FirstWatt J2

[ak4396]

A Photocoupler.
Instead of the NPN Transistor, because the low Vgs of the Power-Jfet.

 

[Zen Mod]

The right direction?

value of source/drain resistors

LED positioning

emiter of opto bjt in wrong point

I'll say no more ......

no J2 Babelfish from Mighty ZM

 

[ak4396]

Zen Mod,

now my Brain is running hot ...

and her it is:

The way?

Thank You

 

[Zen Mod]

transistor part - better , but resistor values still not good , same as termination of LED part

........ and - you have few missing parts


google for nelson pass , optical bias , patent

 

[ak4396]

Sorry wrong Picture.

Now the right one:

I have count the Parts in the J2 Picture.
I would say its right (Power-R //).

I will read the Patent and come back

 

[spavleski]

Optocoupler should be galvanically separated

 

[HVfanatic]

I do not see any need for the optocoupler. Why not use a tl431 as Nelson does? maybe supply the tl431 by a CCS to ease its work? I even guess, thats not necessary, I would just put a 220uF cap across it to make it a stiff (whatever so adjusted) voltage offset...

The feedback connection would care for dc stability, and I guess, a 2SJ109 is preferable to single silicon devices...

But hopefully Nelson shares the secret, I have 2sJ109, semisouth ans 2sk170 waiting...

Dirk

 

[yggdrasil]

ak4396 - would you like to share your spice model of that precious device (sjep..) or point me in a useful direction.

 

[Tea-Bag]

But hopefully Nelson shares the secret, I have 2sJ109, semisouth ans 2sk170 waiting...

Dirk

Well, that takes the fun out of cloning. Nelson gave us enough details to start with, and 6moons photo's help. We now have some parts lying around, fire up the science lab and let's roll up our sleeves and go for it.

 

[ak4396]

my LT-model
Not very good but at 1,5-2,5A not so bad.

 

[ak4396]

My last idea.

In my mind it is the way to hold the Voltage constant like we see it in the simple schematic form Mr. Pass.

Or not?

 

[bobodioulasso]

The opto led has to monitor the voltage across R14+R8.

 

[ak4396]

Than you can do so.

 

[Zen Mod]

Than you can do so.

 

[Nelson Pass]

I would stick a nice big cap across Q2

 

[Zen Mod]

baad Papa , baaad!

 

[eyoung]

What about the tl431 instead of opto whatever???

I just dont have a good tl431 spice model that works,

Just a thought, El

 

[Nelson Pass]

Works fine, but you have to adjust it by hand after the
circuit has warmed up.

 

[yggdrasil]

TL431 spice model.

 

[generg]

hi everybody,

maybe I just heard half of the heaven J2 promises....

I got tea-bags semisouth and put them together with the semisouth I got from magura in a BA-1. I left the IRF240 on the negative side doing the job as a current source and ,like Nelson would say, not to spoil the performance of the output stage by the gainstage I changed the IRF610 by a semisouth R100.

Wonderful performance, more details, voices totally different and subtle.

So I can wait for J2 in any version much better!
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