Cant find any 2sa1084...can i replace them with 2n5401?

[AUDIO FREQ]

A1015 (2SA1015) will work perfectly

I have some of those! I’ll give them a shot!

 

[Ricardus]

How do I measure the hfe? I have an oscilloscope and a breadboard.

These work fine:

https://www.ebay.com/itm/394799571112?hash=item5bebe360a8:g:4BEAAOSweahk0bYM
And I have one of these:

https://www.peakelec.co.uk/acatalog/dca75-dca-pro-semiconductor-analyser.html

 

[abbey road d enfer]

How do I measure the hfe? I have an oscilloscope and a breadboard.

You can set-up a rig on a breadboard; it's not terribly difficult but also not very practical.
https://www.biophysicslab.com/2021/04/27/testing_transistor_hfe/And if you make a mistake, you run the risk of destroying the tranistor you test.

Now, many cheap multimeters have a transistor test capability.
https://www.amazon.fr/OocciShopp-Mu...ywords=multimeter&qid=1692221734&sr=8-50&th=1
Or, you can use that
https://www.amazon.com/HiLetgo-Tran...ords=transistor+tester&qid=1692221641&sr=8-20Best solution IMO.

 

[AUDIO FREQ]

20 bucks! Looks like this is the ticket! Thanks Abbs!

 

[micolas]

hfe is simply measured with a digital multimeter

 

[AUDIO FREQ]

Sadly mine doesn’t have this feature

 

[micolas]

the multimeter must have hfe measurement function
yours truly cannot measure transistors

 

[micolas]

A good pairing of these final transistors helps to minimize the distortion that can occur at the output

 

[AUDIO FREQ]

A good pairing of these final transistors helps to minimize the distortion that can occur at the output

I will buy the device that abbs linked from Amazon.

 

[micolas]

The micparts kit contains matching parts and pre-biased jFET for maximum headroom. Each jFET can be very different, so the bias must be adjusted individually, either J305 or 2N3819. I like the latter better.

 

[micolas]

A possibility to adjust the bias for the jFET.
Adjustable resistor can be 470k...1M and R12 is 1Gohm
Of course the original schematic of the micparts kit must be modified

 

[Ricardus]

20 bucks! Looks like this is the ticket! Thanks Abbs!

My link was cheaper!!!!

 

[AUDIO FREQ]

My link was cheaper!!!!

Oops! I only saw the second link!

 

[AUDIO FREQ]

The micparts kit contains matching parts and pre-biased jFET for maximum headroom. Each jFET can be very different, so the bias must be adjusted individually, either J305 or 2N3819. I like the latter better.

I have a 2n3819! I will try this! Thank you!

 

[AUDIO FREQ]

A possibility to adjust the bias for the jFET.
Adjustable resistor can be 470k...1M and R12 is 1Gohm
Of course the original schematic of the micparts kit must be modified

So do I just use a multimeter on the third leg and just for 0 vdc?

 

[Philbo King]

My desoldering skills need some serious work. As you can see the throughhole eyelet I managed to tear off, I had to insert a pair of copper eyelet in on C14. I managed to get everything off, but I don't think the A1084's survived my noob attempt. I need to learn to be patient before pulling at components. Any tips on desoldering transistors? Im scared to hold the iron too long on the pins, so I eagerly pull at them while heating up the joints.

Mouser seems to not carry those BC560. I have a few other transistors some old broken devices i collected throughout the years, I can try and desolder. So far I see,

J108
C2240
KN3904
C1815
A1015
KIA79
KIA78L
431A
MPS A92
2N3819
LSK389
LKSK489
K170A
U441/ST
A561
C1681
A970

Some of these are really old...so Im not sure how time affects transistors...or heat from desoldering attempts.

Put an alligator clip (known in some circles as a roach clip) on each lead between the body of the part and where you are soldering. It diverts the heat away from the part.

If the iron is in contact with the solder joint for 7 seconds, pull away, let it cool, and try again. Never yank on a lead unless the solder is fully melted.

 

[AUDIO FREQ]

Put an alligator clip (known in some circles as a roach clip) on each lead between the body of the part and where you are soldering. It diverts the heat away from the part.

If the iron is in contact with the solder joint for 7 seconds, pull away, let it cool, and try again. Never yank on a lead unless the solder is fully melted.

Ooooooo I have some alligator clips! Non copper though, does that matter?

 

[Philbo King]

Ooooooo I have some alligator clips! Non copper though, does that matter?

Nope. As long as they are metal.

 

[Whoops]

How do I measure the hfe?

Buy one of these units for very cheap, and you can measure HFE in transistors and test a lot of different components

 

[Whoops]

Cant find any 2sa1084...can i replace them with 2n5401?​

I did a post here lately that has a lot of links for sites dedicated to transistors cross references and substitutes, check it out here:

https://groupdiy.com/threads/useful-transistor-equivalence-cross-reference-websites-list.84850/
I searched in those websites, and this is the list they give for 2SA1084 replacements:

2SA970
2SA1049
2SA1136
2SA1335
BCW85
2N5333
KT932A
2SA0879
2SA100
2SA1001
2SA1002
2SA1003
2SA1004
2SA1005
2SA1006