Apple iMac iSight Midplane Recap

[Toasty]

Question was raised by edbog in "The Good Capacitors Thread".

I'm bringing the question here for him and have noted such in that thread.

Toast

TGCT #49

I received some Rubycon capacitors with the plug at the bottom extended out from the can not quite 1mm. Other than this the caps seem o.k. When soldering to mother board, these caps will not be flush and is this a sign that the caps are defective?

TGCT #50

That's intentional.
Most caps have extensions [legs?] on the bung [rubber plug] to prevent them from sitting directly on the board. This allows cleaning the PCB [not necessarily a motherboard, ANY PCB] without trapping any solvents or liquids under the cap [because that might cause a short when it's re-energized after cleaning].
.

TGCT #51

Thanks for the information. I am very new to all this.
I'm working on any Apple, iMac, iSight model mother board trying to change some capacitors.
This may be the wrong forum but have you or anyone else worked on these Apple board? Is there any wiggle room for installing 20mm capacitors instead of the shorter ones or will the longer ones make contact with anything that they shouldn't in the tight space?

TGCT #52

I haven't worked on Apple/MAC boards but I'm sure a few members have.
Toasty might be a good one to ask.
https://www.badcaps.net/forum/member...tposter&t=7036
I know he's at least worked on MAC PSU's and even if he hasn't worked on the mainboards he might know who has..

[Toasty]

Re: Apple iMac iSight Midplane Recap

@edbog

What model do you have and what is the date of manufacture?

You can go a bit taller, but you'll need to get the back off your unit and check the clearances.

Definitely can't go to a larger diameter in the bank of {depending on your unit} 14(10+4) or 16(10+4+2) - 1800uF@6.3v caps. But, there is perhaps 5mm of height clearance you can exploit.

For the 1000uF@16v bank of 5, you may be able to notch up to a larger diameter, as there is a few mm's of clearance between those.

These units have lousy cooling to begin with and run very hot (135-158°F). Anything that further restricts the airflow is going to impact the system performance and/or longevity.

Also, replace ALL of the (up to 24) 1800uF & (5) 1000uF caps. The other small vent caps I would also replace since you're there.

While you have it apart, crack open the PSU and have a look. If you have blown caps on the midplane (Apple's 'word' for motherboard... ), chances are the PSU has them also. You'll need a #10 Torx security bit to open it.

Toast

[edbog]

Re: Apple iMac iSight Midplane Recap

I have the iSight model which was manufactured during the end of 2005. It is the 3rd version and the last before the Intels came out. It is opened from the front. The earlier versions are opened from the back. I have one of those also and it is much easier to open and work on then the iSight model but that one is working fine. To get at the iSight model the front cover(bezel?) has to come off first and then remove the flat monitor and underneath is sitting all of the electronics covered partially with plastic film. The earlier models are opened up by taking the back off. There are three boards in the iSight. The larger midplane, an almost square smaller one whose connectors are very short and tightly packed with one large capacitor and some smaller ones which do not seem to have blown or bulging capacitors and which do not seem to have any deposit on them and a long narrow rectangular one covered in film which I cut open and the only capacitors I saw seem to be o.k. The midplane has two capacitors that may be defective, 1800mF, 6.3V. with slightly bulging heads and a third, 1500 one that seems to have something on top which I am not sure if it is significant but I'm going to try and change it anyway. It isn't a powder but I can scrape it off with my fingernail. For all I know it could be fine. Nothing else is bulging and nothing else seems burned out. So, I'm hoping the problem is caused by these two or three capacitors. I received Rubycon capacitors but the rubber plug is slightly extended out of the base and I wasn't sure whether this is a fault and that is why I submitted my question. I didn't realize when ordering but the 1800 ones are longer then what is on the board. That is why I'm asking whether this extra length will have any effect or else I will have to reorder and get the shorter size. It will just take more time that I can save.

[Toasty]

Re: Apple iMac iSight Midplane Recap

Replacing just the noticeably bad ones is not the correct procedure. As I said in my previous post, "...replace ALL of the (up to 24) 1800uF & (5) 1000uF caps."

If 1 is visibly bad in that group from the same manufacturer's series, all of them will eventually fail if they have not failed already. They are not good just because they haven't leaked. Many caps fail and never show any signs. Jim Warholic's site sells a complete recap kit for these units.

See PCBONEZ's post here for some pics of failed bungs.

Please post a pic of your unit and the midplane, indicating the failures, so I can better advise. This is a new type of unit for me, so your pictures will help.

Toast

[edbog]

Re: Apple iMac iSight Midplane Recap

I can e-mail pictures as an attachment but do not know how to transfer it in a response like this. Jim Warholic's kits are for earlier models and not for the iSight which is what I'm working on. The mother board/Midplane has a lot of very small connectors which are difficult to disconnect from the mother board. Some of them about a quarter inch wide. Already the temperature connection from the HD to the mother board has three very small connecitions separated-not broken but disconnected from the mother board. I hope I can reconnect them or I wil not be able to measure the temperature of the HD if it doesn't cause more complications. Then there is putting everything back together the right way. Changing all of the capacitors? That is the best way but it will be a big job for me and I do not have all of the capacitors. I will just have to change the three and hope it will work. After separating the capacitors, there is still some solder remaining the the holes. I have a very fine steel pick which I pole into the hole and heat it up with the iron hoping the heat gets transferred to the solder in the hole and then I try to push and twist the pick so it goes through. I did this with one of the capacitors and soldered it to the board. My soldering technique is not great because each capacitor lead has a small glob of solder but the leads are not shorted out. I hope everything is properly connected. I'm waiting for the other capacitors to be mailed to me by Chris at Bad Caps. Unfortunately, the capacitors sent initially were the correct values but too tall. I had to send them back and I am waiting for the shorter ones.
I have a very small diameter drill bit which I used in model making that I can use to drill out the solder-hopefully but I cannot find it. So that is that.
There are too many connections from the hardware to the mother board and I have to be very carefully when moving the board while working on it so I do not break any connections. Everything is very small and tight.
That's where I am now. So, if anyone can show me how I can add a photograph to my response here, i would greatly appreciate it. I can then show the mess of the inside of the computer and the capacitors that I think are at fault.

Thanks,

Ed. Bog.

[Toasty]

Re: Apple iMac iSight Midplane Recap

A small favor please. Break your posts up into paragraphs when you post. It is very hard to read or find something when it is all run together.

Posting Pictures: Use the 'Post Reply' button under the last post or choose the 'Go Advanced' button under the 'Quick Reply' space. Once there, use the 'Manage Attachments' feature under the 'Additional Options' section to upload your pics. You'll click the 'Browse' button and go find the pic file on your computer and select it. Choose any other ones you want then click on the 'Upload' button to transfer them from your computer to the BC Forums server. Once that is done, click the 'Close this Window' button. Your pics will appear once you click 'Submit Reply'.

There are Recapping Tutorials on the badcaps.net home page. Look down the left side and choose which one you'd like to review.

Practice soldering & desoldering. Find any junk electronics device on trash night and take it apart and practice on it. You can refine your technique in a night or two of practice and feel more confident working on the mainboard.

Toast