operating temperature for Aleph

[Phill]

Hello

the radiators of my Aleph 5 are a little small ,and I can't any more modify them
with an ambient temperature of 20°C, the radiators are with 57° .
but in summer, it makes 30°, ==> 67°C.
Which is the tolerance? before it leaves in smoke
and I would like well that the components last a long time!
thanks
Phill

[GRollins]

Nelson has a rule of thumb (so to speak) about how long you can leave your hand on the heatsink before you have to snatch it away with a squeak of pain. I don't remember the actual sequence, but I'm sure five other people will post it before I finish typing this post.
I'm a little more conservative than Nelson regarding heat. I like to be able to leave my hand on the heatsink forever. In a situation such as yours, I'd recommend fans.
Or you could go to water cooling...


Grey

[Eric]

Grey, is this what you were thinking of?

Nelson has previously indicated the following:

Blimey hot is 10 sec hands on = 45c
Crikey hot is 5 seconds = 50c
Bloody hot is 2 seconds = 55c
X*?@! is 60c

Keep output mosfets at 75-80c max

[Phill]

Thank you

there are probes of temperature which function very well!

My grandfather was a baker....
it left the breads the furnace with its hands...
and I make similar...it is true!
it is not good for my fets...


a temperature lower than 45 °C would be well, no ?

Phill

[wuffwaff]

Hi,

50-60°C for the heatsinks is OK. You could also measure directly on top of the fets (the plastic). This is a bit difficult but normally if you measure below 80°C you don´t need to worry.
Fets have different feelings about what´s hot or not as we humans.

For verry hot summerdays you can always put in a switch to reduce bias by 10-10%

William

[Phill]

Originally posted by wuffwaff
Hi,

For verry hot summerdays you can always put in a switch to reduce bias by 10-10%

William

thank you, it is a good idea!

Phill

[mastertech]

Guys i have tempareture problem
the heatsink temperature is at arount mid 40degreesC but
the probe on the plastic body of the device is reaching 100degreeaC and rising when i hit the off switch

whats the problem, i dont use heatsink compound
should i screw the device tighter, or is it something else

[lumanauw]

whats the problem, i dont use heatsink compound

For average DIYing, this could be the problem (unless you have other kind of method to ensure maximum contact between transistor's plate with the heatsink). If you look under the microscope, the heatsink surface is not flat at all. It's like "mountains" and "valleys", where the ones that can contact the transistors plate body is only the highest "mountains". It is very few contact points compared to the area of the whole transistor plate.
Putting heatsink compound is the most effective way to make maximum contact between transistor body plate and heatsink surface. Using grey rubber silicon insulator makes the look neater, but I still think the heatsink compound is better (but looks messier).

You must have known this, because you're a CLASS A SPECIALIST. And since you don't use heatsink compound, you must be using some kind of advanced technique. Could you share what method do you use to ensure maximum heat tranfer from transistor's body to the heatsink, that do not use heatsink compound? You CNC-micro grinding all the contacting surfaces?

[mastertech]

HI lumanauw

thanks a lot , ill try putting some heatsink compound on all sides
of contact and see what happens

i am still learning

one more thing which is better regular washer or silicon rubber
this will improve heat transfer to heatsink dont you think?

thank you so much lumanauw

cheers

[iwahn]

Phill, paint your heatsinks black.

Regards