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Old 1st June 2003, 04:24 PM   #1
jazzy is offline jazzy  Slovenia
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Default My baby is HOT!!

My baby is hot ,very hot too hot for me.
I can't even touch her.
Perhaps she need a bigger...... ...heatsink??
OK anyhow:
łTEST A5 monoblocks (without exotic parts- resis., semiconduct., caps.ect) in sort-of test enclosures.
- PCB own design
- Heatsink dimensions 30 X 12 X 4 cm
PSU:
- 2 X 35A/200V Bridge
- 2 X 27 V 350W Trann. + CL 70
- 2 X 50kuF this moment without Pi filter ( 2,2mH)
- 2X 36 V Rail
Power Mosfet resistor:
- 2 X 2,2 Ohm 2W Noninduct. parallel ( 0,575 V )
Output resistors:
- 8 X 1 Ohm 1W Noninduct. parallel.

Tomorrow I will check HS. temp with termometer and find possible oscilation with scope!

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Old 1st June 2003, 04:26 PM   #2
jazzy is offline jazzy  Slovenia
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Default Hot baby pic .

More pics.!!
jazzy
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Old 1st June 2003, 04:35 PM   #3
jazzy is offline jazzy  Slovenia
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Default Hot baby pics.

jazzy
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Old 1st June 2003, 04:37 PM   #4
jazzy is offline jazzy  Slovenia
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Default Last pics!

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Old 1st June 2003, 07:01 PM   #5
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How high did you set the bias?
And, how hot does your amp run exactly?
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Old 1st June 2003, 07:05 PM   #6
moe29 is offline moe29  United States
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sinks do look a little small... put a fan on them or find a bigger
sink. FET spacing looks to small too. It would be nice if you had
2 more sinks just like that... split your fets between them with
more spacing...

the quality of your work is very nice though!

heat sinks... can never be too big!!


good luck,
m.
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Old 1st June 2003, 11:05 PM   #7
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I would split up those devices and double your present heatsinks.....at least.....
Bacon and Eggs ala Aleph honey?
MArk
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Old 2nd June 2003, 03:04 AM   #8
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On some tests I did last year on heatsinks I found a fan would improve the heatsink perfrmance by a factor of 6. Yep, six times as good. I have dumped as much as 350 watts onto a 100mm x 100mm sink with a 90mm fan going full blast, but that was really the outer limits.
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Old 2nd June 2003, 03:25 AM   #9
jwb is offline jwb  United States
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Yeah, of course. Fans are awesome. But more importantly I see a lot of designs on this site with the transistors all in a line. This is a huge waste of the heatsink's ability. Space them evenly on the surface of the sink, and you will get much better performance.

The transistors in the picture above are WAY too close together. Most of this heatsink is wasted.
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Old 2nd June 2003, 10:07 AM   #10
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Quote:
Originally posted by jwb
Yeah, of course. Fans are awesome. But more importantly I see a lot of designs on this site with the transistors all in a line. This is a huge waste of the heatsink's ability. Space them evenly on the surface of the sink, and you will get much better performance.

The transistors in the picture above are WAY too close together. Most of this heatsink is wasted.

I did some testing with thermal calculation software and there almost no difference in placing the mosfets when you have thick enough back plate (>10mm will do) . There was only a 4 degree difference between the mosfets in placing them in line and all spread around... hardly worth the trouble in wiring, buy more heatsink to compensate this!

I did some measurements on my running Aleph 4 and there is almost no difference between the left, the top the back and bottom when all is in balance after 60 minutes of running... All is hot!

Ofcourse his mosfets are a bit too close and his heatsink look too small...

Edwin
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