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Re: All replacement capacitors in iMac G5 PSU burned up

Crazy. More strong support for replacing all caps whether they look fine or not - looks mean nothing! My tech said he had tested the Teapo cap and it looked okay. Now I wonder if he did test it and if so, what he tested for. Disappointing, as many people have told me he is the go to guy in this area.

It sounds like Toasty figuring out the specs on that coil may help many people with the same issue. Thank you!

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Re: All replacement capacitors in iMac G5 PSU burned up

You guys are pretty amazing.

So I can either paint the core with epoxy paint, then rewrap the core with bare 18 gauge copper wire

OR

Leave the core as is and rewrap with insulated solid 18 gauge copper wire.

Is that correct?

What is epoxy paint?

By "insulated" does that just mean it has a rubber(?) coating around it like the black/brown/blue/purple connection wires on the power supply?

As always, thank you....

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Re: All replacement capacitors in iMac G5 PSU burned up

I've checked into the ATX option - many others have done it. With an ATX extension cable, you can cut off two pins on one end, switch a couple other pins and leave the 24V that powers the display disconnected. Then you need an external monitor which defeats the purpose of the iMac. It is an option, though.

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Re: All replacement capacitors in iMac G5 PSU burned up

The measurements on the wire were 1mm, .0395in so I think it must be 18 gauge.

I went to an electronics recycler today and looked through a few power supplies. It is a needle in a haystack goose chase to find a matching inductor. I could have opened power supplies all day but they were not keen on that idea and I wasn't really, either.

Unless a supplier can provide a match for the gauge/turns/core dimensions specs I have, I'm reduced to buying a used working PSU as suggested elsewhere and having...

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Re: All replacement capacitors in iMac G5 PSU burned up

For Toasty - no damage on that disc capacitor - just a drip from when the putty was originally applied.

I'm not able to follow the last few technical posts but I gather that it may be likely that other components have been ruined and that fixing this coil will be ineffective for that reason.

-Nate

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Re: All replacement capacitors in iMac G5 PSU burned up

Thanks for the thoughts i4004. What I meant to ask is does the replacement inductor need to be coated, or is a non-coated (i.e., bare wire) inductor acceptable.

-Nate

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Re: All replacement capacitors in iMac G5 PSU burned up

Also, also - the wire on the burned inductor appears to have been black by design - not from damage according to the photos on Jim Warholic's page. Does that mean the replacement inductor also needs to have black-coated wire?

Is it possible I shorted the inductor by scraping away the black coating on the inductor wire with the exacto knife revealing the bare wire?

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Re: All replacement capacitors in iMac G5 PSU burned up

Also, when Toasty says "check voltages" with the PSU disconnected and then connected from the load, what do I need to do?

-Nate

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Re: All replacement capacitors in iMac G5 PSU burned up

More info per Toasty's request. The black square component mounted to the heatsink has the following on it:

ON (in a circle)
MBR2045CT
CO(or zero)413
aka

The inductor on that side of the heat sink has a couple black spots on two of the windings - I don't think it is damage but could be. I'm not sure if the windings on the badly burned inductor were black originally (some kind of coating) but they are completely black now.

So far, info on the burned inductor -...

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Re: All replacement capacitors in iMac G5 PSU burned up

So the so-called electronics shop does not carry inductors. At Mouser on the net, the inductor search filter asks for a whole pile of specs I don't know - can't specify by number of windings or gauge of wire of course. I looked up a few 10 and 15uH capacitors and they only show generic gif files of the same inductor for every toroid. I am therefore stuck until I can somehow figure out how to get to old electronics boards hunting for a coil with same number of windings, gauge, core type and size in the hope that it matches....

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Re: All replacement capacitors in iMac G5 PSU burned up

I stopped by the hardware shop today and then Radio Shack and borrowed multi-meters at each place to test coil. When set to ohms, I got a reading touching both ends to the core (not the wire) so core is metal. When I touched one end to the inner part and one to one or the other of the leads on the backside of the board, sometimes I would get a reading and sometimes not. Not sure if I just don't know how to use a meter correctly or if that represents an intermittent short. I plan to hit a decent electronics shop 30 miles south...

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Re: All replacement capacitors in iMac G5 PSU burned up

The one unreplaced cap is a real bear to free, which, since it looked okay was not replaced. I believe the tech tested it in place but I need to verify that.

-Nate

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Re: All replacement capacitors in iMac G5 PSU burned up

Yep, under load, that coil heated up right away. The computer worked fine but I shut her down.

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Re: All replacement capacitors in iMac G5 PSU burned up

Sorry for the inductor spec question - didn't see there was a page 2 of replies.

In reponse to i4004, replaced caps only because computer would not power up. 7 secondary caps looked swollen and a couple had a little brown stuff at the top. No smell prior to repair. The coating on the coil was cracked and split before repair but not black at all.

I definitely had to get in and around the coil with an exacto knife to clear all the putty that was in there so the caps could be freed. Could it be possible...

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Re: All replacement capacitors in iMac G5 PSU burned up

What specs do I need to know to get a proper replacement coil inductor? Is the gauge and number of coils sufficient or do I need more info - H value? Does the core have specs I need to know? What does the +3.3 refer to in kc8adu's post? Voltage?

Thanks again.

-Nate

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Re: All replacement capacitors in iMac G5 PSU burned up

Another member describes the exact same symptom with the same coil in the "power supply and design troubleshooting" forum here:

[url]https://www.badcaps.net/forum/showthread.php?t=5961&highlight=imac[/url]Re: All replacement capacitors in iM...5961&highlight

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Re: All replacement capacitors in iMac G5 PSU burned up

Original caps are labeled LTec. All are LYZ 105C except for one which is TK 105C.

What may look like contact is where the tech scraped at the brown stuff a bit. I don't see any contact on the underside of the board.

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Re: All replacement capacitors in iMac G5 PSU burned up

I showed the board to the tech today. He said that the capacitors were fine, i.e, not burned up - the brownish goo on the underside of the board at each capacitor lead was a material from the soldering process. I don't think the brown stuff was there when I first got it back from repair - did it melt out at high temp? Also, the one capacitor on the low voltage side that was not replaced shows no evidence of brown stuff.

No small caps of the sizes you list, Wizard, were replaced. There are some small ones on the...

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Re: All replacement capacitors in iMac G5 PSU burned up

Thank you for the advice, members.

Does anyone know the stats on the torrid that got really hot? It is at position L8 on the iMac G5 1.6 Ghz 17 inch power supply (Apple part no. 614-0293, AcBel part no. API3PC94) sort of right in the middle of everything on the low voltage side. Is this a part that could fail? Is it the sort of thing I can order?

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Re: iMac G5 power supply w/burning coil

I just posted about this exact thing in another category. I had all the bad caps replaced in the iMac G5 17 inch power supply. Worked fine for 1 day and then burned up - same torrid at L8 fried just like yours.

What the heck?

-Nate