Clip-On Heatsinks

[oldphaser]

Whilst do some more searching on the internet concerning the FTC amplifier rule from 1974, I stumbled across a Crown DC-300A with some clip on heat-sinks. It appears that Crown used these for a while in an effort to meet the 1/3rd power pre-conditioning required for 1 hour. (NOTE: The FTC later allowed for a "cumulative" 1 hour of pre-conditioning.)

Anyway, I found some Crown DC-300A clip-on heat-sinks being sold on ebay so I bought them. Hopefully, I can get them to work with a Phase Linear 400.

See attached photos and web link: http://www.canuckaudiomart.com/deta...00a-laboratory-power-amplifier/images/967295/

Ed

 

[laatsch55]

I wonder how effective the heat transfer was...

 

[Gepetto]

Iwonderhoweffectivetheheattransferwas...

Not very good Lee. The thermal interface when you break the solid, one piece metal construction is quite poor. Especially when both are anodized.

 

[laatsch55]

Anodization works both ways then...

 

[8991XJ]

Those were a very short term addition to the DC-300a. I believe with proper compound they would help an amp driven hard to maintain without reaching thermal overload, something I did on my 300a on numerous occasions. Mine did not have these heat sinks or forced air cooling and was in the early black-banded cabinet. These sinks won't fit on an amp in that cabinet but they should work with the Jeln cabinets. That price isn't high considering there could be a lot of other uses for those heatsinks.

This might be an opportunity to use the highest thermal conductivity heatsink grease on the market to get some good transfer.

 

[wattsabundant]

Does the original test spec allow for a temporary mod? If not I find it hard to believe that Crown could take exception to it in this manner. Why have a spec if anybody can test their product to suit their own best interests.

 

[Gibsonian]

Yes, around here we would call that cheating.

I do really wonder how effective they are? If transfer from fin to fin is really bad then they do as much blocking of heat exchange as they do transfer.

 

[orange]

Clip-on heatsink = clip-on tie? Can't tie it yourself or something?

 

[8991XJ]

I see how on a Phase Linear centric forum that the clip on heat sinks used by a major competitor would be considered cheating. But if the amp was delivered with those attached from the factory, and they were, I don't see that as cheating. If someone decides to remove the clips and the sinks then that is on them.

Look at the Sansui 9090DB receiver. It has a heatsink screwed onto the heatsink that holds the transistors and needs to be removed to pull the output transistors. Is the use of the clips vs. the screws the difference between we don't care and cheating?

The heatsinks will suck heat out of the heatsinks on the amp. There will probably be a difference between the outer pair per side which have longer original heatsinks to suck from and the inner pair which are short sections, what 7.5 inches tall by maybe a bit over an inch wide that is in contact with the add-on heatsink.

Whatever it is added metal mass in contact with the original heatsinks and if the finish is good enough on both pieces, a bit of heatsink compound (best heat transfer rate can be used since not an insulated electrical location) then these should work just fine.

As with many big amps the entire unit is the heatsink. Crown faceplates get warm and I had one, a DC-300a, that got to shutoff temp levels when a friend had the system and there was a stray strand of wire connecting the left channel red and black output binding posts. Amp lived like that for a couple weeks, run a while get really hot on the left edge (rack ear and about 1.5 inches in from the rack ear, vertically along the face of the amp) shut off, cool some and turn back on. Simple fix, amp was fine. Scott had no idea.

But these heatsinks. I think they were well bought as I stated and if they can't be used to augment the sinks on his amp they might be good for mounting smaller power resistors to a test load. Lots of things can be done with these.

 

[oldphaser]

I received the Crown DC-300A clip-on heat-sinks yesterday. They are 6-9/16" to 6-5/8" tall. A bit tall for 400 series heat-sinks which are typically 6-3/16" tall. They are however a better fit for 700 series heat-sinks which are approximately 6-5/8" to 6-3/4" (depending on which series 700 you are using).

Ed

 

[nakdoc]

Heatsink surface area and air circulation are the two critical considerations for heat sinks. Mass only takes longer to heat to operating temperature. Addinf these fins to the existing heatsinks greatly increases surface area. One could bolt on various fins to the stock heat sink too. We used to sit the 400 on top of a box fan to up the air flow.....