Blown Tantalum Capacitor Advice

shadoooo shadoooo at
Sun Oct 9 12:29:45 CDT 2016

Hello Rob,
I'm quite sure that the tantalum explosion has nothing to do with the
spin-up failure.
Indeed the RD53 (Micropolis) is infamous for a problem in the head
positioning shock absorber.
The head positioning system is based on a voicecoil inserted in the
magnetic field; the angle covered by the head arm is limited by two
adjustable metal limits originally covered with rubber.
At startup the mechanism is moved back and forth to check the two limits,
and exactly at the ends a special magnetic pattern is recorded on the
surface of the disks for calibration.
Due to age, the rubber becomes goo, so the angle limits become wider, so
during the calibration the head falls offer the calibration area and
spin-up fails.
The suggestion is to choose a clean room with few dust and a good lighting,
carefully open the top cover of the disc, and remove the goo the more as
possible using adsorbent sticks.
Be sure not to touch the disc surface with the goo accidentally.
Then try to insert some small pieces of paper over one limit (if I'm not
wrong the failing is the left) in place of the missing rubber, and try the
disc, and continue to add thickness until it works.
Then you are sure about the right limit to move.
Then remove the paper, loosen a little the screw, but just a little so the
limit will not move unless pushed with some strength and a screwdriver.
Then move a very small amount towards the center and try, then repeat trial
and error until the disc starts. Then tight the screw and it is over.
Close the disc and voila.


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