Cooling Angel

[tab30]

Hello,

this picture is my "first version" of the Holton SymAmp.

The cooling-angel on wich the output Fet's mounted is 3mm thick.

Is it enought ?
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For example the Alps modules have an 6mm thick one.

And holton say's in his manual between 3mm and 5mm

If I touch the Fet's ( driving the amp with an output amplitude of about 25 V and RL = 4 ohm ) they feel realy hot, if you hold your fingers longer than about 2 sec. it hurt.

- The black heat sink is only temporarily, it is too smal but even if the heatsink is at beginning quite cold I mean the Fets are too hot-warm.

will more thick angel improve the cooling significant ?


Greetings Andi

[Andypairo]

Hello,
nice work you've done!
Did you consider mounting the PCB direct to the heatsink without angles?

Be careful on mosfet matching also - keep an eye on the voltage on the source resistor to see if they share the current evenly, otherwise one or some will draw much more current than the others. I experienced that

The pic shows how I did the thing

Cheers

Andrea

[Magura]

To fully utilize the heatsink, the angle must be as thick as the base of the heatsink. I guesstimated the base to be around 10mm thick, if thats so 3 mm is waaay too thin.


Magura

[tab30]

@ Andypairo

Hello, yes in fact i considered, mounting the devices direct on the heatsink.

But prefer to have an completed modul, wich I'm more flexibly.

I matched the Fet's within 40mV gate threshold, with Holtons method.
It was interesting, the 9240 was easy to get 4 one with near gate threshold ( easy within 10mV ) but the 240 spread much more.

( I have 40 piece 9240 and 40 piece 240 meassured )


@ Magura,

Hello,

I think the angel can be a bit thin than the back of the heat sink.Because he must conducte the heat energy only few mm-1cm but the heatsink have to spread it over an lager area.

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well in the next day's I'll get my Temperatur sensor's then I will archive better results than getting by touching the things with my fingers :-)

by the way the Temp sensors I found are interesting ones, cheap and easy tu use. LM 35 ; and LM 335

[runebivrin]

How hot is the cooling angle? If the angle is relatively cool, but the FET:s are hot, it would indicate that there is a problem with heat transfer between transistors and angle.

Rune

[tab30]

@ Runebivrin,


Hi,


betwen the Fet's and the side of the angel the Fet's are lieing on is no noticeable temperatur difference.

But betwen the side of the angel at the heat sink and the one with the Fet's is an noticeable difference. But not VERY hight.

The problem is my fingertip not very exactly :-)...

Within the next day's I will populate temperatures here.


I hope you all have the same sunny day,

Andi

[tab30]

@ Andypairo

I jus measured the voltage drop at the source resistors it is within about 100mV at all 0,6 V by driving the amp with an 1KHz sin near cliping.


warm regards :-)

Andi

[cabbagerat]

I wish I had a cooling angel - would save me money on big heatsinks

[tab30]

Are you still using Heatsinks ???? :-)

[Sonyx]

in the first picture it looks as though you havent used thermal paste between the mica pads and the output devices, and between the mica pads and the cooling 'angel'