If you do a Google search, you'll find numbers of threads already here, by people in your position, trying to replace 2SK150A and other dual JFETs that once were popular devices. Browse them if you haven't already and get some understanding of the problem.
Through-hole JFET parts everywhere, are virtually obsolete now - at least, no longer manufactured by the major players, so specialty dual or dual matched components are an even rarer commodity. SMD duals like LSK389 are available, but SMD is another deal. You need to consider the soldering techniques and tiny adapter boards necessary to fit these, assuming they are suitable or adaptable as substitutes.
Otherwise the original parts will be very expensive if not unobtanium but you will probably find copies and fakes that are available on the internet, though most likely, out of spec. or simply unsuitable or noisy versions.
Through-hole JFET parts everywhere, are virtually obsolete now - at least, no longer manufactured by the major players, so specialty dual or dual matched components are an even rarer commodity. SMD duals like LSK389 are available, but SMD is another deal. You need to consider the soldering techniques and tiny adapter boards necessary to fit these, assuming they are suitable or adaptable as substitutes.
Otherwise the original parts will be very expensive if not unobtanium but you will probably find copies and fakes that are available on the internet, though most likely, out of spec. or simply unsuitable or noisy versions.
2SK150 is essentially the dual version of 2SK117 (TO92).
http://www.geocities.jp/mason_ishiatama/thesedays/thesedays2006_07_30/2sk150.pdf
2SK117 is discontinued but replaced by 2K209 which is SMD (SOT23).
There is also a dual version of 2SK209, namely 2SK2145 (SOT23-5).
The unfortunate thing is that the two Source pin are wired together internally.
So it depends on the actual circuit as to whether it can be a direct replacement.
(If I am not wrong you can use 2K2145GR to replace X139, X140 but not X301, X302).
2SK2145GR is in stock at Mouser for ca. USD0.8.
2SK2145-GR(TE85L,F Toshiba | Mouser
You will certainly need some kind of adapter board.
If you can find 2SK117GR, you can buy a bunch and match them to make up a dual pair.
The advantage is that they are leaded, so you can wire direct without an adapter board.
At most you need to couple them thermally.
But with GR grade, you have little dissipation (and hence thermal drift) and therefore probably not necessary.
Unlike 2SK2145, you can use them at all locations.
Google says you can get them from a dealer at Amazon.
Have not used that source before, so no idea how reliable the vendor is.
But you probably have some protection dealing through Amazon ??
Patrick
http://www.geocities.jp/mason_ishiatama/thesedays/thesedays2006_07_30/2sk150.pdf
2SK117 is discontinued but replaced by 2K209 which is SMD (SOT23).
There is also a dual version of 2SK209, namely 2SK2145 (SOT23-5).
The unfortunate thing is that the two Source pin are wired together internally.
So it depends on the actual circuit as to whether it can be a direct replacement.
(If I am not wrong you can use 2K2145GR to replace X139, X140 but not X301, X302).
2SK2145GR is in stock at Mouser for ca. USD0.8.
2SK2145-GR(TE85L,F Toshiba | Mouser
You will certainly need some kind of adapter board.
If you can find 2SK117GR, you can buy a bunch and match them to make up a dual pair.
The advantage is that they are leaded, so you can wire direct without an adapter board.
At most you need to couple them thermally.
But with GR grade, you have little dissipation (and hence thermal drift) and therefore probably not necessary.
Unlike 2SK2145, you can use them at all locations.
Google says you can get them from a dealer at Amazon.
Have not used that source before, so no idea how reliable the vendor is.
But you probably have some protection dealing through Amazon ??
Patrick
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Just ensure they are physically touching each other. Wrap them with nylon tie if possible. When the parts are so close anyway on the PCB its less of an issue because they are pretty much equal anyway. That preset pot under the FETs on the diagram allows you to trim the DC offset to zero at the speaker output. Any thermal drift as one of the pair changes temperature shows as slight shift in the offset. If both change together then the offset cancels.
Thank you Mooly!
Now, it a matter of tracking down the legitimate parts, not cheap knockoffs!
Glenn
Thanks Patrick.
There's a couple other parts I'm also trying to find for the same PC board.
2SC2546(E)-Hitachi
2SK105(F)-NEC.
These appear to be corroded a bit from the cap glue. Maybe this could be the cause of the static-noise issue? Right between the heat sink and cap. I've cleaned that all out now. Here's a pic.
Glenn
I doubt its the issue because that is part of the regulated power supply and so common to both channels. It needs attention though.
The 2SC device is a general purpose NPN. You could replace that with a 2N5551 or similar. Watch the pinouts... different.
The 2SK FET is used as a current source and so in one sense non critical but replacements (equivalents) could well give a different value of current. Measure the voltage across R611 and R612 and calculate the actual current. Then you have a reference and could always adjust those resistors up or down to get a similar (doesn't have to be exact) current. Another good and cheap option is to replace the FET+resistor with a constant current diode. I can't just quote any device numbers though.
The 2SC device is a general purpose NPN. You could replace that with a 2N5551 or similar. Watch the pinouts... different.
The 2SK FET is used as a current source and so in one sense non critical but replacements (equivalents) could well give a different value of current. Measure the voltage across R611 and R612 and calculate the actual current. Then you have a reference and could always adjust those resistors up or down to get a similar (doesn't have to be exact) current. Another good and cheap option is to replace the FET+resistor with a constant current diode. I can't just quote any device numbers though.
Attachments
Is this a suitable replacement for the 2Sk150A(GR)?
I found these 2SK117GR which was suggested as a suitable replacement, needing a pair for each channel.
http://www.amazon.com/2SK117-2SK117GR-N-Channel-14mA-transistor/dp/B00KHMOT2Q
or these which look more like what I need.
http://www.ebay.com/itm/4-X-MATCHED-GENUINE-TOSHIBA-2SK117-2SK117GR-N-CHANNEL-FET-/261135535891
Thanks, Glenn
I found these 2SK117GR which was suggested as a suitable replacement, needing a pair for each channel.
http://www.amazon.com/2SK117-2SK117GR-N-Channel-14mA-transistor/dp/B00KHMOT2Q
or these which look more like what I need.
http://www.ebay.com/itm/4-X-MATCHED-GENUINE-TOSHIBA-2SK117-2SK117GR-N-CHANNEL-FET-/261135535891
Thanks, Glenn
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First one shows nothing, second picture are Chinese production nearly good copies.
This one is good 2SK117 Japan Transistor | eBay arrange the source resistor value accordingly.
This one is good 2SK117 Japan Transistor | eBay arrange the source resistor value accordingly.
> second picture are Chinese production nearly good copies ....
I am not so sure.
We have bought over the years genuine Toshiba TO92 JFETs which come on tapes with such bent leads at 2.54mm pitch.
They look very much like those in the 2nd picture, including the silk screen lettering.
In fact the 2SK170BLs from Zhou Fang also look similar.
Not that I declare them genuine from the pictures alone.
The only way to be sure is curve trace.
Patrick
I am not so sure.
We have bought over the years genuine Toshiba TO92 JFETs which come on tapes with such bent leads at 2.54mm pitch.
They look very much like those in the 2nd picture, including the silk screen lettering.
In fact the 2SK170BLs from Zhou Fang also look similar.
Not that I declare them genuine from the pictures alone.
The only way to be sure is curve trace.
Patrick
The German store BL type at 1 Euro each is genuine. You will only need to perform a breadboard test to match the now current derived by Vdrop across the 470R with maybe higher new source pin resistors.
Genuine 2SK117GR you will find in USA at Ampslab online store but in no less quantity than 20pcs for $20 plus postage.
Genuine 2SK117GR you will find in USA at Ampslab online store but in no less quantity than 20pcs for $20 plus postage.
Yup, just saw that.
I'll order some from the other supplier for now. Figure at least I'll have something to get started while I keep searching.
On the 2SK150A(GR) what does the GR signify? I found one listed with out the GR. Will this work as a suitable replacement?
Thanks, Glenn
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