Is this method of heat sinking a good idea? N00b question ahead... - Page 2 - diyAudio
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Old 2nd May 2012, 11:47 AM   #11
AndrewT is offline AndrewT  Scotland
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Tell McBob.
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Old 2nd May 2012, 03:52 PM   #12
bcmbob is offline bcmbob  United States
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I complete understand and really don't expect completely accurate readings at this price. What prompted me to get it was two situations:

1. On a BPW-150 project one of the caps smoked after about 30 seconds on the third try for initial power-up.

2: The transformer for a JC-2 preamp got hot enough to fry eggs due to incorrect wiring. I didn't notice it till some fumes and smoke got my attention.

Now - my method for initial power-up is to use both a dim bulb tester and rapidly target all components with the laser looking for any heat rise - with one finger on the AC switch. It is quite easy to identify the difference between ambient and hot.

My low-tech calibration method is simply to read three or four things I know are at room temperature for consistency.

So I'm in full agreement that a low cost tool like this can be useful only if one stays within its limitations. This one helps me un-clench my toes more quickly when I throw the power switch.
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Last edited by bcmbob; 2nd May 2012 at 04:11 PM.
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Old 2nd May 2012, 04:59 PM   #13
Simon B is offline Simon B  United Kingdom
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It doesn't look terrible, but it could certainly be improved.

The case is almost certainly mild steel, it's a lot cheaper than Aluminium, but contrary to Conrad, I'd say that with sufficient contact area and perimeter length of aluminium bracket, it's actually a very useful part of the heatsinking.

If you can, make a larger, thicker aluminium bracket to replace the existing one, that should help reliability, which practice amps have a rather poor track record on, often for this exact reason.

The components on the board are quite close to the active devices, so fitting additional heatsinks might require some filing to avoid fouling and shorts, and their thickness will mandate moving the bracket's mounting holes - but you were going to make another anyway right?.

Be careful to replace the mica insulator, don't be tempted to use a silicone pad, they add thermal resistance. Use a thin even smear of heatsink compound, on the device, both sides of the mica insulators, the additional heatsink, front and back, the aluminium bracket, where it meets the new heatsink and where it joins the chassis.

Attached are some pictures of a small amp I recently repaired. The existing heatsinking was woefully inadequate, the bent aluminium bracket was thin, about 1mm, there was a thermal bottleneck around the perimeter of the devices. An additional heatsink was added to each device, getting some heat straight out into the air, and themal contact with the aluminium bracket much improved. Under full load the steel chassis became quite warm - heat transfer to it had also been improved.
Attached Images
File Type: jpg Ashdown before.jpg (48.1 KB, 40 views)
File Type: jpg Ashdown after.jpg (60.7 KB, 39 views)
File Type: jpg Heatsink.jpg (14.3 KB, 40 views)
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Old 2nd May 2012, 05:13 PM   #14
bcmbob is offline bcmbob  United States
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Here's the L channel I was looking for when I posted the pic in #4. It is 2" x 2" X 1/8". The fins are from a PC HS cut in half and could be attached on either side of the vertical leg.
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File Type: jpg 20120502_120150.jpg (676.9 KB, 32 views)
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Old 2nd May 2012, 05:31 PM   #15
Simon B is offline Simon B  United Kingdom
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Quote:
Originally Posted by bcmbob View Post
......2" x 2" x 1/8".........fins are from a PC HS cut in half ........

That's the way to do it!

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Old 2nd May 2012, 05:47 PM   #16
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@ Bob M: A thermographic camera is faster than the IR thermometer. You can diy one by removing the IR supressor-filter from an old digital photographic camera.
Some Sony DSC-V series have an IR mode.
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