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Old 16th March 2010, 06:35 PM   #7401
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by hags View Post
I've always had good luck with sil-pads, good heat transfer, easy to use and inexpensive. No complaints here.

I replaced the rectifier bridge in my Acurus A200 with an RFB02 board with discrete components. I used MUR6030s with 2 ohm resistors and 100nf caps.
The difference in sound was noticable and immediate.
Was that due to the snubbers? I don't know.

I have used the same recifier boards with my F5 build. I couldn't be happier with the subjective performance.
I was looking at using Mur3020 ....................
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Old 16th March 2010, 06:43 PM   #7402
hags is offline hags  United States
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Originally Posted by a.wayne View Post
I was looking at using Mur3020 ....................
I bought a bunch of MUR6030s for the quantity discount. I'm able to use them in a variety of applications without worrying about the voltage rating.
I see no downside to the higher voltage/current rated device except maybe voltage drop, for which I haven't noticed a difference.
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Old 16th March 2010, 06:54 PM   #7403
a.wayne is offline a.wayne  United States
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what about Shcottkey diodes ?
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Old 16th March 2010, 08:00 PM   #7404
Renron is offline Renron  United States
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68nF snubbers with MUR860 diodes for the bridge

Ron
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Old 16th March 2010, 08:01 PM   #7405
a.wayne is offline a.wayne  United States
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Are you guys calculating the snubber values ?
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Old 16th March 2010, 08:16 PM   #7406
alazira is offline alazira  United States
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Quote:
Originally Posted by prooptiki View Post
I want to share some more impressions for the f5.

As I said I use large skins, so after many hours the temperature stays to about 40oC, so after reading I started playing with the bias...

0.60v >>> 40oC >>> 65oC (mosfet)
0.71v >>> 43oC >>> 80oC (mosfet after 30min)
Seems like Hags and I are in the minority with the sil-pad. My result when increasing the bias:

1.5v/.91=1.65A : 65C heatsink : 75C mosfet @1hr

In theory the sil-pad should be more effective than mica/goo or Al-Oxide pads/goo, but your actual mileage may vary.
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Old 16th March 2010, 08:36 PM   #7407
hags is offline hags  United States
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Quote:
Originally Posted by alazira View Post
Seems like Hags and I are in the minority with the sil-pad. My result when increasing the bias:

1.5v/.91=1.65A : 65C heatsink : 75C mosfet @1hr

In theory the sil-pad should be more effective than mica/goo or Al-Oxide pads/goo, but your actual mileage may vary.
I don't know about theory but I can tell you I got a little more heat transfer using the sil-pads than the alu-oxide with grease.

Like I said, if I had the sil-pads on hand at the time I would've used them. I didn't so I went with the alu-oxide.

Both work well IMO, I think the sil-pads work slightly better and I like to work with them more so than the grease.
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Old 16th March 2010, 08:37 PM   #7408
Renron is offline Renron  United States
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Long ago in this HUGE thread, Nelson Pass stated that he uses Ultra fast diodes and prefers Mica for insulators.
NO, I don't remember which post #. LOL

Ron
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Old 16th March 2010, 08:41 PM   #7409
cviller is offline cviller  Denmark
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There is a "mica and goo" thread somewhere here on the pass labs forum by papa, where he sums up his findings. AFAIK the result was that sil-pads were fine if the surface was flat, but mica and goo was better if there was surface was not perfect.
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Old 16th March 2010, 09:11 PM   #7410
alazira is offline alazira  United States
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Quote:
Originally Posted by cviller View Post
There is a "mica and goo" thread somewhere here on the pass labs forum by papa, where he sums up his findings. AFAIK the result was that sil-pads were fine if the surface was flat, but mica and goo was better if there was surface was not perfect.
I remember NP's recommendation so I tried it, but instead of silicone goo I used artic silver. The heatsinks ran at 40-45C and didn't think about it for several weeks before checking the mosfet temps and they ranged from 100C to 120C! After removing them I could see that the artic silver did not spread evenly despite my best efforts. That's what I get for trying to be fancy and not using the regular grease which spreads better.

Bottom line is that contact area is perhaps more critical than thermal conductivity or thinness.

The sil-pads need to be torqued down to make sure there are no air pockets, so in this sense they are less forgiving than grease.
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