Apple G4 AcBel API1PC36 PSU has a bad cap?

[stj]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

did you put it in the right way, and where did you buy it - not ebay i hope!

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

Yea, striped leg on the negative side. I even marked the striped side with a black marker pen on the underside of the pcb too before I took the old cap out but after I did Remove it I could see it's marked + and - on the topside anyway. I bought the cap from RS components.

[stj]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

still got the old one?

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

I do indeed.

Edit: took a picture and attached it to the post of the old green one next to one of the new ones.

[stj]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

i cant see the series on the teapo - whats printed on the other side?

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

SC I guess. Other side says "SC105°C" then "10/03" under that and "A3" under that.

[stj]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

1080ma 0.065ohms
1250ma 0.041ohms

i suppose it's possible the esr is too low, but that would be a poor design.
if that is the case then a YXG is very close.

try putting the old one back to see if the noise stops.

[sean0118]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

Is the sound really high pitched? Could be coil squeal.

(If you removed the grey silicon that was gluing the inductors it may have caused it)

https://en.wikipedia.org/wiki/Coil_noise

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

try putting the old one back to see if the noise stops.

OK, so with the old cap back in, testing it jumpered I couldn't hear anything from it except for the fans, so I figured I should test it with a load since that's when I heard the noise last time, so I hooked it all up to the Mac and sure enough under load it is still squealing.

Is the sound really high pitched? Could be coil squeal.

(If you removed the grey silicon that was gluing the inductors it may have caused it)

https://en.wikipedia.org/wiki/Coil_noise

Yes I think you're right, it is coil whine. It sounds not too dissimilar from this video of someone showing coil whine on a graphics card, only it varies quite a lot more in pitch and volume in my PSU depending on what the Mac is doing at the time it seems (just moving the mouse cursor changes the pitch of the noise).

I haven't removed any of the silicon glue anywhere though, the only thing I removed was the cap. I suppose I might have disturbed something when I was taking it apart.

Is this coil whine anything to be concerned about? I suspect once it's all back in it's enclosure and buried in the Mac I probably wouldn't be able to hear the whine much, if at all (then again I do have pretty good hearing, and I'm almost certain it wasn't doing this before I started messing around with it).

[stj]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

maybe a coil was originally resting against something.

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

Possibly. Unless I'm just going deaf in my old age and it actually was doing it before but being enclosed in the case and in the Mac I just couldn't hear it.

If I record it making the noise perhaps some of you can have a listen and verify it is indeed coil whine and not something else though, just to be sure I've not buggered something serious up.

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

Here's an mp3 file (in a zip) of the squealing sound, let me know what you think.

[sean0118]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

Strange, only other thing I can think of is maybe the lower ESR is causing something to oscillate at an audible frequency. Probably unlikely though if it powers up the Mac.

First thing to do would be to measure all the output rails to check they are actually DC 5V etc. You could also try and put your multimeter on AC Volt mode to try and see any ripple, normally though multimeters are too slow for this, you would normally us an oscilloscope.

Also, what do you mean by "testing it jumpered"?

edit: Never mind, I just realised you probably mean jumping the sense pins so that it thinks there's a computer connected

[frantal]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

Hi, my G4 MDD (dual 1,25) did not turn on, nor the power button on the monitor ADC. So I recapped on the PSU C43 (100uF/25) and C60 (1000uF/10). Now the light on power button of ADC monitor turn on, but no chime and no life signs on the computer. Besides this it is very difficult to know where the critical caps are located. I bought all the caps in the list "MDD PS Replacement Caps as Used 20th Oct-2.pdf", but until now only 2 substituted. Could you suggest me where to find the critical on the list, if you have just done this work? I attached label type of PSU and the side where I think there are the "critical" caps. Many thanks for the help...