G3 Troubleshooting

[Solar]

Hi. I have a dead slot loading iMac G3 (with firewire and VGA port), and I'm trying to determine where the
fault is. I'm not very knowledgeable on macs, but googling for a few hours it seems likely to either be the
logic board or, of course, the PAV board. I'm holding out hope it's the logic board, because while I don't
mind replacing that, the PAV board is far outside my comfort zone.

This is what happens. Power up, solid green light, slight click and 'chriping' sound from the machine (see
link below), then it just sits there, blank screen, green light, no chime. There is a solid green light on
the motherboard when powered up, no HDD or disc drive sounds. The machine does respond to the keyboard power
button but does the same thing. I have replaced the PRAM battery (old one was entirely dead) and used the
reset switch near the PRAM several times (only once between startup attempts), including when the machine was still
connected to power, and attempted to use "command+option+P+R".

Here's a sound clip of what it sounds like when trying to power it up. (Don't mind the clock in the background)

https://drive.google.com/file/d/0B8H0B5rF2we0bkExSGJHNVJQZHc/view?usp=sharing

I'm pretty sure it's the PAV, in which case I'll just have to give up, but I thought I'd ask just incase.

Thanks!

 

[Macdrone]

Its the power supply , its not that much harder than the motherboard, you could recap it pretty easy or get another but if your not comfortable I understand.

 

[Schmoburger]

Yep, definitely the Power supply by the lookooks of things. It's a bit more involved and daunting than the logic board but if you don't rush things, be organised with your workspace and get familiar with things first, you should be right. The hardest part is realistically seperating the top and front case plastics from the inner bezel without breaking anything to access the PAV board. WHilst I say this, beware that there is the potential for there to be residual high, possibly deadly voltages present in some components of the PAV board so you must have an idea of where these may be and be dilligent about where you put your fingers or tools.

This link to an entry on my blog will give you a pretty foolproof step by step as far goes taking the case apart and reassembling it later. It doesnt go into details about the PAV board as for the project that blog entry covered, this wasnt removed. My advice would be to google a teardown of the slotload iMac and also do some reading up on the procedures you should observe to safely work around exposed CRT's, CRT analogue circuitry and other high voltage areas such as Power supplies.

 

[Solar]

That's a pity. Thanks for the detailed reply though. Anything else, I'd try my best to fix, but high voltage stuff is a bit much for an amateur like me . I'm looking at another right now, which has a faulty disc drive. It's a slot loading, so I plan to swap the drive from my dead one to the new one. One quick question, there's a lot of large scary looking caps to the side of the disc drive, and my screwdriver will make slight contact when taking out the disc drive as a screw is right next to them. Is anything there dangerous to touch?

EDIT: It's a m5521, 1999 model, by the way. (The dead one)

 

[CC_333]

If you leave it unplugged for like a week or two, chances are that most of the potentially deadly voltages will bleed off, so the caps around the optical drive should be safe.

By the way, what color is it? Since it's a 1999 model, it's either Tangerine (orange), Lime (bright green), Grape (purple/violet), Blueberry (turquoise), Strawberry (pink), or Graphite (grey).

c

 

[Solar]

Lime, which was my favourite colour, too.

 

[Schmoburger]

If you turn it off switch the wall socket off, hit the power button a couple of times until it stops flashing the power button as though it is trying to power on. leave it plugged in for a day with the power turned off at the socket it should bleed the stored voltage out of *most* parts of the machine.

And as far as logic board circuitry goes, you shouldnt be overly concerned about the caps there as most of it is pretty low amperage anyway.... If you dont touch it whilst it's running (basically impossible... you shouldn't have a lot to worry about. It's the PSU and AV circuitry that is the most sketchy and still requires care as the amperage (which is the deadly part of electrical current) is a lot higher, and even with the bleed-down resistor functional, the CRT particularly can still sometimes store a residual charge for a while that might not be enough to kill you (though it can if it takes the right path or you have cardiac or certain neurological conditions), but will nonetheless knock you for six.

You have to be very clumsy to kill yourself with residual charge from a power supply circuit, but even I am very light footed around CRT circuitry, transformers and tubes. There is a method to disharging CRT's that is quite safe so long as you have the correct tool and adhere strictly  to the procedure and dont allow yourself or an uninsulated conducter you are holding become a short to ground. There is a fair bit of info on all this on the web if you feel like enhancing your skill set... if you arent comfortable still though, it may be best to avoid the area of high voltage, high current areas.

 

[Solar]

I see. Thanks so much for the information. I'll certainly start reading up on this stuff. Thanks!