> -----Original Message----- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of shadoooo > Sent: 09 October 2016 18:30 > To: cctalk <cctalk@classiccmp.org> > Subject: RE: Blown Tantalum Capacitor Advice > > 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.
Thanks Andrea. I have done this with other RD53s, but not gone as far as loosening the screws. Unfortunately I have failed so far with this particular disk and will try again another day. I suspect though that in this case the goo has spread more widely in the mechanism and gummed it up elsewhere, making the whole thing a bit sticky. I'd like to find a way to clean it more thoroughly. Regards Rob
