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My Transistors, original or copy?
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Old 25th September 2018, 11:55 PM   #1011
MadInventor is offline MadInventor  United States
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Quote:
Originally Posted by cv1040 View Post
The Peak tester in the background gave some fairly close traces for ID vs. VDS, but based on the awful font, the IDSS way out of range, I'm pretty sure these are fakes, anyone disagree?
What is the Forward transfer admittance Yfs read? If it's below say 10mS or at about 5mS, then probably, but they could have been mislabeled, could be Vs.

Mad
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Last edited by MadInventor; 25th September 2018 at 11:57 PM.
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Old 26th September 2018, 01:22 AM   #1012
anatech is offline anatech  Canada
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My Transistors, original or copy?
Hi cv1040,
Time to get out your equipment and take real readings on these things. Not impressed with the PEAK instruments. They look fine.

-Chris
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Old 26th September 2018, 09:32 AM   #1013
petoluk is offline petoluk  Czech Republic
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Quote:
Originally Posted by cv1040 View Post
I bought some SK170BL's from a UK based ebay dealer.

The ammo packaging gave me confidence that they were 'ok' and a cost any faker wouldn't want to incur. However, when they arrived all was not well, the font looks awful.
It's been confirmed by multiple sources, e.g. the trusted eBay seller alweit, that Toshiba's very old production runs used a different, printed (not laser etched) font - one that, AFAIK, matches what you've got there; see also the attachments.


But your IDSS is indeed way too high...
Attached Images
File Type: jpg J74_Original.jpg (111.3 KB, 95 views)
File Type: jpg K170_Original.jpg (180.0 KB, 94 views)
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Old 26th September 2018, 12:15 PM   #1014
cv1040 is online now cv1040  United Kingdom
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Quote:
What is the Forward transfer admittance Yfs read? If it's below say 10mS or at about 5mS, then probably, but they could have been mislabeled, could be Vs.

Mad
@MadInventor I measured Yfs at about 30 mS - a bit higher than the data sheet value of 22 mS (typical). I didn't measure them all, but with the Idss being consistent I figure the Yfs will be about the same too for the batch (of 12).


Quote:
Hi cv1040,
Time to get out your equipment and take real readings on these things. Not impressed with the PEAK instruments. They look fine.
@anatech I did the Idss measurements on a simple rig with a fresh 9 V battery (actually 9.5 V), used 3 separate milliamp meters, results were all very similar. IDSS in the range consistent with V grade devices.

Just curious - what don't you like about the Peak instruments? I just got a DCA75, I was proud of it up to yesterday, not so sure now.


@petoluk - your photos are very helpful. I acknowledge that the devices I have are very probably Toshiba originals now, albeit with IDSS out of range.

I will return my 2SK170's to the original dealer and acquire some more elsewhere. I see NicMac has plenty available..
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Old 27th September 2018, 06:06 AM   #1015
davidsrsb is offline davidsrsb  Malaysia
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These look genuine, there is a large production spread in Yfs and fakes have very low gain
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Old 27th September 2018, 10:23 AM   #1016
WalterW is offline WalterW  Netherlands
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My Transistors, original or copy?
Look at the rough surface, looks like they sanded them and reprinted the typenumber.
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Last edited by WalterW; 27th September 2018 at 10:38 AM.
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Old 27th September 2018, 10:37 AM   #1017
WalterW is offline WalterW  Netherlands
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My Transistors, original or copy?
30mS is good, they are usually much higher than the 22mS, but 18-20mA Idss for a BL, that's way to high.

Are you sure you measured the Idss well? Not only with the tester?
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Old 27th September 2018, 11:44 AM   #1018
cv1040 is online now cv1040  United Kingdom
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Quote:
30mS is good, they are usually much higher than the 22mS, but 18-20mA Idss for a BL, that's way to high.

Are you sure you measured the Idss well? Not only with the tester?
@WalterW. My Idss rig is dead simple, I guess they all are, I measured the Idss current direct from the DMM. Since I wanted extra reassurance, I got a 2nd DMM and used it, similar results, then an old analog moving coil DC ammeter, again similar results. Way too high IDSS.

I packed the units up and was about to send them back. You wrote your message and I had a bad dose of self doubt, so I found a 1 Ω, 1 % resistor and decided to make voltage measurements instead - just to be sure.

Ran the tests again, [insert picture of CV1040 eating humble pie] they test OK. I won't be making low current reading with any of my DMM's again.

Somewhat embarrassed, but they were genuine all along. I looked again really closely with my magnifying glass in direct sunlight, they have not been sanded. For sure the font is not as elegant as some other SK's but as others have shown it is still ok.

Thank you to contributors on this thread, I'd have sent them back without your help.
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