IMAC 24 PSU Bad Caps replacement

[Francisco.s]

Re: IMAC 24 PSU Bad Caps replacement

What voltage is the MOSFET driver supplied with? Is this the original MOSFET too?

What have you done to the optocoupler control? That may be the problem.

The mosfet is the original one, the pulse driver are right also. (I will have to check with osciloscope, and post the value)
I feed the optocoupler with some aditional voltage, from one of the windings, to make sure that no overvoltage is generated by the psu. (an is the only way I have found to keep the controler IC sending pulses to the mosfet)
I have in mind some other test, I will post.
Regards.

[Francisco.s]

Re: IMAC 24 PSU Bad Caps replacement

The mosfet is the original one, the pulse driver are right also. (I will have to check with osciloscope, and post the value)
I feed the optocoupler with some aditional voltage, from one of the windings, to make sure that no overvoltage is generated by the psu. (an is the only way I have found to keep the controler IC sending pulses to the mosfet)
I have in mind some other test, I will post.
Regards.

Hi, have good news. I have found a diode, (d6) in bad state, (leakage) it is a special one (1N6303A, TRANSIENT VOLTAGE SUPPRESSOR) that is connected in parallel to the primary winding of the main switching transformer.
I hope next week, have it already repaired.
Note: it's difficult to to get access to this diode, due to its location. (hidden under thermal heat sink)
I'll continue posting results.
Cheers.

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

BUMP!

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

@ Francisco.s - What is R83 markings? Do you have a photo of that area?

Thanks!
T

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

@Francisco.s - Disregard. I re-read your post and see that yours is also burnt.

Does anyone have this PSU or system and would be willing to open it and get the marking from it? Pleeeeease

T

API5ST06
API5ST06-290
API5ST06-290G
API5ST06-291
API5ST06-291G
614-0402

NOTE: Possibly similar or compatible units - Apple P/N : 614-0386, 614-0387, 661-4183

[noog1234]

Re: IMAC 24 PSU Bad Caps replacement

Hi All, have similar prob with my sons IMAC 2111. Led1 ON, Led2 ON, Led3 flashes once and then OFF, Led 4 OFF. I'm a bit of an amateur so hesitant to delve deeper. Other forums suggest verify Video card then verify mother board. I guess this is done via substitution? I will take apart and look at the PSU to see if the caps are OK, and after that check the mother board caps. Any other ideas appreciated

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

See: http://forums.macrumors.com/showthread.php?t=1018187

Try the RAM and check the graphic card. (Nvidia 8800GS)

Go to Apple before you start taking it apart.

The PSU is okay with that many LEDs on.

T

[noog1234]

Re: IMAC 24 PSU Bad Caps replacement

Thanks for the info, I read the link it seems to be a common prob. My son has already had the PSU replaced but now out of warranty. In one of the posts in the link, they mentioned bad RAM I checked the seating and is OK. Is it alright to power up the IMAC with no ram installed?

Cheers

[joen_d66]

Re: IMAC 24 PSU Bad Caps replacement

hello all,,i got 4 this PS.same problem but almost resolve.can somebody give m11 component datasheet.marking code SPAK...thanks before

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

Got one in! Only mildly toasted...

R83 code is 66A = 475Ω

T

[noog1234]

Re: IMAC 24 PSU Bad Caps replacement

See: http://forums.macrumors.com/showthread.php?t=1018187

Try the RAM and check the graphic card. (Nvidia 8800GS)

Go to Apple before you start taking it apart.

The PSU is okay with that many LEDs on.

T

Well you wouldn't believe it. Today I removed 1 of the ram modules and the machine powered up and worked. So I shut down, re-inserted the ram module and it powered up and worked. Problem fixed...no way tried again a few hours later on and nothing, absolutely nothing...mmmm. No power indicator. I hate intermittent faults.. Any ideas?

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

Make sure something isn't shorting to the chassis frame when you apply pressure to the RAM slot or PSU connector. You started with indicator LEDs, but now have -none- ??

Unplug the PSU from the chassis/mobo and wait 15 mins then plug it back in and see. Same with RAM.

No clue from here.

T

[noog1234]

Re: IMAC 24 PSU Bad Caps replacement

thanks will try after work

[noog1234]

Re: IMAC 24 PSU Bad Caps replacement

Unplugged unit from mains, next day it powered up ok everything working. Shutdown from OS screen. Left plugged in and mains on. Next day tried to switch on but no go, no power indicator on machine. Unplugged from mains, and will leave for a few hours and try and power it up again.

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

Sounds like a PSU problem (again!)...

One or more of the caps is/are just good enough when it's cold to get it going, but fail after it's been on for a while.

Pull it out and have a look. Probably some bulging ones as seen in previous posts on this thread. Recap parts shouldn't be more than $20 US including shipping.

Pics would be good too.

T

[noog1234]

Re: IMAC 24 PSU Bad Caps replacement

Thanks will give it go and post any relevant pics

[2lostkiwis]

Re: IMAC 24 PSU Bad Caps replacement

In case anyone is interested, I had a 614-0402 power supply that was also suffering from swelling/ruptured caps. I replaced all 7 caps with the following:

C4, C2? (next to C4)
original: 1500uF 16V, LTEC LXY
replacement: EEUFR1C152 panasonic, element14 1800639

C44, C45
original: 1000uF 16V, LTEC LXY
replacement: EEUFR1C102 panasonic, element14 1800637

C46
original: 680uF 16V, LTEC LXY
replacement: EEUFR1C681 panasonic, element14 1800636

C55
original: 220uF 35V, LTEC LZG
replacement: EEUFR1V221 panasonic, element14 2217565

C39
original: 1000uF 35V, LTEC LZG
replacement: EEUFR1V102 panasonic, element14 1800671

But the supply would still not start. The PFC appeared to be working (gate drive pulses to fet). The NCP1381 had a supply voltage on it when measured with a meter. R83 was toasty but still measured the correct 475R.

Anyways looking into the supply to the NCP1381 with a scope, and lots of drop outs (below 10V which I think is the under voltage lock out). So traced this back to a mains resistor diode fed capacitor supply that was faulty. It is C32 47uF 35V LTEC, replacing this brought the PSU up but then it shut down. Next to C32 is C33, the same cap but a different rail, it tool was also faulty. Replacing this cap also returned the power supply to normal operation. The two caps are located under a heatsink near the fet for the PFC circuit. They were both covered with lots of grey silicone.

Hope this might help someone else.

[m1rhodes]

Re: IMAC 24 PSU Bad Caps replacement

I also have the same power supply, gone bad.
Did anyone ever find out what the correct values for C54 and R83 are? Or a schematic of this psu?
My wife wants to try to repair the board, but hard without the proper values.
Thanks in advance

[Toasty]

Re: IMAC 24 PSU Bad Caps replacement

R83 = see post 70 above ^^

Don't remember where C54 is or what it is. Location, please?

T

[m1rhodes]

Re: IMAC 24 PSU Bad Caps replacement

C54 is directly above R83 (See pic #2 in post #34)
Both are smoked on my psu, and unreadable.
I'm poking around ebay to see if I can find a matching computer with a working power supply so I can pull values to try to repair this unit. May end up with a few spare parts