comparison.

 

[mr woofer]

I would have to agree with you concerning testing transistors. The peak Instrument Transistor is defiantly current limited for Testing TO-126-To220 & TO-3/P