Phase Linear 400 Odd Heatsink.

George S.

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#21
Please don't drill your amplifier, you will just ruin the covers. If you want more airflow, you have to force it through the openings, get a fan! The engineers at PL determined the exact size of the openings to allow natural convection of air based on the temperature differential and the cubic size of the chassis interior.
Or, send me the covers and leave your top and bottom open...
No fans for me. Really not concerned about keeping the covers stock as little of the amp is unmodified. Drilling can be tastefully and logically done. Or new covers fabbed. The original venting could be improved.
 

George S.

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#23
How large a hole saw should I use? Can't remember if the bottom plates even have vents. Have to look this coming weekend
 

George S.

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#25
Good deal. Probably use same size bit as vent width, extend them, add another row or two or three. Keep same spacing so it's pleasing to the eye. Lay it out on the drafting board, cut it out and glue on with rubber cement. Center punch, drill thru all 4 plates at once, remove the paper, rub off the rubber cement, de-burr with a countersink bit.
Then again, I really don't need to do this, but may pay off in the long run. Be interesting to see if it makes a difference.
And then again, it's a bunch of work. Probably better off doing something else with my time.
 
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mlucitt

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#26
Center punch, drill thru all 4 plates at once, remove the paper, rub off the rubber cement, de-burr with a countersink bit.
There are PL purists all over the world cringing at this thought process. Plus, Joe basically saying, "Don't drill your covers."
I will buy your unmolested original covers for $20.00, then you can fabricate some new covers and go crazy with your drill, hole drill, roto-zip, Sawzall, or whatever you wish.
 

George S.

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#27
There are PL purists all over the world cringing at this thought process. Plus, Joe basically saying, "Don't drill your covers."
I will buy your unmolested original covers for $20.00, then you can fabricate some new covers and go crazy with your drill, hole drill, roto-zip, Sawzall, or whatever you wish.
I might fab some new covers just to see if there is a difference. Really thinking about 3/8" holes in a tight grid. There's a metal supplier near me that will cut to my specs and very reasonable cost. If I do it I want to do it right, really don't want to drill around the vents. The design wouldn't be "pure". So we'll see if it happens. I won't drill those original covers. You raise a valid point, however I did drill the bottom covers for feet.
 

mlucitt

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#30
I've even drilled holes in the faceplate.
The horror...
Actually, we are interested in hearing about your results. Keep in mind that electronics are happy at temperatures between 100F-150F. This reduces moisture and makes the electrons move faster. The components are not like humans, we like 68F-72F.
 

Gepetto

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#31
The horror...
Actually, we are interested in hearing about your results. Keep in mind that electronics are happy at temperatures between 100F-150F. This reduces moisture and makes the electrons move faster. The components are not like humans, we like 68F-72F.
And keeps the ever important bias transistor servo working properly. Bias transistor too cool compared to the heatsinks spells disaster...
 

George S.

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#32
I think covers need to be installed to help preserve the structural integrity of the chassis. It's pretty damn thin and flimsy, luckily mine don't appear to have ever been rack mounted, that's good.
Even with the covers off, I tend to think there's enough inherent heat to support the bias transistors working properly, or am I wrong?
Been wanting to try some home anodizing for some time. Thinking fabricating some drilled covers might be a good reason to pursue anodizing.
At the end of the day, my 400s don't have any issue with heat, but, if drilled covers would better vent the chassis, then why not pursue that.
 

George S.

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#33
Whoa, whoa, whoa, stop right there. Just dawned on me Joe most likely has the WOA parts calibrated to work with the factory venting. Am I right or wrong?
 

Gepetto

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#34
Whoa, whoa, whoa, stop right there. Just dawned on me Joe most likely has the WOA parts calibrated to work with the factory venting. Am I right or wrong?
As did Phase Linear...too much bias is a very dangerous thing when the amp warms up. As the amp heats up, the bias voltage moves down because the B-E forward voltage of the driver and output stages likewise go down as they heat up. If you cool the bias transistor on an operating amp with the hot heatsinks, you are headed for cross conduction
 

George S.

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#35
Ahh, I see. Good to know. Mark, thanks for saving 4 plates from the drill. Going to study this and understand it. Thanks Joe.
 

Gepetto

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#36
Maybe I am too subtle... :) Will be more assertive the next time :)

The control board electronics are truly loafing in there, huge overkill...
 

George S.

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#37
Joe, "bias servo", thought you were joking, as I thought Mark was when said he said those vents were designed by a engineer. Thought servo's were mechanical assemblies, and the designers liked the grills of their new 69 Camaros so they kind of copied them for the vents. Ya got to be more direct! Thanks.
 

mlucitt

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#38
Whew, crisis averted. George, a proper servo has a transmitter and a receiver. Think of when a Naval gun points out over the Starboard side, the little servo receiver on the bridge spins a dial that points to 90 degrees relative.
So it is with the PL amps, Q6 is the transmitter of a voltage signal change due to heat generated from the bottom of the heat sinks (near the drivers). The receivers are the driver and the output transistor bias voltages that respond to the signals sent by the transmitter (Q6).
 
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