[pcyeh]

I am currently building Mr. Millet's hybrid amp. There are two buf634 on the board. In Mr. Millet's design, he uses heatsink with each buf634. Since I never install a heatsink before, I have some question. The hole on the heatsink is exactly alligned with the hole on the buf634. Therefore I assume that there might be some screw required to connect the two so that the heat can be transmitted to the heatsink directly through the screw rather than the air. I don't know if my guess is correct or not? If I am right, where should I get this screw? It didn't come with the buf634 nor with the heatsink. Should I just pick any screw from the hardeware store that fit the hole size? Or should I get some special one from the electronic supply stores? Can I get it from Radio Shack? Thank you very much for your help!!

 

[zbuddah]

Yep you have to buy a screw for the buf634 and the heatsink. I think they use a 4-40 screw. My radio shack didn't carry any of these screws (I don't think they carry em period), but you can find these at your local hardware shop, I found mine at orchard supply, pretty cheap too like 50 cents for 10 screws.

when you install them make sure you put some heatisnk compound between them to improve the heat transfer.

good luck pcyeh

 

[Possum]

Radio Shack does sell a TO-220 mounting kit for mounting heatsinks to TO-220 package chips (which the BUF634 can come in). The mounting kit includes a 4-40 screw, washer, nut, insulating-type washer (to keep the screw from electrically contacting the metal part of the TO-220 chip), and a mica insulator (to keep the metal back of the TO-220 chip from electrically contacting the heatsink).

The mounting kit is about $1.99 I think.

If you're sure that electrical contact between the tab of the TO-220 chip with the heatsink is safe for your layout and setup, then it'd be much cheaper to buy the 4-40 screw with corresponding washer and nut from a hardware store and just forget about the screw and heatsink insulators.

 

[pcyeh]

Thanks a lot guys!! I will go get some #4-40 screws from the hardware store right away. By the way, what is heatsink compound?

 

[blip]

Heat sink compound is a compound that transfers heat extremely well. The theory essentially is that the compound fills the grooves, scratches and other microscopic or larger faults on the heatsink and chip with a substance that transfers heat at a high rate. This increases the overall heat transfer because more surface area is touching the chip.

I don't know whether or not you need to use any in your case. Where it is most often (read always) used is on CPU heatsinks because they are so influenced by temperature. (Besides that their operating tempt is pretty high and no matter how many fans you have in your case, the air flow is restricted)

I picked up a tube of articsilver 3 (about the best compound on the consumer market) a while back so I use that. If I were you I'd pick up a tube and use a dab of it, why not?

OT: Thinking about the connection between computer ICs and audio ICs, does anyone do watercooling on their amps? Now that would be truly hardcore. (Or as I should say for those of you that get it [h]ardcore.)

 

[Possum]

I believe Grey Rollins of diyaudio.com (GRollins I think) built a water-cooled Pass power amp. There was at least one other member there who had pictures of a water-cooling setup he was working on for an amp.

 

[Dreamslacker]

Quote:

Originally posted by blip Heat sink compound is a compound that transfers heat extremely well. The theory essentially is that the compound fills the grooves, scratches and other microscopic or larger faults on the heatsink and chip with a substance that transfers heat at a high rate. This increases the overall heat transfer because more surface area is touching the chip.

Actually, thermal compound isn't a very good heat transfer material. It's just simply much better than air. Pure metal to metal contact is still better. However, there is minimal surface contact on bare metals due to the many microscopic gaps..
A little hardcore and we'll be mounting heatsinks with Artic Silver 3 or Nanotherm EXP. hehee...

 

[eric343]

Kevin Gilmore does watercooling on his KGIWCPA (Kevin Gilmore Insane WaterCooled Power Amp)... he posted a pic of the ~164 TO-3 transistors mounted to the big heatsink/waterblock awhile ago... it's CRAZY

 

[puppyslugg]

pcyeh:

Don't overtighten the 4-40 screw. You don't want to lower part of the opa634's to 'lift up'.

 

[blip]

Quote:

Originally posted by Dreamslacker Actually, thermal compound isn't a very good heat transfer material. It's just simply much better than air. Pure metal to metal contact is still better. However, there is minimal surface contact on bare metals due to the many microscopic gaps.. A little hardcore and we'll be mounting heatsinks with Artic Silver 3 or Nanotherm EXP. hehee...

True. That's why laping heatsinks is such a good idea.

 

[rickcr42]

BTW-please post a review of the final amp