Alright, here we go again!! This is a first generation iMac G5 (the last one was a second gen). This was one of the donors given to me by a fellow forum member here. I wanted to get one cranked out right away, just so he doesn't think his contributions were for nothing!
The changes in polymer caps from the previous one are that I used 1800uF 6.3v Nichicon LG series caps in place of the 1800uF 6.3v lytics that it originally had. I used 1500uF 6.3v UCC polymers in the last one, and it worked without a hitch, so I didn't foresee any reason why I would have any trouble here. I did one of the 20" ones first. My plan was to do both poly revisions on each size iMac. When the deal was worked out with the donor, I didn't have the other 20" I used in the other experiment, so he donated 2 of each. Now, I have a spare 20".....
Anyway, onto the project:
Getting ready to start:
Back removed. The motherboard had no bad caps, amazingly enough, there were actually some good Nichicon HN series caps in it. The date code was 0422 (made in the 22nd week of 2004), they should have failed by now! Pre-testing, this system actually would POST.
Crack open the Ac-Bel PSU (might as well start at the beginning), and tadaa!! there's the bad caps! I'm surprised it would even POST like this.
Recapped in Rubies:
Junk L-TEC caps:
Revived PSU:
Now onto the logic board. I was shocked to see the original caps were still good, even the rubycon's. I've seen these heaters cook rubycon and UCC lytics many times.....I was amazed beyond words that the HN's were still good as well, those would fail under normal operating conditions, forget about extremely heated conditions. All the caps on this board were original, it had not been recapped previously.
The 'miracle' nichicons:
Unbloated rubies:
I'm getting to the point I can have one of these apart in about 10 minutes....
...and the polymer goodness!
Nichicon LG series:
Some 330uF 16v UCC's replacing the 1000uF 16v HN's:
Back together:
It POST's:
...and OSX being installed:
it's up and running now, and another iMac polymodding experiment seems to be successful!!
Keep in mind, the primary purpose of these experiments is to see what will play nice in these systems as far as polymers go. Longevity testing is rather nill, as in a heat-stressed environment, polymer caps will outlast even the best lytics on an exponential scale, so that's not a mission objective here. By the time the polies would fail, we'd all have long white beards anyway. I just wanted to make sure that the poly mods and alternative capacitor values didn't compromise stability in any way.
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Re: The "Indestructible iMac" v2.0 - Poly revision 2
Here's the same rework above, except done on a 17" model this time. The 20" seems to be a little easier to take apart, but they're both pains in the asses.....worth the effort though.
Anyway, onto some pics:
PSU with more toasty L-TEC craps:
Logic board with popped UCC caps:
Some poly goodness:
If you know anything about aviation, you know what the term "3 green" means.....in iMac talk, it means 3 green LED's and a working system!
OSX 10.5 installed (1.8GHz 1GB ram, runs great)
With this experiment drawing to a close with great success, keep your eyes peeled for the official release of the Badcaps.net iMac full polymer kit!
Re: The "Indestructible iMac" v2.0 - Poly revision 2
Quote:
Originally Posted by ratdude747
maybe you should sell a PSU recap kit as well... if it is not pre-included already.
put a really bold note in the descrition of the kit.include a link.
seems every one i have recapped had a sick psu too.
i would do the board and it would be fine here.customer reinstalls it and its about as stable as charles manson.send me the psu and its blown to hell.if your cap kit customers are willing to do the mobo the psu is easy.
Re: The "Indestructible iMac" v2.0 - Poly revision 2
Seems AcBel has a million different revisions of these PSU's. I have 8 of them (donor sent 4 spares with the systems) and nearly every one of them has a different cap configuration... I never realized there was a difference between the 20" and 17" PSU's.... The 20" PSU is a little thicker, but even PSU's intended for the same size iMac's are different internally. Kind of hard to make a kit for the PSU...
Re: The "Indestructible iMac" v2.0 - Poly revision 2
I'll have to look and see. I didn't look at the model numbers of them, I just recapped them all, and they all worked. I have 4 spare acbel imac PSU's, 2x 17" ones and 2x 20" ones.
Re: The "Indestructible iMac" v2.0 - Poly revision 2
true but you and i are spoiled by just opening the bins and grabbing what is needed for the job at hand.i noticed several revisions of these but since i dont have time to make kits i never thought of the difficulty in making one.
i will track and post the parts list on the next ones.
Quote:
Originally Posted by Topcat
Seems AcBel has a million different revisions of these PSU's. I have 8 of them (donor sent 4 spares with the systems) and nearly every one of them has a different cap configuration... I never realized there was a difference between the 20" and 17" PSU's.... The 20" PSU is a little thicker, but even PSU's intended for the same size iMac's are different internally. Kind of hard to make a kit for the PSU...
Re: The "Indestructible iMac" v2.0 - Poly revision 2
Is it from a first generation 20" G5? When you say "dead one," do you mean no 5vsb on 9 and nothing on 22 when it's plugged in but not jumpered (15 to 16)? The 661-3350 replaces all the variations Apple put in those first machines. Apple's GSX doesn't even list the older numbers... just the 661-3350. If you have recapped already, check the underside and look for Q1 near the PWM. An E-C short will keep the supply from turning on.
Re: The "Indestructible iMac" v2.0 - Poly revision 2
those are the 12V input filter caps.
they're basically additional filter caps for the power coming from the PSU..
most normal computer mainboards with polymer caps from the factory have such low values as standard.
haven't seen any new(-ish) PC mainboard with 12V input filter poly caps with higher values than 470µF 16V x4
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Re: The "Indestructible iMac" v2.0 - Poly revision 2
Topcat, why do you only sell 1500uF polys as part of kits and not separately? I use 1500uF polys on motherboards not mentioned in your kits (Like in my thread on the GA-7VA-"DS3L")
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Re: The "Indestructible iMac" v2.0 - Poly revision 2
Quote:
Originally Posted by meanderer
What's the reason to lower the caps value from 1000uF to 330uF?
What functions do they serve in the circuit that allows such swap?
IIRC, ESR is a lot more important than capacity in switchmode supplies. If you can get lower ESR caps you can make it with lower capacitance and still keep the same level of ripple. Some might argue that transient response may be compromised because the caps are too small, but for one this is a computer and it doesn't have high level transients, and secondly it's the job of the control loop to keep voltages stable during those transients.
The "Indestructible iMac" v2.0 - Poly revision 2
Linear Mode
