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Old 12th February 2002, 06:50 PM   #11
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Round up the usual suspects. Start with the
Zeners.
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Old 12th February 2002, 07:15 PM   #12
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Grey,

normally kapton insulators have a significantly lower thermal resistance (0,07 K/W) than mica + silicon grease. Why dont you like them? (Please dont give me a good reason cause there are about 24 lying around here waiting to get used in my Aleph)

william
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Old 13th February 2002, 02:30 AM   #13
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Quote:
Originally posted by wuffwaff
Grey,

normally kapton insulators have a significantly lower thermal resistance (0,07 K/W)
from memory, that's for hockey puck style mounting @ very high pressure.
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Old 13th February 2002, 02:38 AM   #14
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Hmmm...
You ask for a reason, but <i>not</i> a good one. Why didn't you set me an easy task, like cleaning the Stygian stables?
Uh, well, okay, how 'bout this? One of my degrees is in geology and I find mica (biotite, muscovite, et al...) inherently more interesting than a man-made material.
Not good enough, huh?
Okay, well, from a tree-hugger's perspective, mica is a natural material that won't hurt bunny rabbits, box turtles, or kangaroos. The research on pandas isn't in yet, so they'll just have to take their chances.
Ah, fooey, go for the jugular...
I'm a naturally suspicious, cynical critter who feels that every new technology is guilty until proven innocent. I've heard too many people complaining about problems with 'em. In my view, if your cooling is so marginal that the 1 bazillionth of a degree difference in cooling between mica and Kapton is all that stands betwixt you and a puddle of slag that used to be an amplifier, you need bigger heatsinks.

Besides, you can see through mica...and we all know that transparency counts in audio.

Grey
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Old 13th February 2002, 10:09 AM   #15
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Default static

Scott,

Always check the least obvious..

You mentioned you still get static after changing the insulation.
washers.. but disappears after a little while.

The problem could be heat or a fault mechanical connection

1. Have you metered the insulation for each hexfet (with hot and cold heats), there could be a problems with the mounting bolts on the hexfets.

2. Are the heat sinks and the chassis earthed to the mains plug ground(not the 0 volt ground which should only be in connection with the chassis at one point).

Test for zero ohms for the faulty channel. or tighten any bolts or other offending hardware.

I have found that if the heat sink is floating you get static in the output .

3. The power supply.

If the Led flickers either the positive rail or output are shifting for some reason obviously.

This could be due to loose screws in your power filter capacitors for that channel or a dry joint somewhere(I had this problem).

4. The fact that you only have this problem in one channel suggests that all things being equal it is not component failure if everthing was previous replaced.

(But not with standing this one of the capacitors (or zeners) could be routed so replace if all else fails.. capacitors are strange and they can be intermitently faultly and change with heat).

I hope these suggestions help at least solve the problem by process of elimination.

regards

macka
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Old 13th February 2002, 06:23 PM   #16
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Grey,

thank you very much for this very nice reason: I will use the ones Ive got and buy mica again for the next amp!
This will save all the nice little bunnys that live here (no kangeroos nor koalas Im afraid)

william
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