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Old 14th March 2013, 10:22 AM   #12961
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Join Date: Mar 2011
Location: Tenerife, Canary Islands
Default Soldered before installing in the sink

Quote:
Originally Posted by AudioSan View Post
i would not use the amp until the thermal coupling is corrected.
did you mount the outputs to the sinks before or after you soldered them?
Hi,

I soldered the outputs and then made the hole.... But there is plenty o thermal grease and also mica insulating... Maybe the thermal grease is not good enough?



I am going to wait until the new tranny arrives from antek and is it rated at the stock F5 values of 18v secs.

Regards,

Jorge
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Old 14th March 2013, 10:33 AM   #12962
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Join Date: Feb 2009
that can be the problem. always Mount the outputs before you solder them, to get a good coupling to the sinks.. and there chould not be alot of thermal grease. just a extremly thin layer. thermal grease have a lot of thermal resistance.
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Old 14th March 2013, 10:45 AM   #12963
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Join Date: Mar 2011
Location: Tenerife, Canary Islands
Thumbs up Ok. I will try to fix this...

Quote:
Originally Posted by AudioSan View Post
that can be the problem. always Mount the outputs before you solder them, to get a good coupling to the sinks.. and there chould not be alot of thermal grease. just a extremly thin layer. thermal grease have a lot of thermal resistance.
Hi,

Thanks... I will try to clean the grease and apply a new thin layer. Desoldering the output is a little more complicated but I will see if it can be done without damaging the output....

Regards,

Jorge
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Old 14th March 2013, 01:38 PM   #12964
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Join Date: Jan 2011
Location: Southeastern Pennsylvania
I had excellent results with my F5 using these pads:

http://www.bergquistcompany.com/ther...0S_12.08_E.pdf

And there's no messy grease involved either.
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Old 14th March 2013, 03:10 PM   #12965
sangram is offline sangram  India
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Join Date: Sep 2002
Location: India
Hi

I used mica and grease too, and the first mount delta was 14-15 degrees second mount was 11-12 degrees with about 35W (I ran it a bit hard because I had good sinks).

I used a razor blade to separate the sheets of mica and *very carefully* used the thinnest I could find. I also used Arctic Cooling MX-2 because regular grease is quite bad over here, and I used very, very little on each side of the mica. It wasn't a layer as much as a kiss.

The point is get it so thin that it is just filling the air gaps at a microscopic level. The actual heat conduction is by direct physical contact. You don't want the surfaces to stay insulated from each other by the grease, which is the problem with too much of it.

You can also try a bar over the outputs and torque it down to squeeze out every last bit of contact patch, this will help a lot with single-hole devices being asked to deliver so much.

Good Luck.

Quote:
Originally Posted by jcastellano View Post
Hi,

I soldered the outputs and then made the hole.... But there is plenty o thermal grease and also mica insulating... Maybe the thermal grease is not good enough?



I am going to wait until the new tranny arrives from antek and is it rated at the stock F5 values of 18v secs.

Regards,

Jorge
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Old 14th March 2013, 03:43 PM   #12966
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Join Date: Feb 2009
Quote:
Originally Posted by sangram View Post
Hi

I used mica and grease too, and the first mount delta was 14-15 degrees second mount was 11-12 degrees with about 35W (I ran it a bit hard because I had good sinks).

I used a razor blade to separate the sheets of mica and *very carefully* used the thinnest I could find. I also used Arctic Cooling MX-2 because regular grease is quite bad over here, and I used very, very little on each side of the mica. It wasn't a layer as much as a kiss.

The point is get it so thin that it is just filling the air gaps at a microscopic level. The actual heat conduction is by direct physical contact. You don't want the surfaces to stay insulated from each other by the grease, which is the problem with too much of it.

You can also try a bar over the outputs and torque it down to squeeze out every last bit of contact patch, this will help a lot with single-hole devices being asked to deliver so much.

Good Luck.
i use MX2 as well a very good grease and Nice price
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Old 15th March 2013, 01:41 PM   #12967
diyAudio Member
 
Join Date: May 2012
Hi guys!

Im collecting parts for an F5 now. Most is in the mail at the moment. Painful.
Still, I have not decided how big/many resistors I should have in the psu.
I have a 400va 2x18v transformer, and 14x6800uf caps. And I have a macbook, so I cannot use the duncan software.

Any suggestions?
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Old 15th March 2013, 02:08 PM   #12968
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Join Date: Feb 2005
Depending on the quality of the caps, suggest 6,800uF - 0.1R - 2 x 6,800uF for each rail, per channel (ie, 12 of those 6,800uF caps in tota) - if only the 1 pair of 18v windings, still use a seperate 4 diode bridge for each channel.
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Old 15th March 2013, 02:13 PM   #12969
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Join Date: Oct 2009
Location: Brunei
Or use duncan's under crossover on your Mac... That's what i do
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TDA1541a-S2 / 6072a / MediaplayerDac -- Michell Gyrodec -- Aikido Preamp -- Pass F5 -- Audio Physic Tempo 2SE -- Yamamura Cabling
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Old 15th March 2013, 10:04 PM   #12970
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Join Date: Sep 2006
Location: Santa Rosa Beach, FL
Quote:
Originally Posted by jcastellano View Post
Hi,

Thanks... I will try to clean the grease and apply a new thin layer. Desoldering the output is a little more complicated but I will see if it can be done without damaging the output....

Regards,

Jorge
This might help. You don't necessarily have to REMOVE the output transistors. If you already have them mounted, then simultaneously heat all three of the PCB solder pads for each MOSFET (you might have to use two soldering irons, and enlist the help of a friend). The trick is to "reflow" the existing solder, to allow the MOSFET to seat itself on the heatsink/grease while all three transistor pads are molten.

Don't remove the MOSFET unless you must--it's a lot easier just to reflow the existing solder....and it will save the wear and tear on the PCB pads.
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