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

[AUDIO FREQ]

I am ware the pin outs are different, but maybe I can bend the legs carefully?

Ive looked around and it seems like china is the only one selling 2sa1084's...and I don't trust it

 

[echo zulu]

The 1989 ECG Semiconductor Master Replacement Guide shows an ECG 129p as a replacement. There are NOS examples of these available on Ebay. The NTE version would probably work, too (although it's probably made in you know where .

 

[AUDIO FREQ]

The 1989 ECG Semiconductor Master Replacement Guide shows an ECG 129p as a replacement. There are NOS examples of these available on Ebay. The NTE version would probably work, too (although it's probably made in you know where).

Holy schnikes! 7 dollars a piece!

 

[Khron]

What role (in the circuit) do those 2SA1084's play?

 

[AUDIO FREQ]

What role (in the circuit) do those 2SA1084's play?

They are the two transistors at the bottom of this transformerless mic pcb. This was my first try ever at a DIY kit, and my soldering job as gotten alot better. Thanks to you guys! I don't want to buy a whole new kit for $150, and would just like to build one using mouser...but I couldn't find any of the said transistors at the bottom. Which are the A1084. So I am looking for alternatives. I also want to try and learn how to bias the J305 jfet on the top portion myself. So it's a project I want to start in order to learn how things are working.

 

[Khron]

BC560's might serve you a bit better though - at least they're spec'd to be "low noise". Although not quite certain just how great of an influence on noise the PNP output transistors are, in a Schoeps circuit.

 

[AUDIO FREQ]

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.

 

[Khron]

Adding fresh extra solder, as counterintuitive as it might sound, will help. That provides more molten solder for the heat to spread through, more uniformly.

No matter how hot your iron is, if you're making contact with the joint only on one narrow corner, that's nowhere near enough for heat to flow through. And the little that does get through, gets heatsunk away by the component legs & copper traces.

 

[AUDIO FREQ]

Adding fresh extra solder, as counterintuitive as it might sound, will help. That provides s more molten solder for the heat to spread through, more uniformly.

No matter how hot your iron is, if you're making contact with the joint only on one narrow corner, that's nowhere near enough for heat to flow through. And the little that does get through, gets heatsunk away by the component legs & copper traces.

Ahhhh ok that makes sense. I guess I was just being paranoid, im gonna practice desoldering on some old broken devices i've collected over the years in my garage, with fresh solder as you said. Thanks Khron!

 

[abbey road d enfer]

https://www.futurlec.com/Transistors/2SA1084pr.shtmlhttps://www.retroamplis.com/epages/...ectPath=/Shops/62070367/Products/TR-2SA1084-E

 

[ccaudle]

Any tips on desoldering transistors?

Desoldering depends on whether you need to keep the old devices, or just replace them. If you just need to replace them cut the component body off, and then you can heat one pin at a time and pull it out. Clean up the solder left in the hole later.

Do you have a solder "sucker" (vacuum removal tool)? Are you using copper braid wick? If you are using copper braid then putting some liquid flux on the braid will help the solder start wicking up the braid, especially if the solder is a little old and has an oxide layer on top. If you are using a solder sucker then cutting the component body off allows the pump to be on one side of the PCB, you can heat from the other side, and then suck out the solder while it is still molten. When you have to melt the solder with the iron, then quickly move the iron out of the way to get the pump on and suck out the solder, the solder will solidify just a bit when you move the iron away so isn't quite as effective.

 

[AUDIO FREQ]

https://www.futurlec.com/Transistors/2SA1084pr.shtmlhttps://www.retroamplis.com/epages/...ectPath=/Shops/62070367/Products/TR-2SA1084-E

Thanks Abbs, but it says its out of stock at that website . This makes me sad.

 

[AUDIO FREQ]

Desoldering depends on whether you need to keep the old devices, or just replace them. If you just need to replace them cut the component body off, and then you can heat one pin at a time and pull it out. Clean up the solder left in the hole later.

Do you have a solder "sucker" (vacuum removal tool)? Are you using copper braid wick? If you are using copper braid then putting some liquid flux on the braid will help the solder start wicking up the braid, especially if the solder is a little old and has an oxide layer on top. If you are using a solder sucker then cutting the component body off allows the pump to be on one side of the PCB, you can heat from the other side, and then suck out the solder while it is still molten. When you have to melt the solder with the iron, then quickly move the iron out of the way to get the pump on and suck out the solder, the solder will solidify just a bit when you move the iron away so isn't quite as effective.

Yeah I have one of those manual cheap solder sucking tools. I use it all the time, but im very inaccurate with it. It takes me multiple tries, because once I hit the button...the force moves my hand away from the solder joint. So I ended up heating the part, way more than need be. I would like to invest in one of those vacuum gun desoldering machines, but they are a bit pricey, and I've heard mixed reviews on the ones from Aliexpress. The hakko one, is not in my price range at the moment.

I do use MG chemicals, desoldering wick braid. But mainly for cleaning, I guess I should give it a shot in desoldering as well.

 

[Newmarket]

https://www.futurlec.com/Transistors/2SA1084pr.shtmlhttps://www.retroamplis.com/epages/...ectPath=/Shops/62070367/Products/TR-2SA1084-E

Took a look on there. They are either limiting orders to 4 off. Or have only 4 in stock. In which case Be Quick

 

[AUDIO FREQ]

I can't, it's located in Europe .

 

[micolas]

A1015 (2SA1015) will work perfectly

 

[micolas]

the two transistors must be paired, have the same hFE

 

[abbey road d enfer]

I've heard mixed reviews on the ones from Aliexpress. The hakko one, is not in my price range at the moment.

I have the ubiquitous ZD-915 for 5 years and never had a single proble with it. OTOH, it's not on 24/7.

 

[AUDIO FREQ]

the two transistors must be paired, have the same hFE

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

 

[AUDIO FREQ]

I have the ubiquitous ZD-915 for 5 years and never had a single proble with it. OTOH, it's not on 24/7.

I have the ubiquitous ZD-915 for 5 years and never had a single proble with it. OTOH, it's not on 24/7.

Just looked it up! Looks affordable, maybe I’ll get one on Christmas