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Old 15th November 2009, 02:30 PM   #911
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Quote:
Originally Posted by AndrewT View Post
what is between the chassis base plate and the TF mounting face?
What you listed is not what I can see in the pic.
i see , well there is a small copper leaf and some thermal paste, the nfoto is actually reaaly big if you enlarge it you can see them

Thnax for your remarks.

Nick
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Old 15th November 2009, 02:46 PM   #912
AndrewT is offline AndrewT  Scotland
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I think I see some folded copper sheet, or is it a flattened copper tube?
I think I see a spade connection inserted under the TF.

I think heat conduction through that assembly will be atrocious.

I ask again: WHAT IS BETWEEN THE TF AND THE HEATSINK?
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Old 15th November 2009, 02:57 PM   #913
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It ia copper sheet yes (i used leaf) its foled and flattened.
this spade is in between the copper and it goes to the chassis ground marked chg on the board.

Nick
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Old 15th November 2009, 03:04 PM   #914
AndrewT is offline AndrewT  Scotland
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remove all that rubbish from between the TF and the heatsink.
If the TF is too far off the heatsink to bolt on direct then insert a solid block of aluminium to fill the gap.
The surfaces of the block must be flat and fairly smooth.
The interface between the TF and the Block must be filled with thermal compound as thin as possible with no air and the interface between the block and the heatsink must alsp be filled with a thin layer of thermal compound.
Nothing else should be in there to interfere with the heat conduction from TF to heatsink.

The TF is very poor at conducting heat to the sink, do not make it any worse.

Next time insert the 3886 from the back (bending the legs in the opposite direction) to allow direct mounting to the heatsink.
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Last edited by AndrewT; 15th November 2009 at 03:07 PM.
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Old 15th November 2009, 05:49 PM   #915
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Andrew T ,
thank you for your suggestions !!! i will do so.

I will let you know of the results.
Originally i thought copper sheet between because it will take the heat faster and give it to the aluminum for spreading.
But you know better.

Thanx once more.

Nick
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Old 15th November 2009, 05:52 PM   #916
udailey is offline udailey  United States
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Andrew is right. That spade appears to be under the chip, between chip and heatsink. The chip must be intimately attached to the heatsink.
Also, please use your DMM and measure for DC voltage on your amp outputs that go to your speakers while the thing is playing.
I am worried you burnt your voice coil by inserting DC from the amp into the speaker. It slowly cooks the coil and the speaker will still play while this is happening.
Still, the way that thing is connected to the heatsink just looks wrong. Nothing should connect to that chip besides the board and the sink. Thermal paste only between the two. If you want to ground the sink do that somewhere else, not near the chip or any part of the board that has bare wire/leads.
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Old 15th November 2009, 06:31 PM   #917
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Quote:
Originally Posted by tiglitosa View Post
Originally i thought copper sheet between because it will take the heat faster and give it to the aluminum for spreading.
It will act as spreader only if it's larger than the chip. In your assembly it's not, and it actually makes the heat transfer harder. And inserting the spade inbetween is completely wrong.

Read about measuring DC offset here: Commercial Gainclone kit- building instructions
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Old 15th November 2009, 06:36 PM   #918
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Quote:
Originally Posted by Peter Daniel View Post
It will act as spreader only if it's larger than the chip. In your assembly it's not, and it actually makes the heat transfer harder. And inserting the spade inbetween is completely wrong.

Read about measuring DC offset here: Commercial Gainclone kit- building instructions
Thanx Peter

Yes i got it about the spade, i should have thought of it.
The offset is right thought, 32mv with pot to min, and 71 with pot to max.


Nick
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Old 15th November 2009, 06:41 PM   #919
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by tiglitosa View Post
The offset is...... 32mv with pot to min, and 71 with pot to max.
this indicates that the inputs of the chipamp are not DC blocked from the volume pot.
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Old 15th November 2009, 06:48 PM   #920
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Quote:
Originally Posted by AndrewT View Post
this indicates that the inputs of the chipamp are not DC blocked from the volume pot.
Ok, is there something i should do about it?
According to the reading the Peter suggested, the numebers look logical.
Aren't they?

Nick
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