Show us yer heatsinks!!

[Mark Hammer]

The subject of heatsinking small power-amp chips came up in the "Fried 386" thread below.  While there is an abundance of heatsinks availabe for power transistors, and even some for "can-style" IC's, there isn't very much for DIP style IC's.  In most instances one has to invent something on the spot.

If you have come up with some sort of impromptu heat sink that might be usable for any of the little power amp chips like 386, LM380/384/1877, NJM2073, TA2025, etc., I think we'd love to either see it, or have some sort of blow by blow description of what you did and how.

Hep the rest of us stop smoking (well, our amps actually) and SHOW US YER HEATSINKS!

[bwanasonic]

I just bought this little kit for the fan, but the included sinks might be of some possible use for this application:

http://www.mikhailtech.com/articles/cooling/vantecbundle/

The small sink is just over 1" X 1". Not sure what it ould be like to try and cut it into smaller sections, or how you would fasten it to a 386, but...

Kerry M

[niftydog]

can't really help with the DIY variety, excpet to say make sure you use a thermally conductive, heat resistant glue. //www.loctite.com is a good place to start. I guess with a decent glue, you could use just about anything.

I've salvaged a bunch of these from old gear at work. Very handy!

[petemoore]

I 'd Epoxy next tiem
 Last time I used super glue.
 Just took a piece of copper sheet about 2'' by 2'', and cut corners out so it'd fit a 386, sort of a 'square butterfly looking piece.
 Then just drilled two holes on either side of where the OA goes

and soldered one end of a wire to it.
 Solid core, and then put/glued the OA between the sheet and the wire, threading wire through second hole. Actually second hole is away from the OA a bit, so after threading and bending over the edge of sheet in the hole to hold tension, I could tighten it by bending slightly more the copper sheet...which now has it's 'wing's standing up, so it'd fit between the electros and other parts that were beside the OA socket on the board.
 Made the 386 that was overheating [it didn't because I kept touching/monitoring it's heat dissipation / ...or buildup] at 'medium speed' didn't get more than slightly warm, and volume was allowed to be increased a good bit [manually] after heatsink was attached.
 It was really quite easy and did the job for the amp [Ruby with discrete Jfet IIRC].
 Something could probably have been done that used for that application aluminum foil actually. Aluminum is quite conductive of heat, the surface area and conduction qualities make it a good candidate for heatsink.
 For something that need alot of heat dissipation for a short period, then has time to recover coolness, then something with greater thermal mass used as heat sink may be preferrable.
 I think for these little amps, something with large surface area, adequate ventilation to surfaces, and great thermal conduction qualities are the main requirements.

[Paul Perry (Frostwave)]

If the leads of a DIP chip are soldered to large thick copper pads, it helps.
Some power amp DIP chips are designed this way.
I would also think about running a copper slab under the chip & out at the ends, as well as the obvious thing of a dissipator on top of the chip. You might want to polish the top of the chip for better contact, use heatsink compound etc. But usually, if you have to heatsink a DIP chip, you are using the WRONG chip :x

[Nasse]

There was long and detailed article about how to improve heatsinking LM380/386 and brothers and sisters in National Semiconductor Audio Handbook. That method of soldering the chip on to pcb with big enough copper area was mentioned, if I remember there was suggestion about the required copper area. No sockets then please. I believe external heatsinks might not help wonders but some limit not much better than without cooling, they just don´t cool the chip as quickly as is needed, when you really really punish it.

How about water cooling, or if you could sub the tuned lm386 in oil bath...

Maybe you could file or sand the case top little thinner and with heat conducting paste...

I have only little practical experience, I stopped my research of the subject 20 years ago. I designed a very nice pcb pattern for LM380 WITH those cooling copper areas and without sockets (wanted more robust thing after blasting my one watt chip amp (it was not lm386 but quite similar Philips TAA300 chip in a round can). I tried to avoid ground loops and spend hours and days designing and checking that pcb. Unfortunately I got no sound off the amp, so there was some silly mistake or something. I did never after that touch National 38x chips, for many years.

EDIT There was warnings about heat damage with TAA300 chip, so I knew what I was doing. The pcb was on top my 8 ohm wired 2x12 cabinet with huge magnet powerful guitar speakers, and I was touching the chip with my finger every now and then so I have an idea how the temperature was when I killed the chip. I played too loud too long time, so the chip temperature was near max, and some transient gave the last nail to it´s coffin. If there would have been a temperature display responding fast enough, showing the chip average temperature AND fast temperature rise, that would have been cool thing, I could have stayed near the edge without falling down to total silence and darkness. Such a display on a 386 amp would be cool, though not as cool as Nanohead but anyway, just daydreaming.

[Johan]

it helps if you solder in these chips and also dont cut the legs. sockets are good for testing ICs in tubescreamers but they dont transpose the heat away from the ship ( and in swedish climate they corode, wich is why I dont like them..) but the extra mass of the solder, legs and the cupper surface helps the ship keep coolder ( or should I say less hot..)
...but you can allways superglue a coin on top if the IC if there is room around it...

Johan

[Paul Perry (Frostwave)]

It is possible to get (at emormous expense) paint that changes color with temperature. Some is reversable, some isn't (the latter is used to show if aircraft parts have been overheated & might have lost strength). Might be useful for serious heatsinkers :wink:

[moritz]

It is possible to get (at emormous expense) paint that changes color with temperature. Some is reversable, some isn't (the latter is used to show if aircraft parts have been overheated & might have lost strength). Might be useful for serious heatsinkers :wink:

you mean like those neat little toys cars i used to play with as a kid... the ones that go one colour when you put 'em in the freezer, and then change to another colour when you run them under warm water? Boy, those were the days...  

[RDV]

I've had no problems with my 386 based amps getting overheated, but my LM3886 amp is another story. I used a terribly undersized heatsink for it, but solved the problem by using a salvaged 12v fan(suspended in front of said heatsink) from a CPU. I tapped off my bipolar supply for the preamp with a 317 set for 12v, and viola! Cool heat sink(and chip).

RDV

[petemoore]

Addendum coolers...
 when installing the chip, run as thick a solid core wire 'with' each IC pin, through the board, coming out bottom and top for extra cooling through the pins. Drill the board holes to accomodate the wires and IC pins, install the IC with these 'cooler' wires coming off the top and bottom of each pin, then splay them out. You may need to 'public domain' surrounding parts like you would houses around an expanding airport, to make room for the 'splays' because the pin coolers would then be splayed  out from all the OA pins.
 This method would give very good transient heat pulse protection I'd bet. But for true H.S.-ers, adding copper sheets to these wires would keep the bugs even cooler.
 lol...if you got a loose solder joint though, your bug [and it's 16 wings] might up and fly away !!!
 I read about old radio station tubes, water cooled, the tubes heads down to near the bases were dipped in a cooling bath, great conduction, stays clean, fantastic transfer of thermal mass. Chips are kinda funny shape to be trying this, keeping the legs out of the water 'n such.
 Ok...for really wakki iddea...spray cooler. Releases cool gas when heat rises.
 I read studies on motorcycle engine fins. Keeping the fins VERY clean increases their 'coolingness' greatly, or alternatively stated, the 'first' layer [ a very thin layer of oil or dust] of Anything on the fins greatly reduces cooling capability.

[Hal]

don't forget the box!  This the easiest and cheepest way to do it, and often most effective.  On my power supply (sorry, no pics) I connected the regulator to the bottom plate.  I used a socket so I dont need to solder it into the circuit.  The regulator is screwed to the bottom plate, with one of those silicon things in the middle of it.