68kMLA Classic Interface

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20 SC Psu

Posted by: bibilit on 2016-10-06 08:42:39 I have been handed a 20 SC to have a look at, the PSU is acting strangely delivering the right voltages but unable to spin the hard drive (the hard drive is spinning only when the psu is switched off, for a couple of seconds...) When another PSU is hooked to the HD, this spins and works. When tested withoud load, the voltages of the power supply are a bit above normal, and not sure a 100 % but yesterday think get electrically shocked when touched the inner frame. So all in all, the PSU seems to be faulty. Any idea ?

Posted by: Elfen on 2016-10-06 09:56:17 Caps and regulators are shot - that's my guess.

Posted by: unity on 2016-10-06 10:08:38 ^ My guess also. They can pass the voltage but not the amperage needed.

Posted by: Ferrix97 on 2016-10-06 11:28:40 The PSU should be a Sony unit, most of them have bad output capacitors

Posted by: bibilit on 2016-10-06 23:45:08 Yes Sony unit, and yes probably Amperage issue, but why the HD is only spinning when switched OFF ?

Posted by: Ferrix97 on 2016-10-06 23:47:46 When you turn it off you probably disable the protection circuits, but I'm not so sure about that. Is the HD connected to the SCSI interface? maybe it only turns on when enabled by the mac.

Posted by: bibilit on 2016-10-07 01:51:10 Yes connected to the SCSI interface, connecting another PSU spinned the HD.

Posted by: bibilit on 2016-10-08 10:49:55 Solved. Ferrix was right,mainly two capacitors where shot, getting outputs was confusing. back to work  🙂

Posted by: techknight on 2016-10-09 08:41:24 If two are bad, that means they all are. or close to...

Posted by: bibilit on 2016-10-09 10:21:15 Yes all were replaced...

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