DEC RD53 hard drives are notorious for failing due to the heads getting stuck. The drive will spin up and then spin back down a little while after it gets up to speed. You won't hear the normal sound of the heads moving to track zero. Information online says this is due to a rubber bumper that gets sticky preventing the heads from moving off it. Others have successfully opened the drive and freed the heads. The consensus is that without removing the bumper the heads will soon stick again. I was not able to find the bumper. So far the heads have not stuck again on my drive but it hasn't been that long. The picture and picture links below show opening the drive and where I pushed to free the heads.
The picture below shows where to push with a non magnetic and non conductive tool after the drive is up to speed to free the heads. More pictures in the links below.
The DEC RD53 are rebadged Micropolis 1325 drives so the same repair should work
on them. Online information says that soldering a jumper at R7 makes the
drive a RD53.
The following picture links also have descriptions of what is shown in the pictures. Thumbnail Picture Selector
Drive in "Clean Room" ( 68K) Drive Air filter ( 59K) Drive open ( 75K)
Actuator view 1 ( 76K) Actuator view 2 ( 62K) Free heads ( 76K) Free heads 2 ( 79K)
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The following picture links also have descriptions of what is shown in the pictures.
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