How long after shutting down a power supply is it safe to open the power supply?

matt020

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As per the subject,

I have an Amiga 2000 and I want to dust out the power supply. How long after shutting down should I wait before the power supply has lost all charge so I can open and get inside?
 

rkauer

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Time varies. As a rule of thumb, wait at least 20 minutes for modern AT-ATX PSU to discharge.

But the A2000 PSU is a different beast, of course. Wait 30 minutes with the power cord disconnected.
 

Harrison

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The large capacitors in PSUs can hold their charge for quite some time. I opened a PSU recently to replace a fan, and that PSU hadn't been used for a few days, but I accidentally touched one of the large capacitors with a screwdriver and it still gave me a real kick. So you still need to be careful regardless of how long you wait.

Not as bad as CRTs though.
 

Templar

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If I were you. I'd left my Amiga turned-off for a day and then start. Not big deal. You will be 100% sure, and of course take out the power cord from the socket.
 

AndyLandy

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Best thing to do is not touch the capacitors at all, if you can help it. Even if the PSU has been off for a few days, why run the risk.

My solution for filthy PSUs is to remove the lid carefully then attack with a can of compressed air, followed by giving it a once-over with a hand-held vacuum cleaner.
 

chiark

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Turning the power switch on when it's unplugged can help drain them. Waiting days sounds a little daft to me.

Best bet is assume they're energised and try hard not to touch them. They can give you a bit of a belt, but I'm still here ;)
 

rkauer

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Some bad assembled PSUs don't have the discharge resistors placed, which is wrong. Sparing £0.04 for the resistors is just wrong.

Amiga PSU (all of them) have the discharge resistors, so half an hour is more than enough to crack open them.
 

Kin Hell

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The large capacitors in PSUs can hold their charge for quite some time. I opened a PSU recently to replace a fan, and that PSU hadn't been used for a few days, but I accidentally touched one of the large capacitors with a screwdriver and it still gave me a real kick. So you still need to be careful regardless of how long you wait.

Not as bad as CRTs though.

Ah! - That explains a lot. :ninja:

:run:

Kin
 

Zetr0

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Firstly I have to admit that I am concerned when some one asks this question.


To be honest, if you dont know you shouldn't do in this case, you can easly hurt or kill yourself. this can be one of those you wont learn by failing problems, as such I advise you NOT to do this.

however, I cannot in good consience let you do this unarmed, so if you are going to do this, please do it this way


To discharge a small capacitor - touch the two lead terminals with the tip of a screwdriver that HAS with insulated handles will do the trick[/B].

However, handling high-voltage capacitors, is a different story. You should attach a test light onto the capacitor's terminals to safely dissipate the stored electrical currents.

Make sure that you completely discharge the capacitor - before you handle the cap, I would suggest that you touch the terminals with the tips of the screwdriver once more.

Alternatively get a light bulb - its handy for the purpose (make sure it can take the voltages that the cap is rated for!. Just simply touch its threaded base onto one of the capacitor's terminals. If it still contains electrical charges, it will light the bulb up. let it run untill the light fades out and then with insulated screwdriver discharge the last bit of juice by touching the leads together with the driver.

BE UBER CAREFULL



Disclaimer -

Notice: I do not accept any responsiblity or liability in this activity of yours. Should that you wish to risk your life and that of your components - this is soley YOUR responsiblity. I would advise you to seek a qualified electrician whom can help you on this matter. I wont take any liability or repsonsability in any use or mis-use of the information above. This is on your OWN ONUS - thats to say its your fault in any event of damage, death or wham regrouping and playing at wembly!
 

rkauer

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In other words: to avoid The Wham! regrouping, leave maintenance of PSU units to experienced technicians.
 

Zetr0

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In other words: to avoid The Wham! regrouping, leave maintenance of PSU units to experienced technicians.


no truer word said my friend.... no truer word said!!!
 

Justin

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unplug, open it up, get wife/partner/offspring to touch PSU if wife/partner/offspring survives continue repair :)
 

Harrison

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Discharging Capacitors... that's what cats are for!

:run:
 
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