Imac 614-0378 repair advice

[selldoor]

Re: Imac 614-0378 repair advice

Anyone got any thoughts on the live neutral reversed thing I described above?

Cant picture what you mean perhaps a series of pics would help? BUT
have you read the other threads on this PSU.
Do you think it is this brown wire.
https://www.badcaps.net/forum/showpo...7&postcount=20

[villiam]

Re: Imac 614-0378 repair advice

Cant picture what you mean perhaps a series of pics would help? BUT
have you read the other threads on this PSU.
Do you think it is this brown wire.
https://www.badcaps.net/forum/showpo...7&postcount=20

Yes I saw that thread. I think they are talking about the brown wire on the output of the PSU which is some control from the DC-DC board. I mean the blue and brown AC input wires.

I've attached a photo, the wires are out of focus but you can see the colours under the extra sleeve. Notice the brown wire connects to the point marked L on the board and directly to the fuse F1. The problem is the connector that this plugs into has the reverse colours. So the wire from the AC inlet which connects to the point L is in fact the neutral. I have checked continuity to the actual plug pins. It's like the connector was installed backwards at the factory.

[selldoor]

Re: Imac 614-0378 repair advice

Well they are made in China ! I think you are right to be concerned, I dont know but I would guess that if the fuse blew the rest of the circuit would still be live if touched - rather dangerous.

[budm]

Re: Imac 614-0378 repair advice

So the male IEC C14 AC inlet, the brown wire is connected wrong at the AC inlet? Picture of the IEC AC inlet?

[selldoor]

Re: Imac 614-0378 repair advice

Tried to find some more pics but dont think they help.
http://www.guzu.com/ebay/images/DSCN4590.JPG
http://www.jimbodalobster.com/imaca1145powersupply2.jpg

[villiam]

Re: Imac 614-0378 repair advice

No, the wiring appears correct at the board and the inlet, but the connector between the two, (which is keyed for one way only connection), is reversed so that brown->blue, and blue->brown. The PSU side of this connector is just half in the shot at the bottom left of the new photo I posted.

Sorry I can't photograph the inside of the AC inlet without dismantling virtually every thing inside the mac. I haven't seen it so I only assume it is wired correctly by continuity test from its side of the problem connector to the plug pins.

[ben7]

Re: Imac 614-0378 repair advice

I decided I will replace the caps. Hiding under the 420V cap, there is a 25V 68uF which looks suspect, top of the can is bulging a little.

I guess whatever happened can't have done the caps any good so might as well put in some better ones. Nichicon HE series a sensible choice for the 16V parts plus a PZ series for the high voltage cap and an HV series for the 25V 68uF? Mouser don't stock an X2 cap that will fit so I'll leave it for now.

Anyone got any thoughts on the live neutral reversed thing I described above?

Yep those caps are perfect

[villiam]

Re: Imac 614-0378 repair advice

Tried to find some more pics but dont think they help.
http://www.guzu.com/ebay/images/DSCN4590.JPG
http://www.jimbodalobster.com/imaca1145powersupply2.jpg

This one shows where I think there is a problem. On my one, the ringed connector reverses blue and brown.

[budm]

Re: Imac 614-0378 repair advice

OK, I can see where the mistake was made, thanks.

[villiam]

Re: Imac 614-0378 repair advice

Parts arrived the other day, so I started taking out the old caps and continuing the imac theme of "not so pretty on the inside" found a bunch more stuff crammed under the high voltage cap including, grrrrrrr, another small electrolytic. You can see it in the pic, (C21), and maybe also see the first small one I mentioned looking a bit bulgy on top, (C32). Have to wait til tomorrow before I can finish soldering.

I used a multimeter continuity/diode test on those two diodes under there. The large tested normal but I'm not sure about the small one. D11 tests like a normal diode in one direction but a much higher reading one in the other? Is this normal for a zener or something? I can't read the markings easily due to grey goo residue.

[ben7]

Re: Imac 614-0378 repair advice

Parts arrived the other day, so I started taking out the old caps and continuing the imac theme of "not so pretty on the inside" found a bunch more stuff crammed under the high voltage cap including, grrrrrrr, another small electrolytic. You can see it in the pic, (C21), and maybe also see the first small one I mentioned looking a bit bulgy on top, (C32). Have to wait til tomorrow before I can finish soldering.

I used a multimeter continuity/diode test on those two diodes under there. The large tested normal but I'm not sure about the small one. D11 tests like a normal diode in one direction but a much higher reading one in the other? Is this normal for a zener or something? I can't read the markings easily due to grey goo residue.

D11 seems like it has a 'UF' prefix, so its some sort of high-speed diode. I doubt it would be bad. BUT, did you measure it in circuit? Measuring in circuit is not very useful, as other components will give you false readings on one component.

ProTip:

Having a large bin of extra bits and bobs will help a lot for fixing things

[villiam]

Re: Imac 614-0378 repair advice

Ah, I was hoping it was testing in circuit that might have caused the funny readings. I didn't really want to desolder anything that I would have to put back in, but wanted to make sure those diodes were at least not short or open. I'll continue my optimism and assume they are fine for now.

I should have this thing back together tomorrow night, can anyone tell me how to test it without reconnecting the imac? Will it turn on with no output connected or do I have to trick it in some way?

How about testing the imac, can I just plug 12V from a suitably rated ATX into the imacs DC-DC board?

[villiam]

Re: Imac 614-0378 repair advice

Success, imac is going again. Thanks for all your advice.

Guess I got lucky and the protection parts did their job by blowing up. New fuse, MOV, rectifier and all electros replaced. Also swapped the live and neutral the right way round, urgh, that turned out to be a horrible hassle, I wish I hadn't spotted it. I very nearly botched what should have been a simple repair but at least I didn't send it out my factory door like that.

Anyway, all seems well, except now the optical drive appears to be knackered so I still can't button it up and get rid of it.

[ben7]

Re: Imac 614-0378 repair advice

Success, imac is going again. Thanks for all your advice.

Guess I got lucky and the protection parts did their job by blowing up. New fuse, MOV, rectifier and all electros replaced. Also swapped the live and neutral the right way round, urgh, that turned out to be a horrible hassle, I wish I hadn't spotted it. I very nearly botched what should have been a simple repair but at least I didn't send it out my factory door like that.

Anyway, all seems well, except now the optical drive appears to be knackered so I still can't button it up and get rid of it.

Congrats on fixing the PSU

[RobotHamster]

Re: Imac 614-0378 repair advice

I found this thread while trying to ascertain the voltages on the out pins of this model psu.

I thought that I would post here since I have exactly the same psu and I foolishly didn't check it's position when I was testing it and a point shorted to earth with a part in the case.

A picture of the damage is attached. I was just wondering if there was any idea on salvaging this psu as it turns out the one it was meant to replace (a celetronix version) is not actually fried as I was told - by a 2 separate people who repair computers for a living - as it outputs approx 12V across the black/grey wires and around 4v brown/black and 8v brown/grey (which I'm damn sure is right).

I am rather new to the bare hardware and was wondering if this could be salvaged - if it was just a short a fuse should have blown but I've been told the fuse is not on the live wire for some insane reason as if that was the case I could have likely just replaced a fuse as it would have fulfilled its purpose.

So if anyone could suggest something

[Toasty]

Re: Imac 614-0378 repair advice

Picture is jiggly

I see the scorch mark. What is wrong with this PSU? You talk of the other it is meant to replace, but not about this one's issues...

Also see:

https://www.badcaps.net/forum/showthread.php?t=15205

and post 40:

https://www.badcaps.net/forum/showpo...0&postcount=40

This is a 12v PSU, nothing else. Other voltages you are measuring are not part of its' specifications. They are inputs and signals to the motherboard.

T

[ben7]

Re: Imac 614-0378 repair advice

^ That looks like a bad solder joint has arced there! :O
May be an easy fix :shhh:

[RobotHamster]

Re: Imac 614-0378 repair advice

Well, I have discovered that the kettle lead supplying the iMac fused so there may not be lasting damage with the PSU. The strange thing is that I tested the old psu before the new one and it appeared to output the correct voltage on the blue/grey rails but after the short the new one did work (unsurprisingly as I have found out that there was no input voltage) but the old one still outputs the correct voltage.......

Obviously there is something else going on here and I will investigate further. Unfortunately the kettle lead I used was from my ps3 so I will need to replace the fuse tomorrow.

[sudakarman]

Re: Imac 614-0378 repair advice

Thanks budm, I'm not sure about the position of this MOV in the circuit, it is a small disc ~5mm, doesn't seem to be directly across the line input. I've attached some photos showing the position of the damaged components I have removed. Any experienced eyes spot any other signs of trouble on this unit?

Any tips on how to proceed with the repair would be welcome, I have some electronics experience but next to none with switching supplies. My plan at the moment is just to replace the rectifier and fuse and see what happens. Do I need to do something on the output side to make the supply switch on without the computer connected?

Also, how would you suggest testing if the rest of the computer has survived. This PSU seems to only output two 12V rails to the DC-DC board with some kind of control signal returning on the brown wire. Is it wise to just connect up another 12v source to this and see if the rest of the computer is alive?

Dear Villiam,

Do you have schematic of API4ST03-291 power supply if you have please post

Regards
sudakar
Thanks in advance