Hi all
I wish to mount a 20 watt resistor to a small finned heat sink. What kinda glue would be good at this task? Also will this increase the wattage rating any? Its a 1 1/2" x 3"x 1 1/2" aluminium sink
I wish to mount a 20 watt resistor to a small finned heat sink. What kinda glue would be good at this task? Also will this increase the wattage rating any? Its a 1 1/2" x 3"x 1 1/2" aluminium sink
Hi,
I recently made up a couple of 50 watt 5.6Ω dummy loads for testing a class D amplifier. The resistors I used were in an aluminium case with holes for bolting to the heatsink at each end. Two tapped holes for each resistor and a small amount of heatsink compound and the job is done.
Maybe you should look into this type of resistor as they are designed to be bolted down and guarantee a good thermal contact with the heatsink without the use of any adhesives.
I recently made up a couple of 50 watt 5.6Ω dummy loads for testing a class D amplifier. The resistors I used were in an aluminium case with holes for bolting to the heatsink at each end. Two tapped holes for each resistor and a small amount of heatsink compound and the job is done.
Maybe you should look into this type of resistor as they are designed to be bolted down and guarantee a good thermal contact with the heatsink without the use of any adhesives.
Thermally conductive epoxy is the only glue you can use for this, but it's not cheap. You would be much better off using the correct resistor as John said.
Yes, power capability of a resistor is set by the thermal resistance between the current carrying wire and ambient, plus ambient temperature.
Submerse the resistor in a water bath of low temperature, and it handles several times the nominal max rating.
If you attach the resistor to a heatsink, thermal resistance between the ceramic case and ambient will be lowered.
How much lower depends on how it's attached and how much of the outer surface.
e.g. sticking one side of a square cross-section cement wirewound with glue to a heatsink will merely lead to a marginal rise of the max power figure.
Thank you all for the reply's. I think i will try clamping the resistors between two of the heat sinks i have or one heat sink and some 1/4" thick cooper bus bar i have. Would love to have sinked resistors but in this area i live rat shack is my only source of parts without ordering off the net. And they do not carry them.Plus one of my new years resolutions is to get my credit cards balances down. So that means using up my years of hording parts to DIY whatever i need instead of just hoping on-line and going willy nilly.
I saw an unusual approach to this the other day.
Ram the resistor down a copper tube, the tube became a square in the process like a close fitting jacket. Then the copper jacket can be soldered to a copper plate. Maximum area of the resistor being cooled by the high thermal conductivity of copper.
Ram the resistor down a copper tube, the tube became a square in the process like a close fitting jacket. Then the copper jacket can be soldered to a copper plate. Maximum area of the resistor being cooled by the high thermal conductivity of copper.
My mental picture of that involves much damage to the resistor before the copper tube deforms from round to square! 😱
Hi KatieandDad
Thank you for the info i ended up sandwiching the resistor between two of the heat sinks i mentioned in previous post. I think it will be sufficient for the little Sansui AU-4400 I'm attempting to get right. the resistor is 20 watts and the amp is a 20 to 25 watt integrated from 1975. But i may play with it a little i have a old PA amp that will throw a butt load of wattage at it. A old Peavy CS 8000 built like a tank that has seen more mileage than me. 😀. When i get home from Roanoke Va. this weekend might just have to see how much this thingamabob can handle. I like to make smoke happen.The great thing about being a total noob to this hobby is i have no preconceived notions about much of anything. But i love sound and music. Plus my son like to hang out and learn. He is 6 and has a grasp on the math that i didn't learn till i was in Jr, High. But then again he is super scary smart.
Once again thank you for the reply's Sam .
Thank you for the info i ended up sandwiching the resistor between two of the heat sinks i mentioned in previous post. I think it will be sufficient for the little Sansui AU-4400 I'm attempting to get right. the resistor is 20 watts and the amp is a 20 to 25 watt integrated from 1975. But i may play with it a little i have a old PA amp that will throw a butt load of wattage at it. A old Peavy CS 8000 built like a tank that has seen more mileage than me. 😀. When i get home from Roanoke Va. this weekend might just have to see how much this thingamabob can handle. I like to make smoke happen.The great thing about being a total noob to this hobby is i have no preconceived notions about much of anything. But i love sound and music. Plus my son like to hang out and learn. He is 6 and has a grasp on the math that i didn't learn till i was in Jr, High. But then again he is super scary smart.
Once again thank you for the reply's Sam .
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