68kMLA Classic Interface
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| Quadra 650 does not start up - capacitor blown and a bit of mystery | |
| Posted by: bobo68 on 2015-07-05 04:06:31 Hi, I acquired a Quadra 650 which was in very good visual condition but would not start up. I'll make the long story short: the Quadra has a blown capacitor C203 on the underside of its mainboard:  (the cap was initially "complete" but blown - one part fell of when I tried to clean the surrounding) The "explosion" left some smoke on the housing:  Somebody put some clear tape across that part of the mainboard (obviously after the explosion):  The mainboard PRAM battery (which of course I thought was the reason for the Quadra not starting up) was probably installed the wrong way (polarity). I ripped the old one out quickly without checking but I think it was reversed. The battery is from 1997 and still has 3,6 V - another indication that it was installed wrongly because it should have been empty by now. The PSU is working, I can start it up by shorting output pin Pin 9 (/PFW, power fail warning) and pin 10 (+5V.TRKL). It obviously cannot be started up by the Quadra. There is a thin film of some sticky (dried up?) stuff on the underside of the mainboard. I thought that maybe somebody poured Coke etc. into the Quadra and the mainboard got a little bath but the inside of the lower housing is clean. The upper side of the mainboard is also pretty clean. So:
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| Posted by: Floofies on 2015-07-12 11:42:08 After a quick trip to Trash80's Cap Replacement Guides, it doesn't look like there's a guide for the Q650 yet. Set your multimeter to Continuity mode and trace the circuit between the battery contactors and the C203 pinholes. You might have to try a few configurations before your multimeter picks up anything. The mode icon usually looks like this on most multimeters. This will tell us (within a margin of error) whether or not it may have been the battery that caused the cap to fail. As far as I know those little ceramic caps do not usually explode on their own, so it's likely it was the battery. | |
| Posted by: tanuki65 on 2015-07-12 16:44:01 Send the motherboard to Uniserver/Charles Phillips. He got my IIci's sound working (though my RAM was still bad). | |
| Posted by: 360alaska on 2015-07-12 20:16:10 It should be noted that q650/700/800's don't suffer capacitor leakage because they already have tantalum caps, that being said if you can't figure out what's going on: http://www.ebay.com/itm/APPLE-661-1676-820-0380-04-QUADRA-800-WOMBAT-SYSTEM-BOARD-WITH-CPU-W-WARRANTY-/141592585530?pt=LH_DefaultDomain_0&hash=item20f793653a The Q800 and Q650 have the same board... I have a spare Q700 board and that would also fit if it might help you... | |
| Posted by: uniserver on 2015-07-13 00:38:46 http://www.ebay.com/itm/APPLE-Macintosh-CENTRIS-650-Working-Computer-w-Original-System-Disks-/201381252636?pt=LH_DefaultDomain_0&hash=item2ee3420e1c I suggested this one to him a while ago. i wonder if he bought it? went for a good price. | |
| Posted by: bobo68 on 2015-07-13 12:22:56 I ordered a replacement cap. Will feed back after I installed it. | |
Posted by: 360alaska on 2015-07-13 12:42:39http://www.ebay.com/itm/APPLE-Macintosh-CENTRIS-650-Working-Computer-w-Original-System-Disks-/201381252636?pt=LH_DefaultDomain_0&hash=item2ee3420e1cI just bought a logic board for my Q700 🙂 It identifies as a Q650 and not a Q800 though.. | |
| Posted by: uniserver on 2015-07-13 12:45:49 well a q650 in a q700 case is the cats meow. 😀 bobo68, ok cool... i hope it works our for you... i feel like its wishful thinking, but ya never, know i hope it works! | |
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