Stupid J201 question

[stallik]

Well actually, MMBFJ201's. I know that the old through hole devices are out of production and supplies are seriously suspect now but does this apply to the smd equivalent or can I just buy them from anywhere?

[bluebunny]

Yeah, anywhere.  Tesco, Argos, ...   

Seriously, just took a quick gander at Bitsbox: 29p each (23p 10+ off).  Also Tayda for 42c.

[anotherjim]

Thing is to find the real manufacturers' product listings. The "Status" will tell you...
https://www.onsemi.com/products/discrete-power-modules/jfets
...although it can be less obvious who the current manufacturer is. I didn't know it was Onsemi until I started searching.

[stallik]

Thanks, placed order with Bitsbox.
I've been using up my stock of J201's and have run into so many issues I've totally lost trust in anything marked J201. Hopefully, going to SMD will restore my faith...

BTW, Argos are out of stock

[bluebunny]

BTW, Argos are out of stock

The universe has ended.   

[anotherjim]

My bench amp came from Argos (I didn't buy it - it was a gift). It's rubbish really, but it fits on the shelf neatly. I ought to hack it some since I'm sure the little speaker is too much full-range and give a false brightness.

Oh, those smd trannies are so easy to lose. Any good (sticky) tips for handling the little jiggers?

[stallik]

Yeh - don't sneeze!

[deadastronaut]

Buy a load of 2n3904's and just write j201 on them...

But seriously, i havent tried any smd j201, i,ll havd to bite the bullet too as im running out....

[Ice-9]

I use lots of the MMBFJ201's and find the tolerance is closer over a range of these compared to the through hole versions but I do buy a few hundred at a time so they will have come from the same reel and should be very close. I usually buy these from 'RS Components' UK.

[stallik]

My order arrived this morning along with the pcb's from fuzz dog. Sub 24 hours is pretty good at the moment. Would get straight onto it but forgot to order solder paste

[stallik]

As I'm so impatient and could not wait till the solder paste arrived, I thought I'd try using my soldering iron. I learned some stuff

• My finest point tip looks like a torpedo on something this small
• When I hold my breath, my hands stop trembling
• When I let out my breath, the smd component disappears
• I was right to suspect my old stash of J201's

Just for prosterity - my first smd work. I'll wait for the paste before making the other 49..

[anotherjim]

Looks neat to me.
Solder paste is expensive, isn't it?
I've yet to use my stash of smd adapters. I've got the ones Bitsbox sell). I have used some smd directly on perfboard pads. I just put down some ordinary solder on the pads And reflow it onto the smd legs with soldering iron close by. There's just enough flux residue for the solder to flow onto the legs. In the past, I've replaced digital car radio panel controller chips this way. Looking back, I don't know how I managed it. My eyes must have been better then!

I guess you might worry about matching the FET's, but as has been said, they are more consistent now (better tooling and purer silicon?). How do we think the likes of Behringer are making so many cheap clones? The other day I went old school and tried out a silicon fuzz face on the breadboard. Sorting Hfe in a new batch of 2n3904's was a waste of time. They were all too good and nearly identical! I had to look through my stash of ancient PN3643's to find the magic values.

I think it has been said here before that new FX PCB designs might include SOT23 pads between the TO92 holes? And don't forget, only the gate has to match up, source and drain can swap without problems.

[stallik]

I paid £6 for 10ml in a syringe. I'm thought that might be the easiest way for me to use it and, given the amount I'm likely to do, it should last a while.
I think it's possible to solder D&S to TO92 holes and run a fine wire around to the gate but it's a bit of a faff. I intend to make up a stash of boards so I can drop them in wherever needed

[Ice-9]

Kevin, Hand soldering SMD with an iron is pretty easy when you get a little practice. I pretty much hand solder all SMD with my iron which has a 0.8mm pointed tip. For 3 pin jfets etc. i just pre tin one pad put a little flux from a flux pen on all the pads then solder the jfet to the pre tinned pad while holding the component with fine twezzers, then solder the other two pads. As there is flux on the pads the solder flows nicely between the pad and the component lead.

It just takes a little practice. I have used solder paste but don't like that unless I am doing a large board with a solder paste screen template and an oven.

[stallik]

Well the paste arrived this morning so I gave it a go. I have no mask so had to find a way to get a tiny amount onto each pad. I didn't realise that the paste is actually flux filled with tiny balls of solder and it was surprisingly easy for those little balls to end up everywhere.

I have no oven so used the gas powered hot air tool usually reserved for shrink tubing and it worked really well. Those little balls coalesced right back to the pad but I felt somewhat out of control. Because of my aging eyesight, I was using a binocular dissecting scope so perhaps I was seeing too much detail.

I've found a finer tip for my iron but it looks like someone used it as a dart and the tip is flattened. Think I'll repair that and go back to the iron as suggested

Whatever, I've made another 4 of the devils and used them to repair one of my amp buffer/splitters which has been blowing jets like no tomorrow. Power supply issue that I can't track down but that's a different story

[bluebunny]

    2. When I hold my breath, my hands stop trembling
    3. When I let out my breath, the smd component disappears

LOL   


The Universe  1-0  Kevin

[Ice-9]

Kevin, I also use a gas hot air iron with SMD and they really are a great tool that should be in everyone's kit bag. Excellent for reflow or removal of larger IC's.

[deadastronaut]

I had a test smd board with paste and hot air...which was interesting, my first smd experiment..its quite satisfying when you see yhe part settle in place....


But like mick said , when i did my first fv1 i just added normal solder to a pad, placed the chip, warmed it up and got it square..so it holds in place,

Then used my iron for the rest,   i was actually surprised how easy it went...

[moid]

Not sure if it helps anyone but Mouser in the UK still sell J201s in through hole format. They are bloody expensive though. I bought some to make a jawari pedal with and they worked
https://www.mouser.co.uk/ProductDetail/InterFET/J201?qs=OxRSArmBDfyvD8SbvWteMw%3D%3D

I also tried the SMD route, and did make one successful J201 on SMD using the Bitsbox converter board, but it makes my eyes hurt to do it and feels like keyhole surgery!

[Phend]

An old tv commercial I remember.
Which in this case does not include smds. But wait if you order now ...

There is no such thing as a stupid question,  just sometimes stupid answers.