iMac "iMac600" SE...

[iMac600]

...is knock, knock, knockin' on heavens door.

Since i've owned it, predating even my involvement on these forums, it's been a loveable old machine with CRT problems. The display flickered, brightened and dimmed constantly and would always shut down to the sound of thousands of electrons crackling away on the surface. Couple this with a few other issues, for example a punctured speaker cone, a dead optical drive, a hard disk that won't start up... this machine is shot to bits.

Time to let go. Time to move on.

Yeah, as if.

I'm currently awaiting the IT staff to return from leave (should be a couple of days, tops) so I can pick up some of their spares. Speakers, Hard Disk and Optical Drive are easy replacements. What i'm going for here is a complete overhaul of the G3's CRT assembly. What that essentially means is:

• The Logic Board, Optical Drive, Hard Disk, Drive Carrier, EM Shield and Speakers will be removed.
  
• The outer shell will be dismantled down to just the CRT and the face plate.
  
• The "divider plate" and G3 heatsink will be reused from the 600MHz G3 CRT assembly, as the 400MHz assembly fitted to the donor CRT is incompatible
  
• The system will be reassembled and calibrated for the replacement tube (depending on the make, either an LG or CPT CRT)

While the system is apart I will also explore the options for a 12v 10cm cooling fan to be added just above the neck of the CRT. This will aid in ventilation. Otherwise, i'll look into clearing restrictions in the air flow path for convection cooled systems.

I must reiterate that before I begin any work, I have worked with cathode ray tubes before. When not properly discharged and handled carefully they can pose a severe health risk or possibly death to the person conducting the repair. Please, do not try this at home. Or if you must... wear a hat or something.

Finally, when it's done, i'm considering that I may hook it up and take it for a weeks spin in place of my Intel iMac, just for kicks.

Wish me luck!

 

[phreakout]

iMac600, if you need parts, let me know. I've got a iMac DV SE with 500 Mhz G3, Firewire 400, that currently has a bad P.A.V. Board I need to get rid of. It's either that or I've got to spend the money I don't have to resurrect it. CRT is in working condition as well as the logic board. I even have chassis parts included. It was the model with a Sky Blue or Blueberry color case.

73s de Phreakout.

 

[John Hokanson Jr.]

I hope this doesn't seem like thread hijacking. It's kinda related...

What are the risks of disassmbling an iMac down to the CRT? I'm always heard that CRTs are oh-so-dangerous because of the huge residual voltage that can hold.

- John

 

[LCGuy]

Yes, when not discharged a CRT can hold up to 27,000 volts. However, there's also an even bigger risk of the CRT neck (which is VERY fragile!) being cracked or broken if handled incorrectly, which basically means broken glass everywhere, and bye bye CRT. Not to mention, if when reinstalling the analog board, you connect the anode cap (the big suction cap that goes on the back of the CRT) incorrectly, it could short.

 

[Christopher]

Yeah, I have first hand experience with a broken tube..

Still alive to this day.

 

[iMac600]

Well, it looks like the fault is in the PAV board itself. Not dead, but still very weak.

Solution?

The "donor" system arrived today. It's an Indigo G3, case is pretty scuffed but the internals are mostly good. Video and power components are in perfect working condition, although the hard disk is trashed (major clicking noises going on there). The perfect system to resurrect the iMac SE. This also means I can probably get away without separating the tube and PAV board- I can swap it in with a single swoop provided the divider plate and heatsink assembly matches. This will be determined as I begin to tear the machine down. Otherwise it means i'm up for a CRT/PAV job.

The rest of the components I had no plans for. 500MHz PowerPC G3 with 256mb of RAM. Perfect logic board for my other iMac, a Ruby, which currently has a 400MHz G3 with only 128mb of installed RAM.

So, the build begins!

Pretty sure I won't die in the process. I've bashed around with many a CRT from 21" monsters to little 9" Mac Classic displays. Yes they are fragile and contain an extremely high voltage, so following the proper guidelines and taking all necessary precautions is a requirement. not an option.

UPDATE - 4:22 PM: I've swapped the G3 600 board into the Indigo for a test run. Now the CRT in that machine is doing the same thing. The project is taking an unexpected turn here as i'm pretty sure the issue is with either the Logic Board or the Down Converter and not the Cathode Ray Tube or Power/Analog/Video board.

UPDATE - 4:30 PM: The 600MHz Logic Board is at fault.

 

[iMac600]

6:53 PM

The iMac is reassembled and seems to be taking well to the new CRT. The logic board eventually came good after a few resets (and after properly attaching all screws, go figure. Can anyone say "electrical earth"?).

Installing Mac OS 9.2 now for old times sake, plus to make the fine-tune adjustments. After that I may consider installing Panther as it was a bit of a flagship OS for this machine when I last used it so many years ago.

 

[iMac600]

Standing tall. Restoration complete.

I've officially named her "Kiva", after the development codename for the last generation Summer 2001 750CXe based iMacs. Now I just need to pick a full time operating system for it. Need something that matches the hardware and case around it. So far Mac OS 9 and OS X Graphite are in close competition for the title.

My camera isn't good enough to take a photo of the extreme brightness of the new CRT without dimming the entire photo down, so I haven't been able to get any powered up shots just yet.

 

[John Hokanson Jr.]

I'm impressed. Especially on how nice the external case looks. I actually salvaged all the Indigo Blue parts from my old 350Mhz, and I'm thinking about polishing them up a bit. Somebody suggested 400 grit sandpaper and metal polish, but I'm still researching that.

Disassembling this thing was the biggest PITA ever. Largely because the plastic has been exposed to so much temperature variation from the heat. It's extremely brittle.

- John