iMac G3 service and rebuild (with MacEffects inner bezel)

displaced

Tinkerer
Nov 2, 2021
54
48
18
Kent, United Kingdom
Hi all,

I've had my late nan's indigo iMac G3 DV sat disassembled on my office floor for the past 4 years. Like many who have tried to service these old machines, I had the extremely brittle inner bezel crack into a million pieces during disassembly.

I managed to catch MacEffects' Kickstarter 18 months or so ago, and my new replacement inner bezel arrived yesterday!

Now, since so much time has passed, I don't even really remember the condition of this Mac I have in pieces. I know I suspected some potential flyback weirdness, so I picked up a second machine that's in pretty rough cosmetic condition to use as a spares machine. That one died after a few hours of use (no signs of life at all), but hopefully it'll serve as a standby should I need to borrow any parts for my main machine.

Anyway, I suppose I'm posting just to record my adventure! And to be open to any tips or suggestions that might help along the way should I hit any problems (I'm sure I will!).

So, at the moment, the state of the machine is:

  • Fully disassembled.
  • All plastics cleaned and polished.
  • CRT lightly dusted and put somewhere safely away from any chance of accidental knocks.
  • Analog, down-converter and logic boards cleaned and inspected. No visible causes for concern, but I reflowed the bigger pads on the analog board around any hot-spots just in case.
  • No apparent signs of cap leakage on any of the three boards. No bulging caps.
  • No battery leakage. Removed and will be replaced with one of those cool little button-cell replacements.
  • CRT neck-board looks ok at a glance, but I've not yet removed it from its aluminium shell.
  • Fuses test OK, caps will be tested in-circuit soon (not ideal, I know, but at least I can tick some off as being good)
  • Flyback, HV cable and anode cap all in physically good condition -- no external signs of arcing, heat damage.
Very much hoping I can bring this back to life as it has a fair bit of sentimental value. There weren't many septuagenarians using their own iMac to do their primitive early-2000s online banking and ordering Christmas presents for the family from Amazon back when it only sold books. She loved her computer and was so excited when we got our first cable internet service (a blistering half-megabit) and no longer needed to tie up the phone line! It came with OS9 and 10.0.3 dual-boot. Nan used OS9 whilst I often rebooted into X -- painful though it was, it was new and exciting.

Anyway, will keep this updated for anyone who's interested!

(edit: oh! I actually found an old thread I made on here when I first started the disassembly four years ago! https://tinkerdifferent.com/threads/imac-g3-dv-refurb.463/ -- I must've given up as soon as the bezel disintegrated.)
 
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displaced

Tinkerer
Nov 2, 2021
54
48
18
Kent, United Kingdom
Right! Well, I've got it reassembled as far as needed to power it on. No way I'm putting that tricksy outer shell on until it's working 100%!

Results are:

  • No pops, bangs or flames after connecting AC!
  • Does make a high-pitched whine after supplying AC. The whine varies a bit before settling, but doesn't go away.
  • On pressing the power button:
    • LED illuminates
    • Familiar clonk sound of the degauss ring
    • Staticky noise heard and... the CRT comes up with the Finder/Question Mark icon! Excellent!
    • The display's got a significant yellow gradient, lighter on the left and quite yellow indeed on the right.
    • No weird whistles, noises, crackles!
  • On power-off, the high-pitched ascending whine starts again, just like when AC was originally connected.
Interestingly, it won't fully start up again without having power completely disconnected for a few minutes. Until that's done, the power LED will turn on and it'll sound like the CRT's started up (static noise, degauss thud), but no picture appears.

So.... I think this feels caps-y to me. Maybe on the down-converter board?

(there's so many capacitors on this machine -- I'd like to at least narrow it down to a board before I start pulling and testing caps!)

As for the weird tint... any ideas appreciated!

Cheers,
Chris

(photo of the discolouration for reference)
iMac Discolouration.png
 
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