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View Full Version : Is my PowerMac G4 MDD....DEAD?!




MrCheeto
Aug 29, 2009, 07:39 PM
How can I tell what's wrong with this busted G4 I just bought? I assume it could be the easy to replace PSU, but I fear it could be the dreadful *gulp* FATHERBOARD!!!

When I press the power button, I get NOTHING! No beeps, no whirs, I don't see a fan stutter and the LED doesn't do a thing. :D

Also, how can I tell if it's dual or single CPU? It just says "1.25ghz" on the back label.



OrangeSVTguy
Aug 29, 2009, 07:58 PM
The PSU is more than likely shot. Good luck replacing it for under $100 :p. You can still sell your "dead" psu for a few bucks as people out there refurbish them. You can take it apart to see if it's just the fuse that's blown.

If it's a dual processor, it will say 1.25DP on the back label :p.

Good luck and let us know how everything works out.

MrCheeto
Aug 29, 2009, 08:05 PM
Thx

MrCheeto
Aug 30, 2009, 03:34 AM
Is there a way to test to see if it's the PSU besides getting a new one?

OrangeSVTguy
Aug 30, 2009, 07:06 AM
You can manually jumper the PSU(I think it was the green wire and any black wire) to turn it on and then with a current tester, you can check all the pins for correct voltages. Also if you jump the 2 wires(check to be sure) it should also turn the fans on so if that doens't work, then more than likely it's shot. Also take apart the PSU to check the fuse if it won't turn on.

Here's a link to the correct voltages, http://www.xlr8yourmac.com/tips/MDD_ps_mods/MDD_PS_Mods.html.

MrCheeto
Aug 30, 2009, 02:53 PM
ZOMG! I'ma gonna poop in my pants!

First off, the beginning.

5 months ago I bought 5 dells for $100. I cleaned them up, put XP on 'em and sold some. Some guy emailed me saying he needed help with his PMG4, I instead offered to trade a working Dell for his dead G4. He brought it over and we made a fair trade, I swapped the optical drives because he wanted to keep his DVD writer.

Investment: $25

So, I got to work diagnosing the problem. NO reaction to the power button being pressed, no fans, nothing...so that means...the power supply! $100? :(

But I got curious and cracked it open and saw a big tiny little huge fuse glaring at me! It was dark so I thought "BINGO! What a deal!" but turns out it was painted by the manufacturers that had placed it there, I dunno, to twist my leg or something. So then I went into a deep depression and even contemplated pesticide, but when I studied the fuse even closer...I realized...even though the center element was in tact one of the ENDS had blown!!!!


OH HAPPY DAY! $27 and I haz a working PowerMac!! Well not yet, I'm buying a fuse today but I WILL keep you updated!! ^.^

http://i189.photobucket.com/albums/z154/mrcheeto/th_DSC_1701.jpg (http://s189.photobucket.com/albums/z154/mrcheeto/?action=view&current=DSC_1701.jpg)

You can see a tiny bit of black paint on the right end, what kind of #$%& does that sort of thing?!

MrCheeto
Sep 3, 2009, 12:21 PM
Crap! I bought a fuse, put it in, and it burned right through it as soon as I connected power!

Come ON!

So this means it's shorting out somewhere, most people will tell me to buy a new one but I'm telling you I'll fix it! Just tell me how to find the culprit >8\

OrangeSVTguy
Sep 3, 2009, 01:16 PM
Lol. I had one of those problems with my MDD too. Took me 3 fuses before I realized it :D lol.

Check solder traces on the PCB board of the PSU. I heard/read that the solder actually melts causing a short since they get too hot. I never could find out what was wrong with mine so I just sold them on ebay for parts/repair, I believe I got $75+ for them.

MrCheeto
Sep 3, 2009, 01:20 PM
Crap, what are the odds of finding someone that would repair it/exchange it for a fair price?

As with any capacitors there's risk of lethal shock, how do I discharge this thing?

OrangeSVTguy
Sep 3, 2009, 01:37 PM
I believe you just let it sit for 24 hours unplugged.

nanofrog
Sep 3, 2009, 02:02 PM
Crap, what are the odds of finding someone that would repair it/exchange it for a fair price?[/QUOTE}
Check your local Phone Book and look for an electronics repair shop, if there's any available, and give them a call, and see what happens.

[QUOTE=MrCheeto;8413319]As with any capacitors there's risk of lethal shock, how do I discharge this thing?
Use a resistor, larger values would be best, as it's likely going to be a low power part (low values can blow due to higher current than part rating). It can take a while, but the safety is worth it.

Connect one end to each leg on the capacitor. CAREFULLY. An old heating element can work (particularly useful for large values of capacitance too, as it's going to be converted to heat and they're rated for high power). Check with a meter and see if it still retains voltage before attempting to handle it (contact with you), then you can desolder.

MrCheeto
Sep 3, 2009, 02:04 PM
Thanks!

I don't see ANY solder joints that look more melted than usual, lul, nor are any crossing.

Well, might as well start calling places. What's this "phone book" you speak of?

nanofrog
Sep 3, 2009, 02:19 PM
Thanks!

I don't see ANY solder joints that look more melted than usual, lul, nor are any crossing.

Well, might as well start calling places. What's this "phone book" you speak of?
You don't know what a phone book is?
Where are you located?

Odd, but OK. It's usually a book (thickness varies by location) that contains published telephone numbers for both local businesses and residential customers. Sometimes the business and residential sections are split into different volumes, but none the less, there's usually such a book(s).

Worst case, look it up online. It would serve the same purpose (same information, just online). Take a look at Yellowpages.com (http://www.yellowpages.com/), if you're in the US.

Hope this helps. :)

MrCheeto
Sep 3, 2009, 11:57 PM
Hey folky polks!

I've decided to check the capacitors, some seem dry. I'll post after checking/experimenting with them ^.^

MrCheeto
Sep 6, 2009, 03:16 AM
Update:

Um...how can I tell which are bad? If they wobble a little as I poke them does that mean something? I've got a multimeter, what can I do to help determine which parts need replacing?

leighonigar
Sep 6, 2009, 03:33 AM
If this was my computer, I would think about swapping the PSU for an ATX one.

http://www.applefritter.com/node/23857

http://jimmykirk.com/?p=34

etc

http://www.google.com/search?client=safari&rls=en&q=G4+mdd+ATX+psu&ie=UTF-8&oe=UTF-8

MrCheeto
Sep 6, 2009, 03:43 AM
Thanks buddy.

I've seen this but sadly I will lose the ability to plug in a ADC Apple Display :( I need that 25v pin ><

nanofrog
Sep 6, 2009, 12:25 PM
Update:

Um...how can I tell which are bad? If they wobble a little as I poke them does that mean something? I've got a multimeter, what can I do to help determine which parts need replacing?
Is there any brown/green-brown substance on the board (leaked fluid)?

Pics would help immensely.

BTW, have you been able to locate an electronics repair shop in your area?

MrCheeto
Sep 6, 2009, 12:43 PM
Well I've been looking for ANYONE that does board-level repairs. TV and guitar amp techs and the like. I'm trying every shop in the area.

Let me know what you want pics of. No, visually the board is pristine, I took a volt meter to the caps and all of them shoot up in resistance as if new. However the 420v cap has a TINY bulge in the top and stops at about 320uf. However the problem is somewhere the board is SHORTING, which wouldn't be caused by a cap not holding power.

http://i189.photobucket.com/albums/z154/mrcheeto/DSC_1661.jpghttp://i189.photobucket.com/albums/z154/mrcheeto/DSC_1661-1.jpg

nanofrog
Sep 6, 2009, 01:08 PM
Cheeto,

Caps can fail as a dead short. :eek: Leakage and bulging are big clues there.

A pic of the stuffed side of the caps (non soldered) might help (all if possible, but definitely the bulged part).

BTW, have you been at it with a soldering iron (first pic, left side)?
Looks like there's been some rework (appears as rosin flux residue at large "blobs" of solder on joints).

MrCheeto
Sep 6, 2009, 01:40 PM
"Caps can fail as a dead short." Ok, but when I take my multimeter to all the caps I don't get a short reading, it says Open...?

No I haven't touched it. I recently fixed another person's MDD and used their power supply to test my machine, works perfect. I opened their PSU and the bottom of the board appears completely similar, even the rosin on the leads was just as globby in that area. Both are the Samsung replacements =\

Caps cluster
http://i189.photobucket.com/albums/z154/mrcheeto/th_DSC_1661_2.jpg (http://s189.photobucket.com/albums/z154/mrcheeto/?action=view&current=DSC_1661_2.jpg)

http://i189.photobucket.com/albums/z154/mrcheeto/th_DSC_1662_2.jpg (http://s189.photobucket.com/albums/z154/mrcheeto/?action=view&current=DSC_1662_2.jpg)

Slightly bulged top
http://i189.photobucket.com/albums/z154/mrcheeto/th_DSC_1663-2.jpg (http://s189.photobucket.com/albums/z154/mrcheeto/?action=view&current=DSC_1663-2.jpg)

nanofrog
Sep 6, 2009, 07:42 PM
"Caps can fail as a dead short." Ok, but when I take my multimeter to all the caps I don't get a short reading, it says Open...?

No I haven't touched it. I recently fixed another person's MDD and used their power supply to test my machine, works perfect.
OK, so you know for sure the system itself is fine, and it's just the PSU. That helps, as you know once the PSU is sorted, you won't have any nasty surpises. :D

I went back up to the previous set of photos. On the second, I noticed something on the smallish daughter card. In the upper left, it appears there's some scorching on a surface mount resistor(?) next to a pair of through hole pins. Also, the line of surface mount components at the top right. I can't tell if that's just flux residue, or something else (due to over heating).

At this point, if you have the skills to dissasemble and test out each component, this would allow you to discover any dead part/s. But you might want to test out the daughter board first. If possible, your friends PSU could serve as a guide to detect what's good or bad. :)

Otherwise, find a shop that can, if at all possible. :(

MrCheeto
Sep 6, 2009, 08:12 PM
WOW! Good eye!

Sadly (this is sad...right?) the cap that appears blown works fine as I just tested with the multimeter :( I'm disappointed, I thought I was done searching.

Nice catch, thanks everyone. I'll try and nab me an unsuspecting nerd or something.

nanofrog
Sep 7, 2009, 01:15 AM
WOW! Good eye!

Sadly (this is sad...right?) the cap that appears blown works fine as I just tested with the multimeter :( I'm disappointed, I thought I was done searching.

Nice catch, thanks everyone. I'll try and nab me an unsuspecting nerd or something.
If you're attending a universtiy, make a friend in the electrical engineering dept. ;)

BTW, the bulge on the cap in question isn't bad, as many do bulge a small amount in high heat situations. Given the age of the PSU, it would be a good idea to go ahead and replace all the capacitors on it, as they do go bad over time. By 10 years, you should go ahead and replace them if it's an item you wish to keep working. ;)

Good luck. :)

SilverL
Sep 7, 2009, 09:30 AM
If you need a power supply for an MDD, I can send you one for the cost of shipping.
Saves me having to toss away a functioning PSU...

MrCheeto
Sep 9, 2009, 09:02 PM
Thanks folks for all the help!

I finally discovered it's the transformer (the big yellow laminated transformer, closer to the fuse in those pics) which means I'm kinda in for a hell of a hunt o.o

Crap, I hope we can either find an equivalent transformer or repair the one we have. It's dead-shorting.

Brien
Sep 9, 2009, 09:10 PM
Or buy the PSU off the buy who posted before you.

MrCheeto
Sep 9, 2009, 09:16 PM
LUL!

We'll see. All I need is a transformer the same size and rated to something close enough to work in it.

Let's not forget that these things are showing their age, so even if I bought other "working" ones online, they're days are numbered. By actually replacing the defective part on this board I'll likely extend the life greatly.

nanofrog
Sep 9, 2009, 10:35 PM
LUL!

We'll see. All I need is a transformer the same size and rated to something close enough to work in it.

Let's not forget that these things are showing their age, so even if I bought other "working" ones online, they're days are numbered. By actually replacing the defective part on this board I'll likely extend the life greatly.
Replace the transformer and all the capacitors. You should be good at that point. But if you leave the original caps, they will go on you, and sooner than later, given it's age.

As long as you can read the P/N's or values, you should be able to locate an equivalent part. Everything should be readily available. :)

Hope this helps. :)

MrCheeto
Sep 9, 2009, 10:38 PM
chaw bru!

I just hope I never smell the "sweet" smell of a diode cooking 0.o

nanofrog
Sep 9, 2009, 10:44 PM
chaw bru!

I just hope I never smell the "sweet" smell of a diode cooking 0.o
Try trannies. :p Very distinct odor. ;)

The worst I ever witnessed was ASIC explode! (Apple IIe's CPU btw).:eek: What a show. :p

BTW, do you know where to look for the parts you need?

MrCheeto
Sep 9, 2009, 10:46 PM
Hm, well the transformer in the power supply went, if that's what you mean, and I smell nuzzing, NUZZING! I guess it shorted and didn't actually splode like a death star?

Well I can find a load of caps at the RadioShack, the rest I'm lost on. =\

nanofrog
Sep 9, 2009, 10:59 PM
Hm, well the transformer in the power supply went, if that's what you mean, and I smell nuzzing, NUZZING! I guess it shorted and didn't actually splode like a death star?

Well I can find a load of caps at the RadioShack, the rest I'm lost on. =\
Yeah, you burnt the varnish off the windings. As it's old, the odor would be non existant.

BTW, have you made sure it didn't take anything else out with it?

As for getting parts, skip Radio Crap. They carry almost nothing these days, and aren't worth it. Junk parts, if they even have it. On the caps, make sure you use temp = 105C parts (noticed that off the photos). Anything else, you'd loose capacitance at best (high temp = reduced capacitance) or it could actually go DOA on you.

You'd need to order from:
Digikey (http://www.digikey.com/)
Mouser (http://www.mouser.com/)
Allied Electronics (http://www.alliedelec.com/)

MrCheeto
Sep 9, 2009, 11:01 PM
Darn, I always forget mouser ^.^ Danke!

nanofrog
Sep 9, 2009, 11:04 PM
Darn, I always forget mouser ^.^ Danke!
NP. :)

Didn't know if you knew of any of them, but they're listed in the order of my personal preference for prototyping components. ;) If you're interested in electronics, or better yet, taking EE or CE as a uni major, memorize these sources. :D :p

Mrburns
Sep 15, 2009, 12:34 PM
If you need a power supply for an MDD, I can send you one for the cost of shipping.
Saves me having to toss away a functioning PSU...

I could use that power supply if you are still willing to send it for the cost of shipping. Let me know . Thanks

Elgie
Sep 25, 2009, 10:44 AM
If you need a power supply for an MDD, I can send you one for the cost of shipping.
Saves me having to toss away a functioning PSU...

SilverL,

I will buy that PSU from you for a reasonable profit it you still have it and if it is functioning. Send me an email please or reply here if interested/still available. PayPal, check, whatever you prefer. My email address is, if you can't find it in my profile, no spaces or special chars: e j l o n l i n e @ y % a h o o . c o m^

Thanks,

Elgie

bokap
Oct 22, 2009, 02:59 PM
Does this sound like a bad power supply? I turn off when I go to bed, in the morning dead. I replaced the battery, reset cuda. If I unplug for about 10 minutes it will restart. I am worried that sometime it won't start so I leave on always.
Bob