Heatsink problem

Clive Arthur · 2018-10-30T17:42:22+00:00

I have some equipment which uses a power amplifier (15 lead TO-220) mounted on one of these on a PCB... No problems until now, it runs cool because the duty cycle is low, in fact it would be fine without a heat sink, I just need the power for a few percent of the time. However, a new customer wants to use the equipment in an unusual manner such that the duty cycle for the amplifier is high, above 50%. Consequently, it gets hot and goes in and out of thermal limit. It's not far off working and takes several minutes or tens of minutes to manifest the problem. I can't spare much extra height, don't want to change the board, fans are ugly. So I'm thinking a right angle of aluminium with a large horizontal surface area and a thick vertical tab for the amplifier. Or copper. Or maybe leaving the heat sink as it is and screwing a large flat plate on top (the heatsink is the highest thing on the PCB). Heat pipe? Just casting around for ideas. Cheers -- Clive

Oct 30, 2018 21 Replies

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Clive Arthur 7 years ago

It's ok, I have some Lego and Blu-tack holding it[1]. Fortunately, making it a bit bigger and Aluminium means it'll fit on pillars to four existing holes.

[1] True.

Cheers

Clive

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Chris 7 years ago

Use a lot of s/hand kit here, routers, firewalls, computers and fans nearly always need replacing, or at least need a service. Old quality test gear like HP always used ball bearing fans and they will last forever if you carefully peel back the label and put couple of drops, (don't drown it:-) of good quality instrument oil, preferably synthetic, low evaporation. Picked up a litre of Aeroshell 12 a few years ago, designed for a/c instrument bearings and that seems pretty good.

As for new fans, don't bother with anything other than ball bearing if you want to fit and forget. Server fans are usually ball bearing, high speed and noisy, though you can downrate them to a slightly lower voltage with using a series resistor. Loads of them on Ebay s/hand...

Chris

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