Unusual and VERY annoying whine from an old Mac.

tokyoracer

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Hoping someone could shed some light on this, it's very hard to explain and no recording devices can pick the sound up since the frequency is too high but here goes anyway...

As soon as I plug the power cord into my Macintosh Quadra 630 (bare in mind this is before actually powering it on) I get this really annoying sound from it. It changes too (usually goes higher pitch) sometimes it's un-audiable to human ears but is rare not to hear it when plugged in.
When you unplug it, it sounds like a retr0 hard drive is spinning down for a second.

Could this be a PSU issue? I had a Performa 630 with no issues but sadly sold off it's PSU if that is the problem. :sigh:

P.s. I know its not the hard drive or case fan just to make clear.
 
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Merlin

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tokyoracer said:
Unusual and VERY annoying wine from an old Mac.

Chateau Luis san Wogga-Wogga, perhaps......red, white or rose?? **

** "This is not a wine for drinking; it's a wine for lying down and avoiding.."

:LOL:

Seriously, I'd be looking for leaking caps in the PSU.
 

tokyoracer

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tokyoracer said:
Unusual and VERY annoying wine from an old Mac.

Chateau Luis san Wogga-Wogga, perhaps......red, white or rose?? **

** "This is not a wine for drinking; it's a wine for lying down and avoiding.."

:LOL:

Seriously, I'd be looking for leaking caps in the PSU.
Very good Merlin. :roll:

Getting to anything other then the mobo, cd and floppy drives is a right b******d, would be nice to see a tutorial online for taking apart 630 form factor cases. However I suspect like you say, it's a PSU problem.
 

Merlin

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Sorry Tokyo; the word you were looking for is whine actually...

If the noise starts as soon as you plug it is, then I'd be going for the smoothing caps on the DC side of the mains transformer. You normally get an arrangement like Mains -> Transformer -> Bridge -> Capacitors, then a series of regulators for the various voltages. My guess is the problem is around the bridge to the regulators, as the PSU will be powered on but won't deliver the power to the board until switch on.

Is the PSU ATX-style in the Quadra 630?
 
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tokyoracer

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Sorry Tokyo; the word you were looking for is whine actually...

If the noise starts as soon as you plug it is, then I'd be going for the smoothing caps on the DC side of the mains transformer. You normally get an arrangement like Mains -> Transformer -> Bridge -> Capacitors, then a series of regulators for the various voltages. My guess is the problem is around the bridge to the regulators, as the PSU will be powered on but won't deliver the power to the board until switch on.

Is the PSU ATX-style in the Quadra 630?

Oh yes, good point lol, well I am rather tired I have to say and had in mind a stiff drink.
Ahem, anyway excuses aside, that sounds pretty bang on I'll have to get looking to get access to the PSU, I have taken one out before but not without mangling the case to bits. Doing it properly won't be easy but I'll see how far I get and clear some space.
 
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Hell_Labs

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Could be capacitors? My iMac G3 did it before I put it in the cuboard, and that's what I heard did it.
 

tokyoracer

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Well I managed it after some thinking. Took some pictures of the PSU but will have to wait until tomorrow to upload.

I can't see much wrong with it physically but since my camera can light the thing up like a battlefield maybe that can trace the issue.
 

Merlin

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I look forward to seeing them. You are looking for any caps with bulging tops that might indicate something has happened to it, or any obvious physical damage to the board around them.
 

TheCorfiot

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This is a common problem found on older CRT TV's as they get older.

Because of the varying frequency or pitch of the whine then we are talking about a switching or switch mode power supply arrangement here...
The whine is caused by the windings on the Chopper transformer that are oscillating in sympathy with the frequency that the circuit is operating the chopper transistor at. With age they get a bit loose and the only real cure is to replace the transformer with a new one, unlikely in this day & age unfortunately.

These transformers are much smaller than those found in conventional stepdown & bridge rectification style PSU's - Hence why there are lightweight & heavy A500 PSU's.
I have known someone who has removed an offending transformer and dipped it in hot parrafin wax, allowed the wax to permeate the windings and hence reduced the whine, not tried it myself though.

Still worth checking the Caps though as inefficient caps will produce a more rippled output which will also affect the regulated feedback & cause subtle variations in the switching frequency.

TC :cool:
 

Merlin

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@ TC

I would have gone for an epoxy glue (e.g. Araldite) diluted in a solvent like Kerosene (Barbecue lighter fluid) to permeate the windings, rather than paraffin wax.

At the temperatures the transformer runs at, the wax may melt and bad things may happen. :wooha:

Using a solvent-based epoxy mixture works better as the solvent will evaporate off, leaving the epoxy which is a thermoset material, won't melt and actually is the exact same material used on the windings when they were manufactured.

As a Shell rep, I used to visit a customer called M&I Materials who made the epoxies for coating electrical windings, that's how I know how it's done.

Science is brilliant, innit? (y)
 

TheCorfiot

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Merly

I can't fault that, straight from the experts mouth (y)
Brilliant solution indeedy
TC :cool:
 

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Yes, insulation varnish is the cure you are after. You only need one that don't require to put the transformer into a oven.

Merlin can help with a proper varnish.

Oh, and change the main capacitor (one or two, very near the mains wires) to see if it cures the problem.
 

Tomse

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have you looked at the harddrive ?

they start to whine when they get older, specially some models like seagate and rkauer

(sorry mate, couldn't help myself :p)
 

tokyoracer

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have you looked at the harddrive ?

they start to whine when they get older, specially some models like seagate and rkauer

(sorry mate, couldn't help myself :p)
Yeah I'm certain it isn't that causing it. I'll upload pictures hopefully tomorrow.
 

tokyoracer

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Sorry for the double post and the lateness of the upload but heres a couple of piccy's of the PSU:

IMG_3677.jpg


IMG_3680.jpg


Can anyone tell anything from them?
 

Witcher1979

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Ah my bad, I saw the title "Unusual and VERY annoying whine" and wondered if you guys knew my wife?

But then I saw the mac part when clicking on link. (y)
 
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