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**PCBONEZ** · 02-16-2009, 03:19 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Okay, we'll come here then.

It will start to make more sense when you open the data tables in the links at mouser/digikey and compare the caps by their ESR and Ripple ratings.

Lower ESR is better
ESR can be thought of as how much 'resistance' the cap has to passing Ripple. [to ground in a filter circuit]

Higher Ripple is better.
The Ripple rating is how much Ripple it can pass without overheating.

Terms like "Low ESR" "Very Low ESR" "Ultra Low ESR" are -marketing terms-.
They have no 'official' technical definitions and so are used rather loosely.
One manufacturers "Very Low" may be another's "Ultra Low" and yet another's "Low".

What you should do is look-up the ESR/Ripple of the old caps and try to meet or beat those specs.

.

**Toasty** · 02-16-2009, 04:00 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

...finds two 50 penny nails....
WHACK! WHACK! WHACK!!
Now. Dang thread! Stay put dammit!

See post in: PRIOR THREAD

Good. Glad that the thread makes sense now.

Toast

Can someone lock the other thread?

**PCBONEZ** · 02-16-2009, 04:51 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

I found his old thread and posted there right when he was opening a new thread here.
Seems he had the same question two+ years ago and it never really got answered.

**ran** · 02-16-2009, 05:39 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Originally posted by PCBONEZ

I found his old thread and posted there right when he was opening a new thread here.
Seems he had the same question two+ years ago and it never really got answered.

Well,

First, I started this new thread because it was recommended I not "hijack" someone else's thread (e.g.nwd's thread about his Imac G5)

Second, that thread from a couple of years ago was for my old G4 Snakebite - i just went with the Nichicon caps from Mouser (Low impedance) and they seem to be working fine for over a year now......

Third, this thread does somewhat revisit that notion regarding all the different types.

I did wind up downloading the pdf datasheets, and find references to high life, high ripple, etc.... but just really wasn't sure what were the most important qualities for power supply caps, so just wanted some advice before I order.

Thanks,

Ran

**Toasty** · 02-16-2009, 06:30 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Originally posted by PCBONEZ

...he had the same question two+ years ago and it never really got answered.

Perhaps now it will be answered, or has it already, Ran?

I never used the word hijack!

I simply suggested that a new thread would get a better response, and it did! As soon as you started the new thread you had, what, 4 responses within an hour and a half?

Now, some nice pics of your leaky caps and the PSU would be nice. I think PCBONEZ has a photo collection going. ESPECIALLY Fuhjyyu! They're kinda like the Krispy Kreme Girls, you don't wanna look, but you're gonna!

Is there anything, besides the caps, that looks burnt or damaged in the PSU? A good pic of an undamaged coil we have discussed in the other thread would be appreciated. Some size reference always helps.

Toast

**Krankshaft** · 02-16-2009, 10:33 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Originally posted by Toasty

Now, some nice pics of your leaky caps and the PSU would be nice. I think PCBONEZ has a photo collection going. ESPECIALLY Fuhjyyu! They're kinda like the Krispy Kreme Girls, you don't wanna look, but you're gonna!

Toast

Oh man that's scorched into my retinas.

Here is a repost of my response from the other thread:

Yeah those aren't series numbers they are series manufacturer part numbers.

They correlate with the series, size, lead spacing, capacitance, and voltage.

They are great when you have to reorder a specific size and series of cap though.

You want to find a low ESR series for the cap company you are looking for and filter your search by series. Then look up the datasheet for that series to see the sizes available a link is usually available on the parts page. Those numbers will also let you know which size cap you are ordering since multiple sizes may turn up for a certain voltage and capacitance.

I use a digital caliper to measure the caps I'm replacing if space is tight. You will eventually get accustomed to the design of your cap companies datasheets I am very familiar with Chemicon's and Panasonic's my big two cap companies I use.

Funny you mentioned Nichicon VZ series I just bought one a 4700 uf at 63V for my new Mastech linear PSU to replace a counterfeit Chemicon. Luckily it's a linear so GP will do. Digikey was out of the Pana TS-HAs so size wise they were all I could get.

**Toasty** · 02-24-2009, 07:20 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Any word there, Ran? Never heard back on my questions from 2 posts back....?

**ran** · 02-25-2009, 09:36 AM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Originally posted by Toasty

Any word there, Ran? Never heard back on my questions from 2 posts back....?

Hi Toasty - sry not to respond earlier - In the midst of dealing with health issues with my dad and starting a new job...well, as you can guess there's a disassembled PS and a Mouser box full of shiny new capacitors sitting on my workbench.......and how long they'll be there is the mystery!

I hope to get to in within the next couple of weeks....... I...hope.....

**Toasty** · 02-25-2009, 12:07 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Hope all goes well for you & your Dad.

Good to see you're keeping busy.

Look forward to hearing about the fixup.

**ran** · 05-14-2009, 08:33 AM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Success!

This past weekend, I was able to disassemble the PS and I pulled out all the low-voltage caps.

A bit of a pain - with all the glue and especially the cap under the copper heatsink, but I finally got them all out.

Putting the new ones in was a breeze, just took my time. The only one that was a problem was the 10mm x 30mm 3300uF cap - I couldn't find a replacement of the exact size (resister right next to it), so just uses a 12mm x 20mm Nichicon replacement and situated it right above a small resistor before soldering into place.

Re-assembled, prayed, connected the PS, got the 1st LED diagnostic - goody!

Pressed the power button...nothing. Uh-oh. In fact, when the unit was dead, I still had gotten the 1st LED lit... just nothing else.

Reset the SMU, pressed the power button..... and voila! powered right up! Woohooo!

Been running it all week - and is working flawlessly.

I honestly thought, due to the 1st LED on the MB lighting up even when it was 'broke', that the PS was in fact ok and it was the MB that was dead...but I was, thank God!, wrong. MB is just fine.

So, my 2nd Mac requiring PS repair is now a success! (My first, the G4 SnakeBite referenced in an earlier post here on BadCaps, has been running solid for over 2 years now!!).

What's next, you may ask? Well, funny you should ask, but I have a Dual mirror-drive G4 PowerMac with a blown PS as well. Every time I put a new fuse in, it just pops and gives a little light flash. Now to open that one up and see what's going on.....

Also, for those looking for help, I came across Jim Warholic's pages with excellent information on the PS/MB problems with these IMAC's - here

Thanks for all your help everyone, this has been an invaluable resource.

**PCBONEZ** · 05-14-2009, 03:34 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Good Job!

**Toasty** · 05-14-2009, 09:42 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Superior! ( and about time!

) Hope all is well.

Fortunately yours was a "simple" recap and back to running. I now have 3 here that were/are not that simple and another thread has many (~10) that have not responded to the recap. The fight continues.

BTW - Warholic's site was also mentioned in nwd's PSU thread. Very informative, but not comprehensive enough for me. Several questions were raised by others but he never answered them.

Congrats!
Toast

**nanchatte** · 05-24-2009, 06:36 AM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Guys and gals, this is my fist post on this forum after skulking around trying to decide whether it was worth it fixing my 17" A-rev PSU.

I read a lot about fixing iMac 17" (rev A) PSUs on various Japanese boards (I live in Japan) and thought why not give it a go on an old iMac (currently an Objet d'art) that a mate of mine had lying around for a year or two.

I had the "one light only" symptom, after a couple of weeks of intermittent start up failures (no response to power button).
So I was sure my PSU would be fixable.

I nipped off to Akihabara and picked up some nichicons:

Here's a hand drawn schematic I found on a japanese website - and the damage shown matched that in my PSU exactly.

At first, I got to work on the caps near the larger toroid (A, B, C and D).
B, which had leaked badly by the looks of things, had scorched the top of the cover. C appeared to be on the point of rupture. TBH, I was amazed the thing had switched on at all!

To test my work so far, I plugged her back in and the machine started up immediately!

Yeehah. An hour later and she was humming along, just like before the failures.

Shutting her down once more, I decided to head for the home straight: I pulled the supply out and got to work on E, G and H which were relatively easy to reach after the previous four.

Fifteen mins later my job was done.

I plugged her in and.... Zero, zilch, nyet, nicht, nein, nada, nill, nanimo, buzai, nothing!

No lights, not even the first one I had originally.

And everything was going so well.

I only hope that I the damaged the motherboard.

My concern is that a residual charge may have damaged the PSU when I was soldering, because at one point, looking back on the repair, I remember feeling the soldering iron momentarily stick to solder, like it does after a small spark, locally melting the tin and effectively welding the bit to track before it has had time to heat up from conduction.

I guess I failed the first rule of working with capacitors which is to always LTFTD (Let the effing things discharge)!

I'm at a loss and am tempted to buy a refurb from YourMacStore, who will send an Apple refurb to Japan for a hefty 190!

Of course, the risk is that plugging the broken supply in to the motherboard has fried it and I'm wasting a further 200 dollars on a paperweight.

btw, the motherboard was replaced four months of light use before the PSU failure, so it currently has no issues, or even accumulated dust!

*sigh*

**ran** · 05-24-2009, 09:18 AM

Re: Imac G5 17" - no powerup (& bulging PS caps)

eek! That's a bummer.

Can you test the PS - e.g. do you have an ATX PS tester? That would be the simplest way of checking to ensure the PS is working.

I know on PC ATX supplies, you can short the PS_ON with a GRND pin on the connector to turn it on (with a load on it - fans, CDROMS, etc... connected).

I also have a special PS tester with all the connectors, but it doesn't work with these proprietary Apple PS's so I'm not sure how you'd do it with these PS's - I got the pinout diagram, but since I couldn't put a load on it, I didn't want to turn it on that way.

Anyway, I'm sure the guru's here could walk you through testing the PS.

A question - when you plugged the PS back into the MB, did you still see the first diagnostic LED come on? (referring to those 4 white LED's on the MB)

If so, have you tried resetting the SMU? That did the trick for me after my repairs...

**Toasty** · 05-24-2009, 10:05 AM

Re: Imac G5 17" - no powerup (& bulging PS caps)

What model number is your PSU? Apple P/N: xxx-xxxx

Did you try a system reset on the mobo. Others have had success with that.

Were the caps installed correctly polarity-wise? It happens to the best.

Have you jumpered the plug (not connected to mobo) to see if the PSU will start?

If indeed you had an undischarged cap, then you may have burned a trace on the board. Fortunately this board is not a multilayer and traces are only on top or bottom. Getting the gunk off the board to see the traces is necessary.

However, in the area where you were working in, those traces are substantial and I wouldn't expect a burned trace.

On the other hand, if it was not an undischarged cap, but rather the iron just sticking for a bit while the solder came up to temp, you may not have gotten solder to the other side of the board for one of those caps. Your iron wasn't hot enough or not enough time was allowed to get a good flow. Those caps legs pass current from one side to the other, so you may have a cold or no-solder joint right under one of the caps you lastly put in. This is especially possible on the ground traces which are large and sink a great deal of heat from the iron.

Another possibility is that replacing only some of these caps, is not a good idea. It may cause problems further along in the circuitry. Put F & I in and see.

E is the final 3.3 volt filter and is related to C
F is the 24 volt filter
G , H, & I are part of the 5.1 v standby

Good Hunting!
Toast

**nanchatte** · 05-26-2009, 07:01 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Toasty and Ran, THX for the quick replies.

Originally posted by Toasty

What model number is your PSU? Apple P/N: xxx-xxxx

it's a 661-3351 - Rev A.

Did you try a system reset on the mobo. Others have had success with that.

Yup, but NO DIAGNOSTIC LEDs were lit, so power's not even getting to the mobo.

Were the caps installed correctly polarity-wise? It happens to the best.

I've had explosive things happen to me when I've connected caps backwards after building a circuit with a hangover!

but there was silence... Nothing... no flames nor smoke.

I also compared the final with a photo I took of the original caps still in place to make sure :-|

Have you jumpered the plug (not connected to mobo) to see if the PSU will start?

How do you tell if the PSU is "starting"? I'm presuming that even under no load, there should be some voltage... or it wouldn't know whether it7s actually loaded or not! I need to find a Rev-A pinout. I've seen ALS pinouts but not Rev A pinouts.

I believe on the Apple PSUs you have to ground a different pin to an ATX supply, so I'm not sure how to proceed.

If indeed you had an undischarged cap, then you may have burned a trace on the board. Fortunately this board is not a multilayer and traces are only on top or bottom. Getting the gunk off the board to see the traces is necessary.

However, in the area where you were working in, those traces are substantial and I wouldn't expect a burned trace.

On the other hand, if it was not an undischarged cap, but rather the iron just sticking for a bit while the solder came up to temp, you may not have gotten solder to the other side of the board for one of those caps. Your iron wasn't hot enough or not enough time was allowed to get a good flow. Those caps legs pass current from one side to the other, so you may have a cold or no-solder joint right under one of the caps you lastly put in. This is especially possible on the ground traces which are large and sink a great deal of heat from the iron.

All good points.. yes, the tracks are a good 2mm thick. Vapourising one would have been a fireworks display.

No, I am 95% sure it was a discharge. I used to build high precision electronic measurement devices interfacing with NI LabVIEW boards for a living. As u can imagine, they had substantial filtering, including decent sized toroids and meaty caps.

I only ever experienced "sticky" bits once I'd tested the initial design in order to make some tweaks. It almost always required a replacement part once this had happened (it was also sometimes accompanied by a small spark). Usually an opamp or another IC would be blown due to discharge from the insufficiently drained caps.

(The components and finished products were paid for by the research centre, but time wasn't so I always tended to rush and have a bucket of spares handy 8-O. Of course, eventually I designed a load bypass as a way to rapidly drain the circuit but that's a different story.)

No, most likely I've killed once of the ICs. delicate little buggers they are.

Another possibility is that replacing only some of these caps, is not a good idea. It may cause problems further along in the circuitry. Put F & I in and see.

E is the final 3.3 volt filter and is related to C
F is the 24 volt filter
G , H, & I are part of the 5.1 v standby

Good Hunting!
Toast

Thx.

My plan of Action is as Ran suggested in a previous post, to get a Pinout. Figure out how to simulate a load and then test the voltages on the various pins. Once done, I can isolate the problem - or at least eliminate the working bits, if any remain!!!

But my gut instinct tells me its one of those surface mount jobs or at least a diode somewhere, since all the "analogue" bits are quite substantial.

Of course a schematic would be nice... or one of those Engineers' testing guides with test points and voltages (like the one I used to fix my digital Yamaha subwoofer) sigh... I sometimes miss well funded research centres with their attendant batteries of diagnostic tools! Heck, all I have now is a mediocre multimeter (try saying that after 3 beers!)

Cheers guys.

**Toasty** · 05-26-2009, 10:35 PM

Re: Imac G5 17" - no powerup (& bulging PS caps)

See uploaded image.

With unit plugged in and turned on (jumper):

1 : 2 : 12 = 3.3v

3 : 5 : 7 : 11 : 14 : 16 : 17 : 18 = ground/common

4 : 6 : 20 : 21 = 5.1v

8 = Power Good (5v)

9 = 5v StandBy

10 : 13 : 19 = 12v

15 = Power On (short to ground/common to run)

22 = 24v

Toast

H was relatively easy? That's the toughest cap to work on because of the heatsink..??

Are you sure you've the correct designations?

Attached Files

**ran** · 05-27-2009, 07:01 AM

Re: Imac G5 17" - no powerup (& bulging PS caps)

Here's the Apple PS pinout diagram I use (see attached pic).

It actually fits into my little ATX PS tester (round/square pin designations line up on the 20pin side (not 24pin) but I couldn't get it to power on so I didn't futz with it.

I'm not sure if this is true with these PS's , but I was always told it was bad to run PC PS's without a load, so with an ATX, I'd always hook up a few devices before powering it on to test the rails.

Would harm come to a PS with no load, such as if you were able to get this Apple PS going by shorting the on/off and GND?

Also, you say there are no diagnostic LED's. Just to clarify, when you hook it up to the MB and plug it in, you don't even get the first white LED on? That would be a bad sign.......

Attached Files

**Toasty** · 05-27-2009, 10:08 AM

Re: Imac G5 17" - no powerup (& bulging PS caps)

I think that the "no load" story is just that. Now, some PSU's won't start without a load, that much is true. I've never had any harm come to a unit with no load. The Apple ones all start without any load.

The ATX tester is just that, for ATX PSU's. Not Apple.

The "no LED" indicates that the 5.1vSB is missing, and that's some of the last caps he was working on.

The 2 chips nearby that are the LM393 dual comparator (8 pin) & the WT7515 protection circuit (14 pin) for 3.3v, 5v, 12v. The WT7515 is connected directly to the PG wire.

Toast

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