Need help with iMac Powersupply

is your power strip faulty/overloaded

what did you do to get it to make the noise?

The PRAM shouldn't cause this, but you might check the voltage anyway, as it's hitting the age of battery death. You might un plug it, push the PMU reset once, then let it sit for 10 secs before you plug the AC back in. That will let you test if it is just a bugged PMU. Also, look inside near the RAM slots, there is a small LED between them and the ports. If the systek is getting any 3.3v power after pressing power it will light up.

have you looked at the cable? i have one of those, and sometimes if the cable isnt just right in it, it wont boot, and if it does, i sometimes is easily shaken out of place.

i solved the problem by wrapping a pice of masking tape around the plug, but just enough to make it a snug fit. electrical tape works too.

John

PRAM battery was dead and I replaced it.

I reset the PMU and the LED does light up bright when I push the on button and than stays on (not as bright). It just gets the CRT sound but still doesn't finish starting up (hard drive, video etc).

I have the manual showing where to check for 5v trickle going to the logic board. I have tried to check it with my multimeter but I am not sure what to set on my meter. Anyone know? I used DCV 20 setting and I only got 4.6v never 5v.

this is the multimeter I am using:

Sounds just like the symptoms my iMac DV 400 has. I've deduced mine is not mobo or DCB related, but must be on the PAV. I'm thinking it could be the flyback, but I haven't had the cash or time to replace it.

I read your node and it is exactly the same symptoms. It problably is the PAV board. Since that is the hardest to remove, the largest board in the mac, and probably the most dangerous...figures!

But I can't be sure unless someone helps me with my question about setting my multimeter (see above).

So if someone out there knows multimeters and could post or PM me, I would be very appreciative. Right now it is sitting in a multitude of pieces because I don't know if my diagnostics are correct so far.

MaxTek

Using DCV 20 should let you do all the tests listed. If you are testing a negative voltage, your meter might support it and show a "-xx.xx", but if not you can swap the red and black probes on what you are testing and you'll get the reading as a positive voltage.

OK using "DCV 20" I got the readings as follows:

J9 Pin 1= 4.97

DCO C10= 0.00 computer off but plugged in

DCO C10= 0.00 computer on (at least the logic board LED is)

Black Connector J7
Pin 2= 11.87
Pin 4= 4.38
Pin 14= 1.90

PAV Board Fuse reads O

Anything jump out at you? As you can see from all my readings they are just short of the manual specs. Except the DCO C10 which is zero. I couldn't get anything there.

Help!

It's tricky if you've never done it before. From 2000-2004, I reached a point where I could do the repair without thinking. Now, it's been over a year since I've done one. Since slot load iMacs have taken a sharp hit in depreciation, I've taken the attitude of use it till it dies, then sell the good parts mentality. Though, a new analog board should run about $100ish. Just be careful with the flyback - the crt can crack very easily. (yes, I learned this the hard way) Trouble is that between the different variations of the slot load iMac, so did the PAV/analog board. (it's also tied to the vendor who made the crt - the LG electronics components have a higher failure rate) From Apple (or an Apple reseller), a new analog board is going to run about $250 or so before factoring in labor. You're best bet is through Southern Computer Repair (can't remember their web page, they are based out of Atlanta, GA) or PreOwned Electronics (preowned.com)

Thanks for info but you didn't say if you think it IS the PAV board from my meter readings.

IF it is the PAV board I will trash it and use the parts elsewhere.

I'm guessing you just did the full board swaps only? I'm interested in trying an actual repair to the board to solve the issue. It sure seems like a flyback might be the cause, but I don't know enough of the electronics to follow the circuit intertwinings and what makes what else fail. I'd sure jump at a $30 part + labor to fix it over a $100+shipping+labor to replace the PAV.

I assume you did an open firmware reset.to rule that out.
otherwise look here...
>http://www.macopz.com/columns/imacrepair/

How do I do that when its dead in the water (except for the pretty green LED on the logicboard).

Unless your talking about resetting the PMU, which I have tried and nothing.

As for the link you supplied, I have seen that when I was searching for info on a dead Bondi. But my post is about a Graphite 600mhz and mainly trying to learn how to pin point which part is bad. The down converter, the logic board or the P.A.V. board.

As with maxTek, the iMac won't even try to boot, let alone get anywhere near to letting me into OF.

Another thread I jsut Googled is on MaNN Forums. It covers both tray and slot loaders. It does seem to be the flyback, but there is a lack of slot info until the latter part, and not many repair reports.

Well it appears since none of us can come up with a definitive answer that this pristine Graphite iMac is going to be parted out.

Will the 600mhz logicboard (and CDRW) work in my iMac DV 400mhz?

MaxTek

Yep. I've had the 400 DV mobo in my 350. I'm guessing that you've got updated firmware in the 400? The update affeccts settings on the PAV, so you'll want to check and update the 600 if need be right after you put it in. Otherwise you might get the no video problem.

I got two iMacs that did the same thing. Replacing the PRAM battery did not help so I searched the net for info on how to revive it.
On this page I talk about it and have links to the sites that helped.
http://www.applefritter.com/node/9274