Another iMac PSU (614-0352)

[oldhat]

Hi everyone, in trade for his repairing an old bicycle of mine, my sister's boyfriend gave me an old broken iMac to see if I could salvage his porn, I mean, data off of the drive. I did that but I wanted to see what the problem was and hopefully revive the machine. Turns out that lots of these iMacs had PSUs with crummy capacitors. Which lead me here.

I noticed that the exact same capacitors blew on this PSU as in the diagram here:

https://www.badcaps.net/forum/showpo...9&postcount=14

Interesting.

Here's my question, now that I know the specs of the capacitors I have to replace, how long should it take me to solder them in? My noobish soldering experience is limited to wiring harness on cars and tinkering with ECUs. I have a cheap Radio Shack iron.

Should I buy a new iron?
What kind of solder should I use?

Also, is there a best way of getting rid of the gray glue/rubber cement stuff holding everything on the PCB? What's it called so I can replace it?

I can teach myself how to desolder the caps using teh Google, I think.

Worth a shot for me to try and fix it? If not, would it be better to take it to an electronics shop and have them do it (and how much should that cost)?

Thanks, sorry if these questions have been asked before. I searched and read the iMac threads.

[etnietering]

Re: Another iMac PSU (614-0352)

You shouldn't have too much of a problem desoldering the caps/soldering in the new ones. That's the PSU board of the iMac, and PSUs tend to be rather forgiving and not very delicate, so noobish soldering skills won't really be a problem. The first cap may take you 10-15 minutes or more, but once you get the hang of things you should be able to do it rather quickly (1-2 minutes/cap).

If you're only doing this one recap, you're probably fine with the cheapy iron. I've done all mine with cheapy irons (15 dollar radio shack iron and 8 dollar ebay iron). I would recommend getting some good solder though. I use the High Tech Silver Bearing solder from Radio Shack. It's 62% lead, 36% tin, and 2% silver. It's a little more expensive than regular solder, but it makes really really nice solder joints and is very easy to work with. Also available at Radio Shack is Desoldering Braid. It's also not very expensive, and very handy when trying to remove components. You can search google to find out how to use that too.

For the glue, I usually just try to pull it off (probably a bad idea, I know), or use some small diagonal pliers to cut it, and small needlenose pliers to yank it off. It's always worked well enough for me, but you may have to improvise. Other people here might have more advice on that. About replacing it, I've heard that regular old hot glue can screw things up, so don't use that. Personally I've never used anything, and haven't had any problems, but I know some people here use it and they can recommend you something to use.

I'd say it's definitely worth it for you to try and fix. For the cost of caps (probably < $10 unless you're replacing the big 200v ones), and a couple bucks for solder, you can have a fully working machine. Even if you totally FUBAR it, you at least gained experience, and know what not to do next time. An electronics shop would charge you many many times that. Taking it someplace would guarantee that it works, but if it's old then it's probably not worth it.

Hope this helps! Let us know if you need help choosing caps - remember to get low ESR/105C caps. Good Luck!

[PCBONEZ]

Re: Another iMac PSU (614-0352)

Fry's Electronics [if you have one] has a decent 60 watt for $10-$15.
They will also have solder and braid.
But just like Rack-shack, their caps aren't good enough.
You need low ESR and neither of those places has them.
.

[oldhat]

Re: Another iMac PSU (614-0352)

Thanks guys. I went by Rat Shack and got the good solder (thanks for the recommendation) and the braid. I was looking through the caps and it looked like a grab bag of different brands and I couldn't remember off the top of my head the long list of bad caps in the FAQ.

Luckily, there's a high quality mom n' pop electronics store in my area:

http://allashers.com/

One last thing, is the problem on these PSUs exclusively on the low voltage side (read: should I pull the big 200v caps off and check them?)

[Toasty]

Re: Another iMac PSU (614-0352)

This units board IS delicate and muxing around without good soldering/desoldering skills and equipment will get you in trouble. It's a double-sided board and you can easily take the top traces off if you're not careful. See Topcats desoldering guide on the badcaps.net home page on the left side. I prefer the rocking method he describes.

<deja-vu> If you're recapping the board, do ALL the caps. You've 15 total on here, so 2 more won't kill you. Should run you about $7 more for both.

I kinda-sorta doubt that the local electronics store will have the low ESR caps you will need for this repair. Likely that the ones they stock are "General Purpose" types. Maybe better than Radio Shack's, but still not correct for SMPS use.

Types to use:
Panasonic - FC, FM - UP or HB for big ones
UCC - KZE, KZJ, KZM, KZH - KMQ for big ones
Nichicon - HM, HN, HZ
CDE - SLP for big ones

Removing the glue/caulk should be done with a plastic implement of some type. You'll have to find what works for you. I use an X-acto knife to remove the bulk material and then a plastic spoon handle (remove the spoon bit) smoothed to fit in the areas. It's nothing fancy but works for me. Replace the caulk with a decent silicone sealant and use it SPARINGLY. You don't have to glob it all over like the original.

Is the supply dead? Have you tested it out of the machine?

Toast

[oldhat]

Re: Another iMac PSU (614-0352)

Awesome, thank you.

Unfortunately I don't have a spare iMac to test the supply in. It is most certainly dead. Two of the caps blew smoke/electrolytic fluid onto the heat shield and the symptoms are exactly the same as other computers with dead power supplies (a faint clicking noise on power-on, rapidly flashing #1 LED on the mobo, no drive spinup, etc.) which makes me think that it's the supply.

Fortunately, I already have his data which is what he cared most about so it's kind of a why not? thing at this point. I'll be careful and attempt this repair. Thanks for the warning about the traces and also the tips about brands and the Xacto knife + silicone caulk.

This store is supposed to be pretty good, they sell to a lot of the UC Berkeley EE guys and homebrew computer people in town. I'll see what they can do and let you know how it goes. I hope it works.

[Toasty]

Re: Another iMac PSU (614-0352)

>>I searched and read the iMac threads.<<



Then you should know how to power it on without La Machine...

Try searching the forums for: imac pinout
Check the box: Show Results as Threads

Toast

[Toasty]

Re: Another iMac PSU (614-0352)



Ever fix it? Any progress?