Just finished assembling two PA150 (3x LM3886) boards, inside a recycled mini PC case. Already turned on, and measured rails: around +/- 38 DCV. Still in the safe area, although not that safe... Offset around 12mV.
Next, listening impressions.
Next, listening impressions.
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That's a small heatsink for three chipamp channels.
The fan is set up to blow into the end plate of the first cooling fin. And the top of the fan misses the fins, to blow air around the inside of the casing.
The fan should be set up to blow THROUGH the gaps between the fins.
Are the fins slotted?
Enclose the sinks so that the air from the fan blows through and does not escape/bypass the sinks.
The fan is set up to blow into the end plate of the first cooling fin. And the top of the fan misses the fins, to blow air around the inside of the casing.
The fan should be set up to blow THROUGH the gaps between the fins.
Are the fins slotted?
Enclose the sinks so that the air from the fan blows through and does not escape/bypass the sinks.
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Thank you very much.
Those sinks are from an old Compaq Deskpro 2000 Pentium 133 computer.
This amp will run at low/mid levels for a short period of time (mostly voice and ambient music), at 8 ohms load.
The look like large CPU heat sinks to me. That should be OK assuming the fan provides enough airflow.
Have a look at the second picture in Post #1. The picture that shows the heat sink at an angle. It's pretty obvious what's going on.
I do agree that some ducting to control the flow of air would improve the cooling. Whether it's needed is another story. One could run the amp at 1/2 the rated output power on both channels while monitoring the heat sink temperature (and the THD). That'd be the worst case power dissipation scenario. For music reproduction, the dissipated power is usually considerably less.
Tom
Wow! That's some really beautiful work. I would love a bit of description. For example, what are the two boards seen in the third and sixth photographs? What are the 3 LED's on the front? Is that a soft start on the inside front of the chassis?
Thank you, Byron! It took me some time to complete this amp, but I really enjoyed it. Specially for reusing some parts, like the computer chassis and processor heatsinks.
Photos 3 and 6 show the fan controller (http://www.diyaudio.com/forums/solid-state/178333-2-speed-fan-controller.html#post2389145) and the power supply connection to ground (http://www.diyaudio.com/forums/powe...roid-transformers-what-right.html#post2088079).
The three LEDs are: green means power on; yellow, "the heat is on", and red, "burning, burning, burning"!!! I will also connect the "reset" button beside the leds in order to provide a "full throttle" for the fan for a few seconds.
The soft start is a small board (with a yellow relay), "floating" in the center of the back panel inside. A really simple circuit with two transistors and a zener diode (http://darrenyates.com.au/electronics/archives/44), powered initially by a secondary power supply (a 12V-wall wart!, that also powers the fan circuit), but maybe I will use a $0.66 step down buck converter from AliExpress, connected to one of the four 38V supplies. Idea from a Texas Instruments application note (http://datasheet.octopart.com/LME49810TB/NOPB-National-Semiconductor-datasheet-5353855.pdf, http://www.ti.com/lit/an/snaa057b/snaa057b.pdf). I chose values so it clicks after 5 seconds.
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