Burning temp. of Mj11015 and MJ11016

[darkm4n]

I buyed last week some kit amp's that are powered by
2 x Mj11015 and 2 x Mj11016 ( one board )

They get hot .. aprox. 55 C
What is the maximum temp. those output drives could support ?

Thanks

[Jan Dupont]

You find the datasheet here:
http://www.onsemi.com/pub/Collateral/MJ11012-D.PDF

55 C is nothing for a Power Amp, but normally you would try to avoid anything over 70 C as the temperature limits the safe maximum Current through the transistor..........

[darkm4n]

Thank's

I have 2 monstrous coolers for those output .. so it souldn't pass the 40 C barrier .

[Jan Dupont]

With coolers (if you can/will accept the noise) it easy to secure a low temperature.... Just use some kind of temperature sensing, so they fans won't start, when you are playing at low volume

[sully]

ACD has good advice..

Is it the transistor case that is getting hot, or the heatsink?

Absolute temp will also depend on the circuit, and the way the chips handle secondary breakdown under power..

Cooler is always better, double lifetime every 10 C drop.

Cheers, John

[darkm4n]

The transistor case is getting hot , the heatsink is pretty hot too ..
I could put my hand on it .. i stick it and i didn't burn my finger ... i only got shocked by the 40 V that the amplfier power supply give ..

If i gonna add some fan's , how should i put them ?

I want to put ( one on each board ) them inside the case ( with hold outside ) to suck air from the case and throw it out ( i will place them over the output transistors )

And two on each heatsink to suck air from it .

How should i put them ? To suck air from the case ? Or the suck air from outside and throw it in the case ?

Thanks , Mihai .

[sully]

The fans should be able to direct flow alongside the fins, in the direction of the fins. If you blow air across those as mounted, the airflow will be very ineffective.

John

[darkm4n]

How should i put the one above the transistors ? to suck ? or to thorow air out ?

[sully]

Directly above them, I would blow the air onto the devices..I think that will be a more focussed cooling stream..but, that will still be an ineffective use of the fans..

I would prefer the fans either over the fins, or under, blowing across them. that is better.

Cheers, John.

PS..gotta bolt..happy holidays, good luck.

[darkm4n]

Anyone have any idee how to mount the fans on the fins ? The fins are not so big .. so ........... i can't put a fan on them .......

Thanks....