imac G5 PSU cap kit

[pentium]

I just finished pulling the caps out of this thing and here is what I apparently need:

1 x 35V, 330uf, 12mm
1 x 6.3V, 4700uf, 12mm
1 x 16V, 1200uf, 12mm
2 x 10V, 2200uf, 12mm
3 x 6.3V, 1000uf, 8mm

There are some funky caps in this thing that the order form does not have. Also, what specific grade of caps should I use?

[davmax]

Re: imac G5 PSU cap kit

If the caps have vents (weakened by a punched pattern) on the top side use Low ESR caps, Rubycon, Samxon, etc. If no vent use general purpose.

[pentium]

Re: imac G5 PSU cap kit

Okay then, so I'm going with low ESR caps.

Topcat, I sent you an order form.

[KeriJane]

Re: imac G5 PSU cap kit

Hello.

I just recapped a 17" iMac G5 PSU.
The symptoms: THe iMac would not power on and the "Standby Power" LED on the logic board was flickering. (indicating unstable 5V SB power).
This particular iMac apparently had the logic board replaced because all 25 of the Nichicon caps on it look perfect.

The suspect was the tiny PSU. It was held together by Tamper-Resistant T10 Torx fasteners. You cannot find a wrench for this easily, but I got one.

Here's a list of the secondary side PSU caps:

3x- 1000uf 6.3V 8mm x 16mm Ltec, swollen.

2x- 2200uf 10V 10mm x 24mm Ltec, intact.

1x- 1200uf 16V 10mm x 24mm Ltec, intact.

1x- 4700uf 6.3V 10mm x 30mm Ltec, intact. (non-standard size)

1x- 1000uf 35V 12mm x 20mm Ltec, intact. (non-standard size)

1x- 330uf 35V 10mm x 20mm Teapo, badly swollen.

Two of the caps were of non-standard size, the 4700uf/6.3V 10x30mm and the 1000uf/35V Ltecs.

Because this very cramped PSU board does not have the room for a "real" 12x30mm 4700uf cap, I substituted a Rubycon MBZ 3300uf/6.3V 10x22mm.

The 1000uf/35V spot did not have the room for a 16mm "real" 1000uf/35V cap so I substituted a Nichicon PW 1000uf/25V 12x20mm.

I put it all together with Rubycons and the one Nichicon and Pow! It works!

OMG, I fixed it!

Impressions of the iMac G5 running Leopard:
Noisy, slow. Blows lots of hot air out of the back also.

But then I'm spoiled by a quad-core Mac Pro, and the G5 really wants Tiger soooo.....

OMG! I fixed an entire COMPUTER!
An expensive one, too.

Keri

[kc8adu]

Re: imac G5 PSU cap kit

i would measure across that 35v position and verify.
25v may not last.

[Newbie2]

Re: imac G5 PSU cap kit

You can't use a lower voltage capacitor unless you are completely sure that the voltage going to the capacitor is okay for a lower voltage capacitor.

A capacitor put through too much voltage will not last very long.

[KeriJane]

Re: imac G5 PSU cap kit

Hello.

I had checked for the highest voltage that this PSU provides before substituting the cap.

It's 24V, but I'm not sure if this cap is on that particular circuit.

It provides 3.3, 5.0, 5.0 SB, 12 and 24 volt outputs.

It was a 3-way choice-
a- Keep the non-standard Ltec
b- Sub a smaller capacitance at 35v
c- Sub lower voltage and same capacitance.

As the only 35V cap I could find easily in 12mm was 680uf and of questionable heritage, I chose a quality brand of the correct rating and lower (but still at the highest output) voltage.

Maybe I should order up that 680/35 in 12x20mm?

Keri

PS.
Why do these no-name cap companies come up with all of these non-standard sized caps? And why would any reputable manufacturer (of computers, monitors or PSU) specify such a part when they must know that it's a bogus rating?

[KeriJane]

Re: imac G5 PSU cap kit

Hello.

OK, I obtained some NCC 1000uf/35V that are just short enough to fit and replaced the 1000uf/25V. It still works OK!

I obtained a similar PSU on eBay for $10 and recapped it for a spare. It had a 1000uf/25V cap in the same position from the factory!
Also where all the 1000uf/6.3V caps were on the first one are 1000uf/10V.
And the 4700uf position holds a 3300uf.

The second PSU has what appears to be surge protection soldered onto the back of the power cord connector and two nice NCC primary side caps.
They still used Ltec and one Teapo everywhere else though. Several of which got all icky. After a recap this one works nicely also!

I'm disappointed in ACBEL and in Apple for choosing such an inconsistent supplier. Maybe Apple deserves all of the blame as they wrote the specification?

Wondering how I can stuff a Seasonic into my Mac Pro,
Keri

PS. Mac computers often have power status lights on the logic board for the various voltages. After recapping these PSUs any lit ones stay on for a long time after unplugging AC power... it seemed like about 10 seconds! this must indicate a whole lot of capacitance somewhere... maybe the PSU or the 25 or so on the logic board?

[gdement]

Re: imac G5 PSU cap kit

Hello.
PS.
Why do these no-name cap companies come up with all of these non-standard sized caps? And why would any reputable manufacturer (of computers, monitors or PSU) specify such a part when they must know that it's a bogus rating?

The designer probably doesn't worry much about what the standard sizes are, if they know they can get something more ideal as a custom order. They're buying enough volume to get whatever they want.

It isn't just the no-name caps that have custom sizes. I've seen at least a couple different non-standard Rubycon sizes as well.

I also ran into a custom sized Samxon GF in my monitor recently. They needed it because the standard version in the catalog is too tall to fit.

[linuxguru]

Re: imac G5 PSU cap kit

AcBel has been using Ltec for a long time, so they must be OK or the design has a lot of margin and doesn't stress the caps to the point of failure. That said, I'd still have replaced the Ltecs when I had the PSU out, because I suspect they die quietly with no mess like some G-Luxons and Teapos.

1000/35 in 12mm is also available in Rubycon ZL and Nichicon PW - the latter is bulletproof for PSU use.

Edit: If this has an auxiliary flyback converter (found on ATX PSUs, I don't know about Apple PSUs), check all the small primary-side caps in the auxiliary section and replace.

[PCBONEZ]

Re: imac G5 PSU cap kit

I've found bloated Ltec in PSUs.
Also seen them still doing fine in well used PSU's.
I think maybe heat gets 'em.

.

[shiekh@dinecollege.edu]

Re: imac G5 PSU cap kit

I'm way confused; the iMac G5 power supply is:

3.3V 3.1A
5.1V 9.6A
12.0V 9.2A
24.0Vsb 0.33A
5.1Vsb 1.5A

but the caps are 6.3V, 10V and 35V

how does this work? what holds the 12V for instance (which is by far the greatest power line)

[shiekh@dinecollege.edu]

Re: imac G5 PSU cap kit

Correction, there is also a 16V cap

[PCBONEZ]

Re: imac G5 PSU cap kit

Quite normal.
The voltage marked on caps is the MAXIMUM RATING of the cap.
Actual circuit voltage can be anything less than that rating and you are fine.

[shiekh@dinecollege.edu]

Re: imac G5 PSU cap kit

Thanks, I realized that; it was just that when I didn't see the 16V Cap (my fault), I could not figure what the 12V was riding.

[shiekh@dinecollege.edu]

Re: imac G5 PSU cap kit

Just to report that I ordered

3 x Samxon GC 1000uF 6.3V D8 x 14mm
2 x Samxon GC 2200uF 10V D10 x 25mm
1 x Samxon GT 1200uF 16V D10 x 25mm
1 x Samxon GA 3300uF 6.3V D10 x 25mm (original was 4700uF)
1 x Samxon KM 1000uF 35V D12.5 x 20mm
1 x Samxon GF 330uF 35V D10 x 16mm

even thought only the 6.3V capacitors showed damage.

Repaired two power supplies, and both machines are working fine.

[shiekh@dinecollege.edu]

Re: imac G5 PSU cap kit

More news:

As well as the obvious physical damage suffered by all four 6.3V capacitors in the group I found that the 35V 330uF capacitor was down to around half of what it should be (this is the one below the copper heat sink and may have been running rather hot as a result)

I don't have an ESR meter, but if I were to purchase an ESR meter it would probably be this one: http://www.anatekcorp.com/testequipment/atlasesr60.htm