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Replacement JFET... what's difference between transistor?

QSilver

QSilver

Super Member
I'm working on an old organ at the moment and I think I'm gonna need a replacement for a JFET... it's a 2N4360 - the only equivalent I could find was an NTE326. I was hoping someone could point me in the direction of a better one.

Also, I notice tha tthe terminals a DGS and not CBE etc and I wondered what the main difference is between JFETs and normal transistors we use in audio circuits?
 
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ChrisMarantz said:
You can buy the 2N4360 (fairchild) from LittleDiode

Here's a link to some good information about JFETS
Click to expand...

Thanks for the information, really informative, now i know! :) I might order from LittleDiode...

petehall347 said:
20V, Idss>3mA, Up<10V
http://english.electronica-pt.com/components-cross-reference?ref=2N4360
gds is gate drain source as opposed to base collector emitter . as far as i know you cant swap one for the other .
there is a uk seller on that ebay .
Click to expand...

Yes, it seems as though they work in a slightly different way. Is 20V its maximum voltage? I think on my schematic, it has it down as 24.6V on the Gate leg.
 
The 2N5460 might get it done for your application, and has twice the voltage rating but a lower current capacity. It will all depend upon your circuit. It is available at a lot more competitive 94¢ each.
 
Dumb Question: Can JFET's like the 2N5460 get noisy like other transistors. Noise like crackle, hiss ect..?
 
QSilver said:
I'm working on an old organ at the moment and I think I'm gonna need a replacement for a JFET... it's a 2N4360 - the only equivalent I could find was an NTE326. I was hoping someone could point me in the direction of a better one.

Also, I notice tha tthe terminals a DGS and not CBE etc and I wondered what the main difference is between JFETs and normal transistors we use in audio circuits?
Click to expand...
JFETs (DGS) and BJT's (CBE) are completely different animals and cannot be directly substituted one for the other at all. The JFET acts much like a voltage controlled resistance, while the BJT acts like a current controlled current source. They live in completely different surrounding circuitry.
 
TouchSpark said:
Dumb Question: Can JFET's like the 2N5460 get noisy like other transistors. Noise like crackle, hiss ect..?
Click to expand...
I think so, heard in the past folks posting of noisy jfets, after replacing, noise is gone. could be gate/source leakage or other means
 
I don't know that one specifically, but yes they can get noisy. I spent a lot of time chasing noise in my hybrid phono preamp, finally determined it was the JFET at the input, not tubes or resistors like I would have expected. Don't know what the specific fail method was, other than it hissed annoyingly.
 
gadget73 said:
I don't know that one specifically, but yes they can get noisy. I spent a lot of time chasing noise in my hybrid phono preamp, finally determined it was the JFET at the input, not tubes or resistors like I would have expected. Don't know what the specific fail method was, other than it hissed annoyingly.
Click to expand...
I haven't run across any that have failed yet, or became hissy myself.
But I have found BJT's that became noisy. Usually the legs were corroded, turned black. I figured the corrosion crept up into the case to the transistor itself. Some were in sockets, they were the worst. Maybe a reaction between the metals in the socket and legs of the transistors?
 
I've had MOSFETs go noisy in an Adcom GFP-750. Also had JFETs go noisy in another preamp, and an amp front end.
I've also had JFETs drop in IDSS over 40 years of use, and matched dual can JFETs drift well out of match. Same with BJTs, most noticeably with output transistors.
When I first started working with JFETs I also caused failures in a few by not being careful about static electricity. Same with MOSFETs I was using for voltage limiting in tube amps. Static mat and grounding strap solved that problem.
 
I did those two jfets, one per channel, and it quit making nosies. Then I did the mosfets used as plate and cathode loads just because I had already bought them. Made no obvious difference that I noticed but basically everything in the audio path is new now. Every resistor, cap, and silicon part wired to a tube has been done. Its still running a handful of original parts related to the time delay mute circuit and the power supply regulator stuff is also original since its working as expected. I figure that preamp is as good as its ever been. The pots and switches are still fairly crappy though, which is a shame because it sounds nice.


I can't speak about prior abuse, this preamp came to me with the board floating loose in the cabinet and the screw that bonds the board to the case missing. Lots of broken traces, solder, etc. Questionable construction and abuse is a bad mix.
 
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