Btw my G5 will not start or do anything short of lighting 1 led.

⟐ Commented April 19, 2013 at 9:26 pm -0700

Update

Hey guys, sorry it took so ling to answer back. I finally got a hold of a 10.5 dvd. No issues with date/time of fan spinning up like crazy. So that's what my problem was the whole time was wrong OS. Thanks again for the help :)

⟐ Answer accepted April 2, 2013 at 12:20 pm -0700

⟐ Commented March 24, 2013 at 5:22 pm -0700

⟐ Edited January 26, 2013 at 2:45 pm -0700

Can you give me any advice on how to get it started? Also I do not have a boot disk. Can I load it down? OS 10.4.11.

Then how do I get it started from there?

Thanks

Grant Lyon

⟐ Answer accepted January 3, 2013 at 4:59 pm -0700

What can i do?

⟐ Answered December 20, 2012 at 3:15 pm -0700

Is it possible to upgrade the 1.8 logic board with the 2.0 logic board and upgrade to the 2.0 power supply in an iMac that originally was a 1.8 ghz?

⟐ Answered November 29, 2012 at 2:04 pm -0700

Is there a good reference for Apple POST tests and indicators? book or website.

Thanks everyone.

⟐ Commented November 8, 2012 at 9:38 am -0700

⟐ Answered November 5, 2012 at 7:07 pm -0700

thanks very much.

⟐ Answered October 12, 2012 at 8:26 am -0700

The first two diagnostic LED light are lit. 3 & 4 stay off.

I can see no bulging or leaking capacitors.

Any ideas would be grateful.

Many thanks in advance,

Lewis.

⟐ Answered October 11, 2012 at 5:41 pm -0700

⟐ Answer edited September 4, 2012 at 5:51 pm -0700

1. would a non als specific powersupply prevent the imac from booting (I have not installed osx yet) 2. does a dim screen indicate at this moment a bad lcd, or 3. would bad caps on the motherboard prevent the imac from even lighting up the screen. Thanks in advance, I am pulling out my hair!

⟐ Answered August 12, 2012 at 1:47 pm -0700

- The LED 1 light is constant on.

- The power supply has no blown or buldging caps

- The Logic Board does not have any blown or buldging caps.

- I have switched out the RAM stick and it is not the ram.

what is another area to look? I don't have any other G5's to test against.

⟐ Answered July 29, 2012 at 3:50 pm -0700

When i power on i can hear the chime and then I can see noise on the black screen right before the white screen that has the loading icon on it. They are tiny multicolored specks that from afar look like vertical lines.

After this happens then the machine has a hard time booting. Sometimes it boots sometimes it doesn't. When I boot in safe mode it works every time and then occasionally I will see the noise while i am already logged on. When i boot in normal mode it will sometimes go to a black screen at the beginning of the boot and then the fans turn on at full blast "vacuum cleaner mode" i believe is what some of you guys call it.

I have searched everywhere for a solution and to pin point the problem. I have inspected the capacitors on the Logic Board and they are fine, not bulging or leaking. i have inspected the caps on the power supply and they are fine except that I missed the ones under the wiring harness. I will check on those asap.

Whenever I see someone with the same symptoms they almost always get the same response: Bad caps, bad power supply, bad logic board. I think it is the logic board but my question is: If in fact it is the logic board causing the problems, would the GPU be the cause of the problem? Has anyone tried to fix/ reflow these graphics chips?

I have seen it done on iBooks and laptops so I am wondering if anyone has tried it on iMacs. I have fixed many Xbox 360's this way and i have all the tools needed, but before I try it i want to make sure that a bad GPU would cause these symptoms and not some other part of the logic board. I would hate to buy a complete new logic board when all this one needs is a quick reflow.

⟐ Answer deleted June 30, 2012 at 8:40 am -0700

has developed a flickering over the whole screen area and jumps, i noticed few months ago that the 3rd of the screen from the top had a noticeable lower luminosity/brightness [like milky greenish]

Q. Re these related or am i looking at a combination of issues,

I have using you tube information inspected the main boards psu logic and cables but couldn't see anything obvious. However i had to clean the fans from clogging fluff and dirt, there seem to be some improvement with the flickering but now its back again, the start-up colors are also naff as it is pink then gradually improves to white.

I have also reseated connectors as a backup.

does anyone have any ideas on this?

ta! chris

⟐ Commented May 20, 2012 at 4:53 am -0700

⟐ Answer accepted May 13, 2012 at 7:09 pm -0700

Any suggestions?

Could it be something other than my hard drive that was dying? Ram?

Thanks for any help!

⟐ Commented May 4, 2012 at 3:13 pm -0700

⟐ Answered May 2, 2012 at 12:07 pm -0700

I tried using the diagnostic CD but it won't run, also tried to boot using system installation CD to run disk utility but still it won't boot. The last thing I did is to open the iMac and found out that it has 3-5 capacitor that popped. Maybe this is the problem and I want to replace them.

⟐ Answered April 26, 2012 at 7:24 pm -0700

⟐ Answered April 1, 2012 at 3:59 pm -0700

I need to remove 2 screws on logic board connector...I believe it is a small phillips...7.3mm...where can I find the screwdriver to do this?

⟐ Commented March 27, 2012 at 8:11 pm -0700

I have an imac with a strange problem. The machine does not seem to have any compactor problem, but the second diagnostic led is blinking. The first one is steady on and even without pressing the power button the second led blinks. As I have read the second led should be turned on when i turn on the machine, but it blinks when I connect the power cord.

I disconnected the power button cable and does the same thing. Also I reset the PMU. Also I tried an other power supply from a friends computer, just to be sure.

Do I need a new logic board??? Can I see anything else before trash it???

⟐ Edited March 20, 2012 at 1:58 pm -0700

⟐ Answer edited March 10, 2012 at 8:25 pm -0700

So basically what happens is when I turn on the iMac, as soon as it starts loading the system it will turn itself off after a flurry of white noise on the screen.

Subsequent boot attempts bring it gradually closer to a full boot, until it completes after about the 5th attempt.

This seems to be video card related. When it's booted up, there are graphics glitches on the screen; doing something video card intensive causes more glitches, and starting the screen saver causes it to shut itself off.

However, after about 15 minutes of being turned on... everything gradually turns to normal. The machine itself works perfectly after that! I don't see glitches anymore, I can use graphically intensive apps.

So this is an extremely weird problem. It's almost like it needs to warm up for a while first. Of course, that can't be it.

It must somehow be tied to the video card. Also, when I hold down the option key during startup (this brings up the "choose startup disk" screen), I can keep the machine turned on for as long as necessary without it crashing (presumably it doesn't yet use the video card at that point). So if I hold down the option key and keep it on that screen for a while, and then boot, it completes the boot in one cycle.

It would be great if someone could shed some light on this!

⟐ Answer accepted February 26, 2012 at 9:07 pm -0700

⟐ Answer accepted February 20, 2012 at 9:34 pm -0700

Should I still suspect a bad logic board???

⟐ Commented February 1, 2012 at 5:45 pm -0700

But it did not remedy the problem.

I have to wait approx. 8 min. until I can reboot the machine.

After that the machine runs perfect for another sequence.

Can you give me a hint?

⟐ Answer accepted January 29, 2012 at 4:34 am -0700

basically the title says it all:

I have a iMac G5 20" (2Ghz, 500GB, 512MB) which is working fine except for the screen being black. I know the backlight is working (and responding to dimming), so according to the apple guide (http://support.apple.com/kb/TS2094) it should be the LCD, but even with a replacement screen the display remains black.

What I've done so far:

- attached external screen - working

- tried another internal screen

- replaced display connecor cable

- checked capacitors - looking ok

I've run out of options to eliminate...

Anyone got an idea?

Update

The screen's Model ist LM201W01 A5 K3, the replacement screen was the same. It might have been K2, but the behaviour was 100% the same: LED3 on, backlight on, pixels black.

The LVDS socket looks normal, all pins visible and undamaged.

⟐ Answer deleted January 22, 2012 at 3:28 am -0700

⟐ Commented January 17, 2012 at 1:37 pm -0700

i have an iMac G5 20"A1145 (isight model) with a display problem. can i replace the faulty display with the one from an iMac G5 20" Model A1076 ( which has a power supply problem?

thanks

⟐ Answered January 11, 2012 at 3:20 pm -0700

⟐ Answered January 5, 2012 at 11:49 pm -0700

I am quiete sure that my old iMac G5 20” (modele A1076) is dead.

Is there a way to find another (new or working second hand) ?

because the power supply is move a bit I think...

or is there some easy small fix to do to repair it for a newbie like me? something like cleaning the screw removing re-putting...etc ?

Thanks in advance for any help.

⟐ Answer accepted January 3, 2012 at 11:07 am -0700

⟐ Answered December 22, 2011 at 10:03 am -0700

It was having general instability problems so I tried putting a clean reinstall of the OS, but the process failed, three times in a row. So I ran the AHT disk which came with the machine, and it quickly failed the short test with the following error code:

2I2C/1/1:0x00000092

Sounds like it could be related to the I2C bus to me. However, the I2C system is mainly diagnostic and reporting in nature. It reports actual voltage levels on the ram cards and PCI slots, stuff like that. So possibly, this error may not be the real problem.

I took the machine in to an Apple store and one of the techs noticed and showed me there was a bulging capacitor. Since they can only replace the whole board and send the old one back for remanufacturing (expensive), I wanted to try to fix it myself.

After reading about the capacitor/power supply problems I got a new power supply and worked on identifying the capacitor and finding its specks. I learned that beyond the capacitive value, voltage, and temperature ratings; that there are three related charateristics which seem to be critical to the power filtering role these capacitors play in this machine. (impedance or Z)^2 = (equivalent resistance or ESR)^2 + (capacitive reactance or X)^2 If you know two of them you can compute the third. Typically ESR is small and Z ~= X.

So why is this relevant? Well, the original capacitors are Chemi-Con KZJ Ultra Low impedance line with a Z = 12.5 m Ohms @ 100 kHz, unfortunately, this line was discontinued. Chemi-Con current offerings have impedances which range from 22 m Ohm to 49 m Ohm. Nowhere near the original spec. Worse, Digi-Key and Mouser don't carry the better lines, not even in a quantity of one! So I ordered the best available. When it arrived, I removed the bulging capacitor and soldered the new one into place. I also swapped out the power supply. Restarted the machine and... exactly the same problem as before. It still doesn't pass AHT, same error message.

So, does anyone on here have some advice on what I should try next?

Sorry about the long explanation, but hopefully it explains why I'm finding the whole thing puzzling. Why does Chemi-Con no longer manufacture capacitors with such low impedance any more? Why doesn't DigiKey carry what they do offer?

⟐ Answered December 21, 2011 at 1:43 pm -0700

By the way, there are no bulging caps on the logic board. I suspect a bad PSU.

⟐ Answered December 14, 2011 at 10:22 am -0700

is there any chance to find a new one ?

the old one is dead - it gets hot after the iMac is switched on - the iMac wont start, some times it shows the red led - sometimes it switches immediately off.

after that, i startet searching on the logic board and burned my finger tip on this part

⟐ Answer accepted November 15, 2011 at 12:45 am -0700

⟐ Comment deleted November 10, 2011 at 9:15 am -0700

⟐ Comment deleted November 10, 2011 at 9:15 am -0700

Update

As I bought this at a sale I followed your advice on how to open the unit to look for swollen caps,then i notice no hard drive or memory

were installed...can't afford to buy new so will try e-bay or Craig

and will follow your advice on how to install. Being 71 it won't be easy. Thanks Bill Lewes,DE

⟐ Commented September 28, 2011 at 9:18 am -0700

As the iMac functions better (& boots properly) the longer it's been off, but plugged in, is it possible the PRAM battery is the culprit? It's just beyond its rated life, and never been tested. Motherboard is not worth replacing for such an old PPC iMac. But if battery has any data flowing through it with any regularity, and not just on the end of a string such as an external drive, is it possible replacing this $3 part (plus installation, as I'm not comfortable with working on tightly compacted iMacs) and maybe not the expensive logic board, might fix it? Intuitively to me at least, as it will boot and run longer the longer it's been idle, it seems like more like a recharge situation than overheating or similar issue.

Any thoughts? Is my theory possible, if not likely?

⟐ Commented September 21, 2011 at 11:52 pm -0700

Thanks............L

⟐ Answered September 17, 2011 at 10:43 am -0700

For further info from me - Joe @ Pismo500@gmail.com

⟐ Commented September 16, 2011 at 9:01 am -0700

I got a restore disk, but it was the wrong rev. I think the machine told me what the correct rev was. But I can't get back to that point. How do you Boot the OS from the CD drive?

⟐ Commented August 20, 2011 at 12:06 pm -0700

http://s693.photobucket.com/albums/vv298...

⟐ Commented August 12, 2011 at 12:20 pm -0700

⟐ Answered August 12, 2011 at 12:14 pm -0700

I did all the replacement seemingly well, everything looks as it did before.

But when I turned it on, it turned off again instantly. So I went back and did the LED tests (first the second light didn't come on at all, and I thought that I had somehow killed the logic board) but then it just does the coming on half a second and going off.

This is a "brand new" refurbished power supply, any ideas?

Thanks,

Norbi

⟐ Answered August 12, 2011 at 11:43 am -0700

power up?

⟐ Commented July 19, 2011 at 7:25 am -0700

When I was looking on Amazon for a new one (since I'm not living in the USA) I stumbled upon an Airport Extreme card which supports n-draft. Since the old b/g-cards aren't that fast I was wondering, if I could just install this n-draft card and enjoy my nice 300mbit network with my iMac.

Is this card compatible with this iMac?

⟐ Answer edited June 10, 2011 at 3:10 pm -0700

⟐ Commented June 10, 2011 at 8:51 am -0700