Slot-loading DV Display/HardDrive seize up

Question

I am posting a conversation I have been having with a discussion board user, as I think it will be useful for others
On Fri, Feb 18, 2011 at 4:46 PM, <**@**.com> wrote:
Hi Richard:
I've just been reading an exchange you had with someone named Graham in the UK about his iMac going black and becoming unresponsive. After a series of exchanges, you finished up (I think) with:
That can be a possibility. If it was the CPU temp that's causing this the entire logic board would have to have come loose or perhaps the conductive paste has dried out/failed, unlikely.
So upshot. In my experience the part that fails in these G3 iMacs is the PAV (The board you see when you look down from the top it's under the CRT and drives the monitor section. The logic board derives power from the PAV via down converter).
The shutting down is a classic symptom and the most irritating.
Others: No start - power light blinks or turns amber, video gets wonky - color shifts or size variations, sparks arcing sound, native screen is dark but external monitor works fine (not on option on your 350, no external spigot). This is why I've got 7 or so iMac G3s in my basement. Mostly 350s since I was given around 20 of them and I repaired and donated most into the inner city. The ones left have PAV problems.
Wacky upgrade options:
I'm especially interested because here you mentioned the other main symptom I've noticed in my own version of the same problem: the "arcing sound" which I've been hearing almost from the start of my issues. Everything else almost mirrors his, except the time for the symptoms to kick in has reduced to less than 10 minutes.
I thought it might be the drive, so I've tried 2 different hd's, and it happens with both, and I tried running the iMac (400jhz slot loading) just off of CD, and it shut down then too!
Obviously, I've been inside the machine to replace the drives, with my teenage daughter's help (my eyes aren't so hot). I'm going to check for this OS X temperature software and see what it tells me. I did run a RAM checker, and it said it was all fine, so at least I know it's not that. I tried to get a version of Apple Hardware Checker for it (or whatever it's called) but it said the iMac DV would not run the software.
Do you still have those . . . PVA's? This machine is a perfect print server and backup hd and work stereo, and we have enjoyed tinkering with her in the past. If it wasn't TOO complex, I'd like to give it a try. I showed my daughter how to solder a battery cable onto a tester circuit board, so if that's the kind of thing we'd need to do, I'm game.
Let me know, and I'm looking for a temperature checker right now. Oh yea, and Tricia Helfer DOES look pretty hot.
Carey
On 18-Feb-11, at 8:37 PM, spudnuty wrote:
Hi Cary,
the other main symptom I've noticed in my own version of the same problem: the "arcing sound" which I've been hearing almost from the start of my issues.
That arcing sound is almost always the flyback transformer. That is on the PAV board which is basically the entire upper half of the computer. Here's a site in England where you can download the Service Manual for your machine.
http://www.macmanuals.co.uk/
So since you have a 400 MHz machine it's one of the more desirable machines since it has firewire. 400 to 700 had them. As I mentioned in my post I would pull the logic board and transfer it to a working 350. If you look in the manual swapping the board is simple. Then again around Chicago these G3 iMacs are sold for $25 or less. Don't know the situation where you are.
I used to repair these but they've become so cheap that the board swap is now my chosen path.
Richard
On Sat, Feb 19, 2011 at 12:22 PM, <**@**.com> wrote:
Richard:
I guess this shhould've been on the discussion board so others could see it, but I'll just ask one more thing before looking into the manual:
Remember, I've swapped a harddrive and memory, but board changing is something I've never tried before:
So, are you saying that the PAv that might be creating these issues, being such a large part of the computer, should just be abandoned, and the logic board swapped into a 350 because of it's simplicity? Does the logic board contain the 400 mhz processor and firewire hookup, or would those be left behind on the 400 iMac's PAV board?
I'm looking at the manual, and you're right, pulling the logic board does look pretty simple, but I haven't found the answer to the above question yet, so I'll send it to you.
I emailed this to you because the original post a over a year old, and I wasn't sure you'd still be watching the discussion boards. Next time, I'll just 'trust to the boards', though I've only received 2/5 answers through it over the years.
Thanks again.
Carey
On 19-Feb-11, at 6:17 PM, spudnuty wrote:
Carey,
So look at the pic I enclose. It's from the service manual.
So you've had the machine apart to this point, from here it's just the removal of the 10 screws to remove the logic board and down converter. They plug into the upper part via a couple of connectors. There could be a few plastic rivets that tie the board to the divider panel.
Does the logic board contain the 400 mhz processor and firewire hookup, or would those be left behind on the 400 iMac's PAV board?
That's all on the logic board.
Basically the iMac is a CRT display and speakers with a logic board underneath with the optical drive and the hard drive.
The board on top is called the PAV board ( power analog video) i. e. video power supply for a computer monitor. Power comes from that board and comes down to the "down converter" which changes it to logic board power, basically 12V and 5.5V DC. (These boards have been run "headless" but now not worth the trouble)
So your path from here will be determined by what kind of donor iMac you find. It must be a slot loader and the chances are it will be as fast or faster as your current machine.
Richard
On Mon, Feb 21, 2011 at 11:17 PM, <**@**.com> wrote:
Hi Richard:
Well, despite your own circumstances with blueberries and strawberries falling from the computer sky, I've gone on 4 different user forums and several different 'used things for sale' websites, and so far the closest I can come to getting a used imac is having one shipped from the next province (about 500 miles) for about 50-60 bucks, or possibly one in the city which the poster said they wanted 200 bucks for. I've had no reply to my email to them, yet.
Would you be willing to sell me one of those PAV boards, if they're still kicking around? I would think the shipping would be much less than the whole darned computer.
If you don't still have them in piles around you, I may just have to turf the iMac entirely for budgetary reasons.
I guess with the much smaller population, the proliferation of iMacs is similarly reduced. There's only about 3 million people in Alberta, which is where I am.
Let me know.
Greatly appreciate the information connections you've made for me.
Cheers
Carey
On 22-Feb-11, at 1:17 AM, spudnuty wrote:
Hey Carey,
Well I was forced to leave all of my iMac G3 parts with a recycler in Chicago when I moved.
I actually found one here in Pocatello (town of 60K) for $25 so maybe you can find the same thing. I don't have a PAV board and they are very hard to swap out, don't think I ever did it.
So, thinking a bit more about your situation, since you're using it as a server, when it fails does it absolutely freeze up? On the 400 you can attach a VGA monitor to the spigot under the perferated oval grill under the bottom rear. The monitors can fail in these and still produce power to run the logic board. Around here you can get a cheap LCD 15" monitor for around $25. A CRT type you can probably get for free. So if you're lucky it can still work that way.
There were people who ran a logic board headless, but most of these are out of date:
Here's a few:
http://www.applefritter.com/node/2241
http://www.cryogenius.com/hardware/imac/
a translation of the classic French mod:
http://www.hardmac.com/articles/39/page1
Soo hopefully yours will fail and just the CRT will be involved.
Here's hoping...
Richard
<Edited by Host>

Answer 1

Perhaps one of your RAM modules has gone belly up. To test this, remove both RAM modules and start up. If the RAM is the cause of the problem, the computer will respond with a complaining chime, and of course go no further. But that will indicate the RAM is cause, and you can go to the next step; try to start up with just one of the RAM modules installed - either one. If that gets you nowhere, try the other one.
If the problem is not bad RAM, it is beyond my expertise to help. Sorry.