B22 Mosfets questions
Sep 14, 2009 at 2:24 AM Thread Starter Post #1 of 16

deathg0d

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Hi due to the availability of choices for casing here in my country, i am trying to minimize the size of assembling the boards into a case. thus i have this idea but not sure if it gonna work or deteriorate b22 performance so i hope some pros here could advise me on it.

well simply to say, i am thinking to use wires to extend the mosfets and mount the four mosfets q21-q24 onto the case bottom instead of mounting them on the board. this is a pic of my intended setup.

anyone kind help will be very much appreciated.
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Sep 14, 2009 at 3:12 AM Post #3 of 16

deathg0d

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Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif
Generally not recommended, plus, you must have a very heavy-duty chassis if you plan to use it as one large heatsink for all MOSFETs.


if am plan to get something from par metal and add external huge heatsink to both side of the chasis?
 
Sep 14, 2009 at 4:33 AM Post #4 of 16

ShinyFalcon

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One MOSFET already gets hot enough as it is... making it do four times the work would probably melt the poor thing. Also wouldn't the four channels get mixed together if you do this?

Edit: or are you trying to tie sixteen MOSFETs to one heatsink? It would be pretty unstable I would say...
 
Sep 14, 2009 at 4:45 AM Post #5 of 16

amb

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It is not advisable to use wires to extend the MOSFETs offboard. Wires have inductance, and that inductance will form an LC resonant circuit with the gate capacitance in the MOSFET. That could make the amp unstable.
 
Sep 14, 2009 at 8:26 AM Post #7 of 16

amb

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Quote:

Originally Posted by deathg0d /img/forum/go_quote.gif
can the board with heatsink place on top of each other? with sufficient gap clearance between them?


You'd need a pretty big gap... or heat would get trapped.
 
Sep 14, 2009 at 8:50 AM Post #8 of 16

deathg0d

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Quote:

Originally Posted by amb /img/forum/go_quote.gif
You'd need a pretty big gap... or heat would get trapped.


arrrrggghh~~~ anyone can provide me some advises??? i am nearly going mad...
1st i got adventorous and gotten myself 5 boards, but later found out that singapore has almost nil workshop provding custom chasis fabrication services and thus i am stuck with getting from par-metal but getting a big size chasis will kill me on the shipping cost.....
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Sep 14, 2009 at 9:15 AM Post #9 of 16

amb

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deathg0d, you should get creative. Cases can be DIY'ed too. Look in the β22 website gallery and the "Post pics of your builds" thread for ideas.
 
Sep 14, 2009 at 9:32 AM Post #10 of 16

deathg0d

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Quote:

Originally Posted by amb /img/forum/go_quote.gif
deathg0d, you should get creative. Cases can be DIY'ed too. Look in the β22 website gallery and the "Post pics of your builds" thread for ideas.


well amb, i have been until now... i have drawn and redo countless time in autocad how to get the boards place nicely... however i guess due to the fact that i am bent on getting metal casing which sg seem to have a shortage with, i am quite in a fix.

my situation now is as below.

a) using extended shaft for DACT CT2 - cant find any reseller here. if i buy from oversea, i have problems of getting the L shape plate to mount CT2. if i order the L shape plate from oversea as well, i dont think i can make mistakes on the the dimensioning thus if i get wrong, i will have a difficult time getting it correct.

b) if i mount the CT2 directly on the front, i do not have enough space unless i can get custom cut sizing.

well.......... thinking.....
 
Sep 14, 2009 at 10:24 AM Post #11 of 16

digger945

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I purchased my DACT shaft extender from an ebay seller in Hong Kong.
Keep in mind that the DACT shaft is 6mm(.2362), not 1/4"(.250).
I think I remember a shaft and/or coupler that was 6mm on one end and 1/4" on the other, giving you the option to use a 1/4" panel bearing and 1/4" volume knob.
 
Sep 14, 2009 at 2:24 PM Post #14 of 16

deathg0d

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bros, the problem is i do not have drills with me. or simply to say i do not have e necessary tools to drill holes... that is why i am in such a diemma. singapore is a very restricted small country.... how sad...
 
Sep 14, 2009 at 2:25 PM Post #15 of 16

deathg0d

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i have never see the actual parts before until i get hold of them, thus dimensions like shafts, aluminium plates thickness... i am hitting blindly on autocad base on my presumptions and maybe old data specs from manudacturers.... the possibilities of me going wrong is very high
 

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