Kristian's Aleph 2,3,4,5 series PCBs

[trigon]

Hi.

For Kristian's Aleph 2,3,4,5 series PCBs, here is an idea or suggestion of haw can you
place the 240s or 244s on effective way and easy placement and replacement.
I am just looking for the big wide sil-pad or mica insulator that I can use for that aluminum profile
so that I can isolate the heatsink from the profile.
In this way Transistors are mounted directly on the aluminum what further improves heat transfer.

Any comments?

[Peter Daniel]

In one way it's good in another it's not. Where did you get those bars?

If you got them for free and got bigger than usual heat sinks, it's all right.

Otherwise there are better ways to mount those FETs. But you know my POV anyway.

[trigon]

Hi Peter.

My friend did it for me and heatsinks are you know, kind of big, 4 of them for 2 monoblocks of Aleph 4. Here they are. I've got new camera and still fighting with size of images

Those bars are actually big, they should do the job.

Here it is.

[trigon]

Mounting holes. M4

Any idea for silpad big enough for this bar.

[daatkins]

Hello Trigon,
That's a good idea - the larger surface area between the mounting bar and heatsink will give a lower thermal impedance (case to HS) than isolating the MOSFETs individually. I did something similar on my Hiraga Classe A.

You can buy large sheets of insulating material which the user then cuts to the size they need. For example, Farnell item number 279900 is a 300mm x 300mm sheet with a quoted thermal resistance of 0.23'C/W (I think this is per cm^2 of area, although this isn't specified). Price is just under £7 - about $10.

Nice one,
David

[trigon]

Actually I was thinking not to have MOSFETs individually isolated as they have drains short-connected anyway (Aleph 4). What I was referring to is to isolate the whole bar in which case transistor dissipate directly on the bar which increase the silicone cooling plate so that junction temperature is lower. Thanks for the info.

Trigon

[UrSv]

I don't know if that is what Farnell stocks but Alutronic sheets.

http://www.alutronic.de/e/aluDB.php?...ber+reinforced

You don't think it is a bit risky to mount them without insulation? The risk of connecting any of the Drains to the mounting bar is quite high meaning that the whole bar is your Drains. Oviously I know you are using silpads to transfer the heat from the bar to the sink/chassis but they will most likely be electrically connected through the screws which would need insulation as well which I can not see in your pictures. I suspect this would make it hard to use the required torque to attach it to the sink unless using lots of screws.

Otherwise it looks really good. Should be a nice amp..

/UrSv

[trigon]

Hi UrSv

Yes, good point I will be using isolating tubes for the bar's screws.

Thanks

Trigon

[daatkins]

Trigon,
I think you misread my post - I'm agreeing with you! Insulating the bar from the main heatsink would give better heat transfer than isolating the MOSFETs individually with the bar connected directly to the HS.

I also missed the bolt issue. Plastic M4-sized bushes are probably available though.

Nice one,
David.

[trigon]

daatkins

I think you misread my post - I'm agreeing with you! Insulating the bar from the main heatsink would give better heat transfer than isolating the MOSFETs individually with the bar connected directly to the HS

Uppsss, I guess you are right, sorry

UrSv ; daatkins

I also missed the bolt issue. Plastic M4-sized bushes are probably available though.

As I still have not drilled the holles on the heatsink side I think that I should replaced the screws with M3 and use Plastic M3-sized bushes , if I don't get M4s. Or maybe I can make some M4 bushes of some kind of hard insulating material, like kind of fibreglass or soo + some nice tubing. (hand made bushes )

Thanks guys for the tips

Trigon