Victor Chew Posted April 9, 2012 Report Share Posted April 9, 2012 (edited) It needs a wood knob! Making an ebony knob that big without cracking could be quite a challenge. I will try with wood block pictured. Don't know what wood it is but is's so hard that when I cut it at the carpenter's shop smoke started appearing between the blades and the wood even though I was not pulling hard at the cutter travel. Don't know if I will succeed. Edited April 9, 2012 by Victor Chew Quote Link to comment Share on other sites More sharing options...
deepak Posted April 12, 2012 Report Share Posted April 12, 2012 2SC4686 back in stock at Mouser Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted April 12, 2012 Author Report Share Posted April 12, 2012 I did a lifetime buy for me, and they already shipped. Stock up now, or be sorry. Quote Link to comment Share on other sites More sharing options...
El_Doug Posted April 12, 2012 Report Share Posted April 12, 2012 Just wish I had a working PSU for testing... sigh Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted April 12, 2012 Author Report Share Posted April 12, 2012 The 4686a parts are already isolated, so they don't Need the ceramic insulators Quote Link to comment Share on other sites More sharing options...
El_Doug Posted April 12, 2012 Report Share Posted April 12, 2012 I know, but it helped make the spacing even The 4686a parts are already isolated, so they don't Need the ceramic insulators Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted April 12, 2012 Report Share Posted April 12, 2012 I has a sad for your die temps. Plastic parts are already disadvantaged compared to their metal brethren. Quote Link to comment Share on other sites More sharing options...
El_Doug Posted April 13, 2012 Report Share Posted April 13, 2012 no locktite yet (since I'm untested), so I'll just yank them out thanks for letting me know Quote Link to comment Share on other sites More sharing options...
n3rdling Posted April 13, 2012 Report Share Posted April 13, 2012 Thanks for the heads up deepak, finally got mine ordered Doug what chassis are you using? Quote Link to comment Share on other sites More sharing options...
El_Doug Posted April 13, 2012 Report Share Posted April 13, 2012 Using the vt4c large chassis Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted April 13, 2012 Author Report Share Posted April 13, 2012 And you still need some thermal grease, or the silicon impregnated washers on the 4686a. Same thing on the ixys part, thermal grease is better for that and it goes on both sides of the ceramic. Just a little is all you need. Any more than that makes a mess. And nothing electrically conductive either, like arctic silver crap. If its not white, you don't want to use it. Quote Link to comment Share on other sites More sharing options...
El_Doug Posted April 13, 2012 Report Share Posted April 13, 2012 (edited) Already have incorporated thermal paste (and yes, it is white). Glad to see I wasnt being over the top by doing so! edit: in fact, you can see the little tube of it in left of my photo Edited April 13, 2012 by El_Doug Quote Link to comment Share on other sites More sharing options...
johnwmclean Posted April 13, 2012 Report Share Posted April 13, 2012 Just for the dummies and to clarify... The 4686a sand preferably should not be used with al oxide insulators, as the package would be thermally compromised? All that is required is a little thermal paste (white stuff)? Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted April 13, 2012 Author Report Share Posted April 13, 2012 Correct. I have tested the plastic on the 4686a (collector to sheet of metal underneith it, bolted tight) to about 2kv before breakdown. You can put the aluminum oxide insulator in, but it adds unnecessary thermal resistance and you don't need the voltage protection. Quote Link to comment Share on other sites More sharing options...
johnwmclean Posted April 13, 2012 Report Share Posted April 13, 2012 (edited) Thanks Kevin. El_Doug your build looks great, fingers crossed your psu is up and running soon. Edited April 13, 2012 by johnwmclean 1 Quote Link to comment Share on other sites More sharing options...
johnwmclean Posted April 14, 2012 Report Share Posted April 14, 2012 I’ve tested by psu, aiming for a +/-450V output, the result is +/-457V, will this be ok for the 2SA1968’s? I have some 430K’s on hand, that should bring it down to +/- 442V, what do you think... Quote Link to comment Share on other sites More sharing options...
spritzer Posted April 14, 2012 Report Share Posted April 14, 2012 It will be fine. The 900V rating on the 1968's is conservative as most units surpass it by quite a margin. Quote Link to comment Share on other sites More sharing options...
johnwmclean Posted April 14, 2012 Report Share Posted April 14, 2012 Thanks spritzer, that is good to know and saves me tampering. Quote Link to comment Share on other sites More sharing options...
eggil Posted April 16, 2012 Report Share Posted April 16, 2012 (edited) Well, the second amp powered on without anything blowing up. On another note, I will be ordering a Khozmo attenuator. Any more issues with reliability? Edited April 16, 2012 by eggil Quote Link to comment Share on other sites More sharing options...
Victor Chew Posted April 16, 2012 Report Share Posted April 16, 2012 Congratulations eggil. Quote Link to comment Share on other sites More sharing options...
spritzer Posted April 16, 2012 Report Share Posted April 16, 2012 I would certainly measure each step on every gang of the Khozmo. Same thing with the Dact's and all other steppers. Quote Link to comment Share on other sites More sharing options...
justin Posted April 16, 2012 Report Share Posted April 16, 2012 Well, the second amp powered on without anything blowing up. On another note, I will be ordering a Khozmo attenuator. Any more issues with reliability? let me know if you get an email reply from them. and interested in your comment on "more" issues with reliability Quote Link to comment Share on other sites More sharing options...
eggil Posted April 16, 2012 Report Share Posted April 16, 2012 (edited) I did get an email from them within 24 hours when asking for information yesterday. They look very nice and I did not mean to imply anything. The only thing I know about them is what people have commented here and somewhere else. There are a couple of comments in this thread too. Edited April 16, 2012 by eggil Quote Link to comment Share on other sites More sharing options...
deepak Posted April 16, 2012 Report Share Posted April 16, 2012 I did get an email from them within 24 hours when asking for information yesterday. They look very nice and I did not mean to imply anything. The only thing I know about them is what people have commented here and somewhere else. There are a couple of comments in this thread too. Why not use a quad (or 2 ch) TKD pot? Then you aren't left worrying about the long term reliability of an unknown mechanical switch Quote Link to comment Share on other sites More sharing options...
eggil Posted April 17, 2012 Report Share Posted April 17, 2012 I think Horio and Cobra Kai have used the Khozmo. IIRC, Horio used the 10K. That's is probably the one I'll get. Quote Link to comment Share on other sites More sharing options...
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