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Old 30th Jan 2019, 10:26 am   #1
Malcolm T
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Default Japanese Transistors and identification?

Can anyone tell me please where i can find info on the equavalents for Japanese trannies , FET,s MOSFET,S namely 2SK19, 2SA733, 2SC945 and everything else Japanese into more familiar designations like BC BF BLY or MPF.
The Japanese stuff is a bit of a mystery.
I have quite a few components for identification too so how do i go about finding out what these unmarked packages are , they could be FET,s or Trannies , mostly from the 70s and 80s.

Thanks
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Old 30th Jan 2019, 11:09 am   #2
paulsherwin
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Default Re: Japanese Transistors and identification?

Just google the names. 2SK is the Japanese prefix for an FET.
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Old 30th Jan 2019, 11:17 am   #3
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Default Re: Japanese Transistors and identification?

The go-to for this sort of thing used to be 'Towers International Transistor Selector'. I've just found a browseable copy online here.

https://archive.org/details/TowersIn...sistorSelector

Be aware that as this is quite an old publication, some of the transistors suggested as substitutes may be as hard to find as the Japanese ones you want to replace.
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Old 30th Jan 2019, 11:40 am   #4
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Default Re: Japanese Transistors and identification?

The 2SA733/2SC955 are a complementary PNP/NPN general purpose pair and can be replaced with lots of general purpose types from different naming conventions, e.g. BC558/BC548 or 2N3906/2N3904. Check the leadout arrangements and modify as necessary.

Why do you want to replace these transistors though? They rarely fail.
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Old 30th Jan 2019, 12:41 pm   #5
Malcolm T
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Default Re: Japanese Transistors and identification?

Thanks for the help. Oh yes Towers I remember that book. I'm looking to sort out what I have and identify them and use them in projects or if I don't have them obtain the more recognisable equivalents. I'm just not au fait with Japanese coding. If it's BC, BF or 2N it means something to me.
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Old 30th Jan 2019, 12:51 pm   #6
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Default Re: Japanese Transistors and identification?

I have quite an old edition of Towers which I find quite useful, also several by now old Mullard Data Books (remember those?), and two comprehensive books published by 'Dov' (the 'o' should have a umalaut-two dots above it, b.t.w.), which I bought from Willow Vale back in June 2001. One covers Transistors from A to Z, the other , those prefixed 0 -u (mu). These are all very useful, though now quite old. Data sheets for probably thousands of devices are these days available on the internet of course, but whether any more up-to-date books are available I know not.
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Old 30th Jan 2019, 1:21 pm   #7
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Default Re: Japanese Transistors and identification?

As a very general rule:

2SA = PNP small signal
2SB = PNP power
2SC = NPN small signal
2SD = NPN power
2SK = FET

It's not completely consistent though, and the prefix doesn't indicate Ge or Si. You just have to google the datasheet.
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Old 30th Jan 2019, 1:54 pm   #8
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Default Re: Japanese Transistors and identification?

The other thing to be aware of is that some manufacturers dropped the 2 and sometimes the S as well, when marking their devices. So, a transistor with the legend C945 will be a 2SC945.

Alan
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Old 30th Jan 2019, 3:18 pm   #9
Malcolm T
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Default Re: Japanese Transistors and identification?

Yes and I still have the small Mullard books from 1974 and 75 purple and green! Great little books.

I just don't get along with that japanese legend ident. Thanks for the info again.

So in place of the 2SK19 I could go for a 2N3819?
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Old 30th Jan 2019, 3:53 pm   #10
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Default Re: Japanese Transistors and identification?

They are similar devices, but substituting FETs is always tricky because they tend to have very specific bias requirements. Bipolar transistors are much easier to sub, particularly general purpose types.
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Old 30th Jan 2019, 6:41 pm   #11
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Default Re: Japanese Transistors and identification?

Is there any way of telling from the prefix or number whether a particular transistor is intended for RF or AF applications ?
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Old 30th Jan 2019, 7:17 pm   #12
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Default Re: Japanese Transistors and identification?

Quote:
Originally Posted by paulsherwin View Post
As a very general rule:

2SA = PNP small signal
2SB = PNP power
2SC = NPN small signal
2SD = NPN power
2SK = FET

It's not completely consistent though, and the prefix doesn't indicate Ge or Si. You just have to google the datasheet.
I agree with this summary generally, and would add also 3SK (often dual gate FETs)

There are quite a few 2SCs which are NPN medium to high power (typically TO126 or TO220) devices rather than T092 small-signal.
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Old 30th Jan 2019, 7:26 pm   #13
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Default Re: Japanese Transistors and identification?

And lots of 2SBs are actually pretty weedy, especially from the 60s Ge era.

The prefix doesn't indicate anything about the hfe, as with the American 2N convention. You just have to look them up.
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Old 30th Jan 2019, 7:41 pm   #14
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Default Re: Japanese Transistors and identification?

Quote:
Originally Posted by Malcolm T View Post

So in place of the 2SK19 I could go for a 2N3819?
If you're drawing that conclusion from the fact they both end in '19' I would say no, there was no such intentional co-relation between Japanese, American and European numbering series as far as I know. Each went their own way, mostly.

The '2S' in 2SK19 makes it a FET, as Paul said - you won't find it in the online Towers I linked to earlier because there was a whole separate volume - 'Towers International FET Selector' dedicated just to FETs. I wasn't able to find an online copy in the short time I spent looking.
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Old 30th Jan 2019, 8:01 pm   #15
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Default Re: Japanese Transistors and identification?

According to my copy of Towers' it's the K that is used to designate an n-channel FET. J (ie, 2SJ) in the same position is for p-channel FETs under the JIS system.

Alan
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Old 30th Jan 2019, 8:01 pm   #16
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Default Re: Japanese Transistors and identification?

Quote:
Originally Posted by ajgriff View Post
The other thing to be aware of is that some manufacturers dropped the 2 and sometimes the S as well, when marking their devices. So, a transistor with the legend C945 will be a 2SC945.

Alan
On the other hand, the Japanese were not the only ones to drop letters. A C33825 is actually a BC338-25 from Philips. Likewise a C557C would be a BC557C. You can often also recognise them as not-Japanese by the shape of the housing.

Another thing to keep in mind, is that on a Japanese transistor, the second line of text is usually the batch code, but it can also start with the suffix. For example a transistor marked C1815 GR1A is a 2SC1815-GR (with batch code 1A). I think GR is a hFE designator in this case.

Last edited by Maarten; 30th Jan 2019 at 8:07 pm.
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Old 30th Jan 2019, 8:05 pm   #17
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Default Re: Japanese Transistors and identification?

All very true. I was talking in terms JIS devices made in Japan.

Alan
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Old 30th Jan 2019, 8:06 pm   #18
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Default Re: Japanese Transistors and identification?

Quote:
Originally Posted by Jolly 7 View Post
Is there any way of telling from the prefix or number whether a particular transistor is intended for RF or AF applications ?
I think the Japanese system started out distinguishing between RF and AF, not between small signal and power but it seems that it got mixed up a bit, later.
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Old 30th Jan 2019, 8:14 pm   #19
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Default Re: Japanese Transistors and identification?

Towers' again:

2SA - pnp, high frequency
2SB - pnp, low frequency
2SC - npn, high frequency
2SD - npn, low frequency
2SH - unijunction
2SJ - fet, p-channel
2SK - fet, n-channel

Alan
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Old 31st Jan 2019, 12:30 am   #20
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Default Re: Japanese Transistors and identification?

The "S" number actually designates the number of PN Junctions in a given device, hence 1S XXX for Diodes ie. one PN junction, 2S for Transistors ie. two PN junctions, and 3S for the likes of Dual gate Mosfets.
The US system is similar in this regard, ie. 1N XXX for Diodes, 2NXXX for Transistors and so on.
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