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Amplifier goo

bsabel

bsabel

Well-Known Member
I'm in the process of recapping my first receiver - a cute little Rotel RX-402 - and ran into something new to me. The transistors are mounted on a U-channel type of heat sink. The heat sink is then attached to the back panel of the receiver. Where the two meet was a goo that is remarkably similar to petroleum jelly.

I can't think this would be any kind of thermal paste but I'm not sure what purpose it would serve. Perhaps the opposite - to insulate the back panel from the heat sink? Anyway, I had to clean it off to work and am wondering what, if anything, I should replace it with.

Here's a pic for you! The red arrows show the surfaces that had the mystery goo.

2012-02-28_21-50-19_886.jpg
 
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It may be some type of conformal coating to stop any electrolysis between the aluminum sink and the steel case. If it was me, I'd replace it with a silicone based thermal paste, it will help heat transfer and provide the same separation between dissimilar metals. I use Thermalcote.
 
I think you will find it was silicone grease - not the same as thermal compound - as you say, more like petroleum jelly.
 
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dielectric grease is the fancy name. Its silicone grease, and indeed, not a particularly good thermal transfer goop. A silicone thermal goop would probably be a better idea. It would stop corrosion, and transfer more heat to the cabinet for better heatsinking.
 
So just slather that whole side with standard thermal compound and I'm golden? Or was there a reason they didn't do that in the first place? I'm wondering if it's a situation where they worried that too much heat would get transferred to the back plate. :dunno:
 
I was more thinking of potential heat damage to the finish of the back plate or some of the components. But, as far as the transistors go, sure, the more heatsink the better.
 
i don't think the Rotel will get hot enough for any of that to be a worry. i'd stick with the thermal paste.
 
Well, it doesn't sound like we have consensus on what it is. But I'm at least sensing there isn't an ohmygoddontdothatyou'llblowupyourhouse risk if I just use regular old thermal grease, right?
 
it might just blow up the whole street:D:D
only joking . my guess it will be just fine .only thing is the case may get slightly warmer .
 
ohmygoddontdothatyou'llblowupyourhouse

ohmygoddontdothatyou'llblowupyourhouse :D

(couldn't resist)
 
bsabel said:
I was more thinking of potential heat damage to the finish of the back plate or some of the components. But, as far as the transistors go, sure, the more heatsink the better.
Click to expand...

bsabel said:
Well, it doesn't sound like we have consensus on what it is. But I'm at least sensing there isn't an ohmygoddontdothatyou'llblowupyourhouse risk if I just use regular old thermal grease, right?
Click to expand...
TIM (Thermal Interface Material) aids in the transfer of heat, it doesn't increase temperature. When you reassemble the receiver and use thermal compound, silicone grease, or nothing at all, the temperature of the backplate would be just about the same after the receiver reaches quiesence and has been operating for a bit. My suggestion would be to put a light coating of thermal compound on the heatsink and forget about it.:yes:
 
I've not seen clear grease, but several manufacturers used regular heat sink grease for bolting heat sinks together. Sansui 9090 and some of the SAE amps come to mind. Use it where I work for big servo amp assemblies.
 
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