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Posted (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.

smile.png

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Edited by Victor Chew
Posted

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.

Posted (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 by El_Doug
Posted

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)?

Posted

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.

Posted

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...

Posted (edited)

Well, the second amp powered on without anything blowing up.smile.png

On another note, I will be ordering a Khozmo attenuator. Any more issues with reliability?

Edited by eggil
Posted

Well, the second amp powered on without anything blowing up.smile.png

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

Posted (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 by eggil
Posted

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

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