While they last...

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#882
danny_66 said:
Not.
You ask the manufacturer of those Al2O3 insulators if they can make them to your custom specs.
Click to expand...

If you are going to ask for custom spec insulators then inquire AlN (Aluminium nitride). AlN has 4-5 times better thermal conductivity then Al2O3 oxide.

For TO220 TO247 transistors AlN insulators are available on the market but have never seen TO-3 or Tokin versions of them.
 
#886
The alumina sheet could be cut with a tile saw. This will be limited to straight cuts, but it should be possible to make an esthetically pleasing prismatic shape. You can drill holes the brass tubing and an abrasive slurry. Use some putty to make a dam around the hole location. Turn the tube fairly slowly, a couple of hundred rpm. Having a drill press really helps.
 
#887
Western Electric GA-10654 Magnetic Amplifier

Soundhappy said:
Look at this Ebook about Magnetic Amplifiers https://www.rsp-italy.it/Electronics/Books/_contents/Magnetic amplifiers - Mali - 1960.pdf
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@Soundhappy - that book was a surprisingly clear and well written that a newbie like me can understand some parts.

Amazing that magnetic amplifiers have been around since 1885, and were used in WW2 long range missiles, control systems for making germanium and silicon transistors, and even in nuclear reactors. So they were made to replace tubes in harsh environments, but can also be used for amplification.

I'm am in no better position now in knowing how to use the 15 pin components, but I at least have more background knowledge as to what they can be used for. If I ever find a pinout or data sheet, I'll update you

So they are pretty rare components, I will keep an eye out for more if you think they could be used to some success with audio?

Thanks for passing that information on to me, most grateful.
 
#889
contemplating transformers for couple of projects

Nelson Pass said:
...Now it looks to me like the inventory of Tokin VFETs (2SK180, 2SK182 and
THF51S) will follow the same path. The stock is limited and they aren't
making any more...

I am contemplating a couple of projects using them, and I advise anyone
who wants to play to acquire them while you still can.
:cheers:
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@Nelson Pass - Took your advise, purchased some 2SK182 and THF51S (put them in a safe box). 🙂

In regards to the couple of projects you are contemplating, what would be the upper range of the output power that you had in mind?

I am trying to plan ahead (to build a PSU I can reuse across FW projects) so I am trying to specify power transformers VA, and I read 'somewhere' that "Nelson recommends a minimum of 7.5 times the output power of each channel. So an Aleph-J produces ~25wpc. 25 * 7.5 * 2 = 375VA"

I don't know if at this time, you might not be able to advise, but I would be very grateful if you could :angel:
 
#890
rootscript said:
@Soundhappy
So they are pretty rare components, I will keep an eye out for more if you think they could be used to some success with audio?
Click to expand...

Thanks for kind words yes it's very interesting but better you can open new thread about Magnetic Amplifiers
and his applications in " Parts " section of the forum ?
This pdf. is with old audio magnetic amplifiers circuits https://www.aes.org/aeshc/pdf/how.the.aes.began/vincent_magnetic-audio-fundamentals.pdf
Edit: short examples with audio MA included at the end of the video
Homemade magnetic amplifiers made from common materials. - YouTube
and now let's back to Tokin SIT's topic in " While they last... " 😀 Have a nice day
 
#891
MartinJohn said:
@ffarges

I have also been considering how to handle the thermal interface for these large electrically connected cases. I have been using Keratherm Kerafol for my builds. The sheets and some shapes are available in our neck of the woods at Conrad (as you probably already know). However I was intrigued by something a bit beefier for the Tokins and indulged in a few Al2O3 insulators from Canada. See attached.
The THF-51S starts to heat up once you get some current flowing >1.5?A. I used a fan on my test heatsink to keep the temperature in the thirties when over 1.8A. Being a €50 part and not easily obtainable I was being observant.
Click to expand...

Hi Martin,

Either you did a perfect job or did not use thermal paste at all, just too clean and neat;-)
I recall Frank mentioned using thermal paste to "fill the gap".
 
#895
60 Watts sounds perfect to me. It will give a chance for my long serving Aleph 5 to have a rest. A point of note, this will make heat sink interfaces more important. I have modeled up one possible option. This would suit the 2SK180 as the leads are on the same side as the mounting face, (not needed for the other Tokin VFets as the leads are on the other side). It could be made from Aluminium and hard anodized thus not requiring surface insulation (the fixings to the heat sink would still need to be isolated) or just isolated as is done at present.
This example is 2" x 1/2" Aluminium flat bar. 100mm (4") long. A point to note is that the mechanical drawing for the 2SK180 shows the original type. The later type (which many of us seem to have) has different size leads.
 

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