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olliec420

I just got my grail, Quadra 950. Need advice for restoration.

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Hi Guys,

 

Im new to the forum (and restoring vintage tech) but pretty active in r/vinatgeapple.  Last week a gentleman who cleans out warehouses in search of old tech posted on r/vintageapple and had a 950 in his haul.  (see album here https://imgur.com/a/ypS1VTJ). I made him an offer and he shipped it to me straight up...

 

The outside is nasty but the board is quite clean.  So I attempted an initial power up of the 950 just now. I connected power and pushed the power key on the keyboard (hard drive unplugged form data but hard drive power was connected. The fans raved and the system chimed. Immediately followed by some pops and flashes emitted from the circled area. I immediately pulled the power and since then the office has smelled of electrical fire (I believe its ozone, not sure if that the right term though). Whats my next move? Could it just have been dust burning off? Caps busting? Remove the PSU and open it?

 

Any help is appreciated.  Im very excited to get this baby going.  Thanks!

 

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Well I see mold and wetness so it could be something was wet inside the unit and shorted out. It could also be a power supply cap blowing up from age.

 

Generally when I get something that looks like what you have I take it apart and clean it while looking for issues before i power it up.

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43 minutes ago, Unknown_K said:

Well I see mold and wetness so it could be something was wet inside the unit and shorted out. It could also be a power supply cap blowing up from age.

 

Generally when I get something that looks like what you have I take it apart and clean it while looking for issues before i power it up.

Well... I dont know if that would have helped in this case, I definitely didn't detect and moisture and its been in climate control for 72 hours but yes you're right...  I was more worried about the PSU being bad and putting out voltages that could damage the board, that may be what happened.   I disassembled and found the culprit...

Please tell me this can be fixed.  I think I can solider a new one in place if I can get the right part.  I just hope nothing else was damaged in this process. 

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Looks like it is a tantalum capacitor that is associated with that three terminal 7805 5V regulator next to the failed cap. From the marking on the cap it is a 10 uF 6V part. I'd replace it with a 10V or 15V part if you can find one to give a safety margin.

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Replacing it should not be an issue. I would check the 5V regulator next to it to see if it is shorted (causing the capacitor to over voltage and fry). If it is fine the capacitor could just have died on its own and the machine might even work without it.,

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16 hours ago, Unknown_K said:

Replacing it should not be an issue. I would check the 5V regulator next to it to see if it is shorted (causing the capacitor to over voltage and fry). If it is fine the capacitor could just have died on its own and the machine might even work without it.,

Hi, thanks for the info and help.  Would you instruct me (or point me to instructions) on how to check that regulator?  From what I read in a thread by BadGoldEagle, it could be the PSU going bad putting out bad power.  In which case I wouldn't want to reconnect it and attempt any thing more until I know the PSU is good.  There is a pricey one on eBay but then again I dont know if its good either.  They seem to be known to fail.  

 

Also I'm quite excited about this computer.  During my middle school years I had a 040 and I literally never had one problem with the hardware so I dont have much experience with them.  I may have a lot of questions.  I have several beige PPC machines working at home but no 0x0's and I want to get this baby all fixed up right.  I know a lot about standard PC parts as Ive done IT for 20 years but that doesn't do me much good here.

 

In your other reply you said you take them apart and clean them.  My board looks pretty good but there some spider webs at the bottom and a little bit of dust.  What is the best way to clean this board?  Battery is removed and there is that one burnt component.  Just a dusting with compressed air and soft cloth or alcohol/water?  etc.  I have several power Macs at home that are in real need of cleaning and the info would be helpful.  Thanks.

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Not much to those 5V regulators:

 

https://www.instructables.com/id/7805-Regulator-5V-Module-Easy-Tutorial/

 

There are 3 legs, input, ground, and output. Check the input and output with a multimeter to see if they are shorted (under 1 ohm).

 

If you look at that top picture of the link you will see there are capacitors on the input and output side to smooth out the voltage (the input side is the one that blew up on your board). For the device to work you need an input voltage 2VDC+ over the output which is 5VDC. 

 

Tantalum capacitors are very explosive if you go over their rated voltage for even an instant or if you put too much current through them (thermal runaway). Since that part just looks like it over heated you probably had a short somewhere on the board.

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27 minutes ago, Unknown_K said:

Not much to those 5V regulators:

 

https://www.instructables.com/id/7805-Regulator-5V-Module-Easy-Tutorial/

 

There are 3 legs, input, ground, and output. Check the input and output with a multimeter to see if they are shorted (under 1 ohm).

 

If you look at that top picture of the link you will see there are capacitors on the input and output side to smooth out the voltage (the input side is the one that blew up on your board). For the device to work you need an input voltage 2VDC+ over the output which is 5VDC. 

 

Tantalum capacitors are very explosive if you go over their rated voltage for even an instant or if you put too much current through them (thermal runaway). Since that part just looks like it over heated you probably had a short somewhere on the board.

Very helpful.  Thanks a bunch.  I will get to work on it this weekend hopefully.

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You will probably have to remove the regulator from the board to test it, otherwise you may see the effects of other capacitors between either the input rail or output rail and ground giving you an impression that there may be a short. The exploded capacitor on the input rail pin is there to provide some stability for the voltage regulation, but there may be enough additional capacitance on that voltage source that it could just be removed and it would still work ok as Unknown_K stated.

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FYI, you can test the PSU on its own by shorting the blue (5V stb) and the white (Power ON, PFW) wires together. Unplug it from the Quadra first of course...

I'd use a surge protector and/or a power strip with a switch to prevent any further damage. If it doesn't explode, you can test the voltages with a multimeter. 

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On 2/14/2020 at 6:51 PM, cruff said:

You will probably have to remove the regulator from the board to test it, otherwise you may see the effects of other capacitors between either the input rail or output rail and ground giving you an impression that there may be a short. The exploded capacitor on the input rail pin is there to provide some stability for the voltage regulation, but there may be enough additional capacitance on that voltage source that it could just be removed and it would still work ok as Unknown_K stated.

 

Oh I see.  I dont want to remove anything I dont absolutely have to.  I understand this stuff at a novice level and have dont simple solder jobs (poorly I might add) and I really dont want to damage this thing any further.  Today I spent time reading and digesting Trag's post on the SMC capacitors he has for sale and soldering tips.  I feel like I can safely remove the burnt capacitor.  I may be confident enough to replace it as well but I'm going to have to practice on some old worthless boards laying around.  I dont know if I should go that route or find someone to do the job properly and pay them.  

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