Any tips for my first recapping? (iMac G5)

[moonhack]

So, I finally decided on that I wouldn't lose a lot if I tried to recap this 17" Rev. B iMac G5 with a logic board full of blown capacitors... I've had it on storage for around 3 years now since it was given to me, and maybe I should fix it. Why? Because I now have a working G5* which I love and works just perfect in 2013, I have thought up a couple good uses for this to-be-fixed machine. I originally had bought a recapped board from eBay but it somehow turned out to be DOA (it looks completely fine with a good soldering job yet the 2nd LED won't even flash (long story short, seller got defensive, was dumb not to report him, he disappeared, never got a refund)). I recently tested the logic board with the busted caps with the power supply and the 3 LEDs lit up without hesitation (though I know the screen won't turn on because of the caps), so I thought I should try fixing it. I can't open the Delta Electronics power supply but as far as I can see it's all good inside.
Now, I have ordered the capacitor kit and have seen videos and guides on how to solder and desolder... last time I tried to solder something onto a motherboard years ago I killed it, though, so I don't have a lot of confidence yet.

I have seen different opinions about recapping this particular board. What advice/tips could you give to a total noob? 40W, 45W, 75W, or...? Desoldering pump or dremel? Flux-core solder or lead free? Anything else I need to know?

Thanks a lot in advance!!!



*I also have a question about this one: All its capacitors are Rubycon K-vent MCZs and are all fine. The power supply is a Delta one. It was very dusty inside when I first got it so I suppose it was well used before, and it works perfectly, so will these caps be okay or should they be replaced? They're rated for 105C and the CPU temp oscillates between 51-72C (max when under full load, not all the time) so... what do you think?

[JoeyJoe]

Re: Any tips for my first recapping? (iMac G5)

Personally I use a 30w iron with a fine pointed head, a solder pump and some thin solder. It all comes down to personal preference but I find it easier to use. I also found out the hard way to always use decent capacitors. I will always use Panasonic from now on.

[kc8adu]

Re: Any tips for my first recapping? (iMac G5)

a 30w fine pointed iron will not do the job!
these imac boards require lots of heat and even preheating to recap.
lots of heavy power and ground traces that soak up the heat from the iron.

Personally I use a 30w iron with a fine pointed head, a solder pump and some thin solder. It all comes down to personal preference but I find it easier to use. I also found out the hard way to always use decent capacitors. I will always use Panasonic from now on.

[theOracle]

Re: Any tips for my first recapping? (iMac G5)

here is the iron that would be perfect for that Mac job -70W



do NOT use lead free, it will not mix well with the leaded solder of your old Mac, instead you want:

rosin core solder 63/37 (Radio Shack p/n 64-015 or equivalent)
rosin solder flux (Radio Shack p/n 64-022 or CAIG DeoxIT rosin flux p/n RSF-R80-2)

[moonhack]

Re: Any tips for my first recapping? (iMac G5)

Thanks for the replies!

theOracle: Could a cheaper 60W iron like this do the job? One like that is easier to find for me...

[theOracle]

Re: Any tips for my first recapping? (iMac G5)

I think I would pass on the cheap Chinese knockoff - good tools get the job done, crappy tools just waste your time, burn up your computer, and raise your blood pressure - the one I recommended will still be working when you are in the ground! - It's a smart investment - otherwise are going to end up buying it anyway, when this other thing isn't cutting it. - If you can find a better deal on a Weller WES51 - that would be nearly as good as the Hakko

[theOracle]

Re: Any tips for my first recapping? (iMac G5)

~

[momaka]

Re: Any tips for my first recapping? (iMac G5)

Thanks for the replies!

theOracle: Could a cheaper 60W iron like this do the job? One like that is easier to find for me...

I've used cheaper irons like that. They are okay. Definitely not as good as higher quality irons, but yes, they will do the job once you get used to some of their quirks. If you have nothing else available, go for it.

[Uniballer]

Re: Any tips for my first recapping? (iMac G5)

I suggest you get a dead motherboard from a PC or Mac and practice pulling parts and reinstalling them. If you're going to wreck a board building up your skills make sure it is one you don't care about.

I like the Hakko FX-888D, too.

[y_not]

Re: Any tips for my first recapping? (iMac G5)

do NOT use lead free, it will not mix well with the leaded solder of your old Mac.

Oracle, I must respectfully disagree with that statement, but not in the sense of practical application, only that iMac G5s in fact DO use Pb free solder. I know 1st hand.
Which is what further adds to the immense PITA factor of repairing them.
However, I do agree with the rest of what you posted.
I will add and to clarify against any confusion, that leaded solder mixing with existing lead free solder joints is wise, as it improves wetability of the joint in both desoldering and resoldering operations, simultaneously lowering the overall melting point of the joint as the 2 alloys mix into a new, lower melting point alloy.

I would advise an iron though with a MUCH LARGER heat reserve for those massive ground planes on that board.
That Hakko iron is reportedly a very good iron for most work, although I have no direct personal experience with it. But this I fear is too large of a work piece, sapping heat much too quickly from the iron.

Lastly, liquid flux is A MUST! Especially with these Pb free joints that JUST DON'T LIKE TO MELT! True, I have done, as have many, plenty of joints without it, simply relying on the rosin flux core of the solder spool being fed into the joint. But there's always those stubborn joints with just a bit too much oxidation, often not even any visibly different to the naked eye, that without an initial application of liquid or paste flux, DO NOT MELT!
Pb free is even more fussy, good or bad oxidation, either way, those high temp melt joints flow much easier with the adl. flux, aside from the solder core, than without.

[theOracle]

Re: Any tips for my first recapping? (iMac G5)

I was probably thinking about Mac G4 being leaded

I am going to have to respectfully disagree with your insistence that AS5 must only be applied with a credit card or paper bag or whatever. As the guy who invented overclocking in the early 1980's - I have always applied thermal compounds (including enough AS5 to paint a bedroom) with my freshly 91% alcohol-washed completely oil-free index FINGER!

and since I get the coolest CPU and GPU temps of anyone I know, I am thinking it works fabulously!

will agree that most folks use way too much though!

[120volts]

Re: Any tips for my first recapping? (iMac G5)

Did you ever get around to pulling the caps?

[moonhack]

Re: Any tips for my first recapping? (iMac G5)

Well, at the end I decided it would be cheaper to get somebody with the proper tools and more experience to replace them, and so he did… strangely enough, it behaves exactly the same as before?
That is, the white light comes on, nothing appears on the screen, the light stays on, and after a little while the fans come on at full speed. The third led never comes on either. What's the deal now?

[moonhack]

Re: Any tips for my first recapping? (iMac G5)

Ok, update: The repair guy managed to get the computer to boot and it seems very stable now, except for the fact that there's no backlight! Yes, there's image on the screen, but no backlight comes up. What are the chances of it being the inverter instead of the actual backlight or maybe even the logic board?
At least I can VNC into it now.
Thanks!

[ant3202]

Re: Any tips for my first recapping? (iMac G5)

need to test.... a 50:50 case IMO