Phase Linear 400 Odd Heatsink.

FredR

FredR

Veteran and General Yakker
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WTF?
I got this heatsink back in 2019 off eBay. The guy said it was off a series II, but I've never seen a heatsink like it. All the TO-3s are properly placed but the depth of the 8 fins is not standard. Anybody know where this is from?20210423_234009382_iOS.jpg20210423_233944862_iOS.jpg
 
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Also the heatsink construction is one piece.
 
Hi Fred
I have a couple of these. Much better than the two piece heat sinks and they have more surface area than the equal length one piece heat sinks. I think these are their best ones. The equal length ones have thicker sections so are stronger against bending.
 
grapplesaw said:
Hi Fred
I have a couple of these. Much better than the two piece heat sinks and they have more surface area than the equal length one piece heat sinks. I think these are their best ones. The equal length ones have thicker sections so are stronger against bending.
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From Phase Linear?
 
These are same as mine. Stock from phase linear.
I believe they are better for heat transfer to air
 
I have that cast/extruded one on the 400 S2. I much prefer it as the amp can sit stable and level on the transformer and fins, face plate up. Also, the output transistor mounting area is flatter, better contact for heat transfer.
My 400 S1 has that eight fin extra long one made out of bent plate. The fins are so damn long that I need to put a piece of 2x4 under the transformer bell to stand it face plate up. And there's probably a sizable thermal break between the base and those extra fins. Mine never get hot, maybe just a little warm, if I really crank it. I think those giant S1 fins were pure marketing.
 

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Same here on my 400 II. @George S. I noticed you have the protective cover snapped back on the outputs...is that advisable on the WOPLs? I would assume they don’t help with airflow on the cans or is that irrelevant? I left mine off
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e30m3mon said:
Same here on my 400 II. @George S. I noticed you have the protective cover snapped back on the outputs...is that advisable on the WOPLs? I would assume they don’t help with airflow on the cans or is that irrelevant? I left mine off
View attachment 50310View attachment 50311.View attachment 50310View attachment 50311
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My amps run very cool. But then, they're not rack mounted, they sit in the open on a wood shelve.
Also, they are in a biamp configuration using a MiniDsp 2x4 and the system is calibrated using REW software. Big mains and subs, 2 400 WOPLs, active crossover, and REW make for a very efficient system.
 
e30m3mon said:
is that advisable on the WOPLs?
Click to expand...
If you play with your amplifiers, as opposed to putting them on a shelf and never touching them, then you want the covers on to prevent a shock. There is 170 VDC, more or less, from one column of output transistors to the next in a PL400. Just reach over the top to dust off the amplifier and your dangling nose pickers will find that voltage. Don't ask me how I know this...
I don't believe removing the covers will help with heat dissipation. We are talking about heat "conducted" from the transistor die to the heatsink, which is very efficient in aluminum.
You are thinking of "radiation" or radiant heat through the air from the output transistor case to the covers, very inefficient heat transfer.
In fact, the transistor covers add some additional mass and surface area to conduct heat from the heatsink and into the air.
 
Ok, got it guys. Mark, I actually experienced a slight tingle while poking around back there and that reminded me about the high volts. Thanks.
 
I was home alone yesterday as wife was off taking care of some family business. At approximately 1030 I cued up 52 Ramones albums on Foobar2000 and let them play continuous and LOUD while I did some yard work out back and finished up the Hakko units upstairs. The system was cranked, media room windows were open as it was a warm day in Ohio, working outside the music was loud, upstairs working on the Hakkos the music was loud. The meters were swinging up to 1/4 of travel. Nine hours later after not touching the system I felt the amps for heat.
The fins were slightly above room temp, the output covers were warm, the transformers were warmer, and the top cover plate was the warmest. But nothing was hot.
To improve the cooling, if needed, maybe more holes or slots in the top and bottom plates are required. I can envision a steel mesh with a frame.
Perry recommended a nice fan unit some time ago that sits on top of the amp and blows upward. Rather than more air on the fins, I think cabinet ventilation may work better.
But then, if it's rack mounted, choices are limited.
 
George S. said:
I was home alone yesterday as wife was off taking care of some family business. At approximately 1030 I cued up 52 Ramones albums on Foobar2000 and let them play continuous and LOUD while I did some yard work out back and finished up the Hakko units upstairs. The system was cranked, media room windows were open as it was a warm day in Ohio, working outside the music was loud, upstairs working on the Hakkos the music was loud. The meters were swinging up to 1/4 of travel. Nine hours later after not touching the system I felt the amps for heat.
The fins were slightly above room temp, the output covers were warm, the transformers were warmer, and the top cover plate was the warmest. But nothing was hot.
To improve the cooling, if needed, maybe more holes or slots in the top and bottom plates are required. I can envision a steel mesh with a frame.
Perry recommended a nice fan unit some time ago that sits on top of the amp and blows upward. Rather than more air on the fins, I think cabinet ventilation may work better.
But then, if it's rack mounted, choices are limited.
Click to expand...
I thought about that myself. There’s a lot of air space inside the cabinet and we usually rely on convection to keep things at a safe operating temperature, the 700 has two thermal cutoffs (one in the 400). At what point does heat become critical inside the cabinet? There are heatsinks on critical transistors on the driver board, again, relying on convection.

So far, I haven’t heard anyone on this forum remarking about thermal failure.
 
I'm going to look at the top and bottom plates and consider drilling ventilation holes. Getting those Budwig feet under those amps has to have helped.
I can stack all the plates and drill right through. Probably screw them onto a scrap board, mark holes in pencil in a grid pattern, center punch, drill, de-burr, done. Another project!
 
George S. said:
I'm going to look at the top and bottom plates and consider drilling ventilation holes. Getting those Budwig feet under those amps has to have helped.
I can stack all the plates and drill right through. Probably screw them onto a scrap board, mark holes in pencil in a grid pattern, center punch, drill, de-burr, done. Another project!
Click to expand...
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...
 
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