iMac with bulging capaciters

[Mettiu]

Hi, I have a first generation iMac G5 20", which is affected by the issue of bulging capaciters. Since lately I started getting the system to hang sometimes, I decided to substitute the bad capaciters with new ones.
So I took the iMac logic board to an electronic repair center and I had the five Nichicon failing caps (C3311 C3411 C3422 C3412 C3321) replaced by others (I don't know the brand) with the same characteristics, but now.. the system doesn't boot anymore.
How is this possible?
I have take back the logic board to that repair center but they have no clue... unbelievable..

[willawake]

Re: iMac with bulging capaciters

well since the board is dead it is not because they used the wrong type of capacitors (this would cause instability etc)
neither is it because they installed capacitor with incorrect polarity (this would make capacitor blow)
but probably because they did either shit soldering, leaving open circuit or they damaged a trace or they damaged a thru-hole

you may also consider that there has been some mistake in the assembly of the unit? maybe some cable not connected etc so i would be checking that first

you may also consider reset cmos if those units have this feature

i see they replaced 5 failing caps. if i recall correct, these units have many caps of the same failing brand/series. all caps 470uf and above of the same failing brand or other shit brand/series should be replaced, otherwise satisfaction not guaranteed

if a repair shop release dead repairs to customer then they are not reputable shop because it means they make no testing

[Mettiu]

Re: iMac with bulging capaciters

Thanks for your answere willawake.
Well, considering the disassembling/assembling of the unit, I have done it myself and I am 100% confident it was done correctly. Morehover, to test the functionality of the logic board, it is neither necessary to assemble everything, you can just connect it to the power supply, use the power on/power off buttons on the mobo and check if all the 4 leds light up consequently. I get only the first two leds on, which means that no voltage arrives to the cpu.. it stops just at the caps I got substituted.

On this logic board there were "only" five caps from Nichicon, all the other ones are non-failing ones.

And I completely agree that the place I went is not a respectable one. But now I am in a small city in Italy and that is the only one..

[Newbie2]

Re: iMac with bulging capaciters

Post some good pictures on the replacement capacitors that the repair shop used. Post a picture of the replacement capacitors, and post a picture of the underside of the logic board where the replacement capacitors went into (it is noticeable since human-made solder joints with normal solder look different than the other solder joints from the Apple factory).

Possibly the repair shop people only knew how to correctly solder on a regular single-layer PCB (found in power supplies for example) and messed up the job on the logic board's much harder to solder on multi-layer PCB by lifting traces and/or damaging through-holes. Another reason could be that they did not handle the logic board with ESD precautions, killing the logic board by pure static electricity.

[Mettiu]

Re: iMac with bulging capaciters

Here the requested pictures, I hope they're sufficient:

http://xoomer.virgilio.it/m.a.t.t.e.o/DSCN0596.JPG

http://xoomer.virgilio.it/m.a.t.t.e.o/DSCN0597.JPG

http://xoomer.virgilio.it/m.a.t.t.e.o/DSCN0598.JPG


Note that the shop originally installed 6 caps, filling the original vacant position too.
After they noticed they removed 5 caps and installed 6, they removed the last one.

[willawake]

Re: iMac with bulging capaciters

Attenzione linky no good

[Newbie2]

Re: iMac with bulging capaciters

Dead links.

Go host your images on ************* if you don't like your current hosting service, ************* is a reliable image hosting service that I use.

[Topcat]

Re: iMac with bulging capaciters

I see G4's and G5's all the time with roasted nichicon HN series caps. After recapping, I've never had one end up as a dud, or so I'm told by the client. I am not able to test them, so I always follow up after it's returned to make sure it worked.

[willawake]

Re: iMac with bulging capaciters

ok i see, link not permitted
i dont see anything interesting
the caps they put i cannot recognise the brand probably shit
but that should not be a problem initially

there is some perhaps slipping of the iron but on the front and back there is only ground planes. i would suggest to remove clean the holes and resolder new caps. if there is still problem then i guess thru hole damaged?

[kc8adu]

Re: iMac with bulging capaciters

i would lean toward sloppy work.
if it still ran there is no reason for it not to after the recap.

[willawake]

Re: iMac with bulging capaciters

Note that the shop originally installed 6 caps, filling the original vacant position too.
After they noticed they removed 5 caps and installed 6, they removed the last one.

i dont get this. it is obvious why the 6 is not needed but again i dont see why any addition would cause damage

[Mettiu]

Re: iMac with bulging capaciters

Thanks for the replies.
I'm sorry, it seems that the link I have posted don't work if you just click on them. However, a copy and paste on the address bar would allow to see them.

willawake, yes I don't think neither that the addition of the sixth one would make any differences, I just reported the fact for scruple.

[Newbie2]

Re: iMac with bulging capaciters

It's okay if they're generic capacitors of the same 1000uf 16V value and 105c temperature rating, but those solder joints are horrible. If you know how to solder and have the right equipment to do the job (soldering iron of at least 60W and some 60/40 or 63/37 solder), then fix those solder joints as they're the obvious reason to why your iMac isn't working. If the solder joints were done properly, your iMac would be in working condition right now.

The addition of one extra capacitor wouldn't have done any damage to the iMac, actually if you remove it in a sloppy way it can do actual damage that can disable the logic board from working.

If you don't know how to solder or don't have the right equipment, then bring it back to that repair shop and tell them about the solder joints. If they're a good business, they would fix those solder joints for you right away and show you the new solder joints.

To aid in your knowledge, here are pictures of good proper solder joints (in a volcano shape and nice and shiny):






Also, some inexperienced technicians will trim the leads too close to the solder joint, and that mistake will effectively kill the connection between the PCB and the component.

[pentium]

Re: iMac with bulging capaciters

I got a similar imac coming in tomorrow or Tuesday.
If it has the same issue, I'll post photos.

[Mettiu]

Re: iMac with bulging capaciters

Since I have never sold neither I got the instruments to do it, I am going to take the logic board back to that repair shop, thanks everyone for the support.
I hope they'll do a better job and I'll get my mac working again!

[Wizard]

Re: iMac with bulging capaciters

You don't understand the issues.

The issue is type of capacitors they initially used.

The ones they use always used general purpose. The computer stuff requires LOW ESR
and high current capablity for switching voltage regulator to cut down on spikes.

I suggest order caps from here and have them use them to replace the incorrect caps.

Cheers, Wizard

[Newbie2]

Re: iMac with bulging capaciters

You don't understand the issues.

The issue is type of capacitors they initially used.

The ones they use always used general purpose. The computer stuff requires LOW ESR
and high current capablity for switching voltage regulator to cut down on spikes.

I suggest order caps from here and have them use them to replace the incorrect caps.

Cheers, Wizard

I know the cheap generic 1000uf 16V caps that the repair shop used are not the best on motherboards, but they should be good enough for his iMac to POST and load Mac OS X for probably a year or two.

He's in a small town in Italy, so the correct low ESR caps may not be available to him.

[Wizard]

Re: iMac with bulging capaciters

Um, G5 was where P4 was and have current requirements and smallest ripple required.

That is the issue. Keep us updated through. Pictures is helpful.

I tried to use different capacitor on a board and I couldn't get it pass prime95. So I had to redo it correctly with proper capacitors.

Cheers, Wizard

[PCBONEZ]

Re: iMac with bulging capaciters

Early iMac G5 were supposed to have been recalled due to the same HN/HM issue that affects the Dell GX/SX 270/280 and others.
Yours may have missed the recall.

.

[pentium]

Re: iMac with bulging capaciters

Well in the G5 I am looking at it would not power on.
The first thing I check is the PSU as visually the caps on the board look okay. Bingo!

So it looks like the PSU needs to be recapped.
That's the problem.
Son of a bitch! Leave it to apple to require a special torx head to open the PSU.
This will take a while to open indeed.