Dewalt random orbit sander: repair runaway speed?

Did someone here address this problem before?
My DeWalt ROS seems to work OK when it's on the wood, but it achieves a frightening speed with no "load". I thought I read that the fix had something to do with replacing a "ring", possibly the "dust seal/brake", but I'm having trouble finding instructions online.
In fact, I've found some discussions online where people seem to think that behavior is normal. That faction advises starting the sander while it's on the wood. My experience is limited, but I don't think that's the way they are supposed to work. If nothing else, you have to remove it from the work at some point; at which time it quickly accelerates unless I "stop" it on a piece of scrap.
I just bought a second unit - a second hand, but evidently unused Porter Cable - that looks essentially identical to the DeWalt except for the color. That one spins slowly when not under load.
So, has anyone here had (and fixed) that problem?
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On 11/02/2015 2:42 PM, Greg Guarino wrote:

I know the P-C intimately and I presume the DeWalt are the same. The "brake" is just an o-ring that goes around the shaft and a dummy solid post--generates a _lot_ of heat so I will, on occasion, remove them on purpose.
But, the fix is trivial; disassemble and find another o-ring of the same size from a local distributor...reassemble.
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On 11/2/2015 6:13 PM, dpb wrote:

from EReplacement Parts) and that did indeed fix the problem. I sucked out a bunch of dust from inside too. Now the sander rotates very slowly when it is removed from the work.
The funny thing is that while looking up this issue online, I found a number of posts from people who were not aware that this was in fact a problem. Several thought that this was normal behavior for a ROS, going as far as to say that you have to start the sander on the work to avoid gouging into the wood when the disk hits it spinning at high speed.
I was pretty sure that wasn't the case, but what convinced me was getting a second sander, one that operates properly.
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On Sun, 22 Nov 2015 11:55:44 -0500

i ran into this problem and cleaning it thoroughly made the problem go away but that was temporary i found out when i used it again recently
will have to get it fixed right this time
it is possibly a dangerous condition as the rpm seems to be a runaway
it is at least bad for the unit and for the project due to the gouging if you do not place it flatly on the surface i think it is a bad design and i wonder if they have fixed it in new models
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On 11/22/2015 1:23 PM, Electric Comet wrote:

Here's the part I replaced:
http://www.ereplacementparts.com/dust-sealbrake-p-69142.html
It was easy to do. Just remove the sanding pad, the dust seal is right behind it.
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