why would someone drop a 909 to the floor while it´s running?
i got no idea either, but recently it happened to a friend. his TR threw a few sparks before the main fuse of his studio blew and gone was the bumm-bumm :(
not to rain on roland´s designing skills (and given the fact usually you don´t throw a 909 on the floor) but the position of the original PSU board is somehow dangerous for flying 909s; since the AC solder pads directly face the bottom plate any impact in that area possibly short-circuits the main AC power. you better put some cardboard or isolating rubber between the PSU board and the bottom plate - well, it´s best not to throw 909s on the floor too ;)
unfortunatelly in our case the the shorted AC line was led to the voiceboard PCB through the metal battery compartment, blasting a few semiconductors and GND traces there. see the picture for details (note the PSU has been exchanged on the image already):
certainly the main transformer was blown after this accident. as the 909 had to be returned into its productivity environment asap (sic!) there was no time to organize a suitable transformer so i had to exchange the PSU completely…
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