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I recently was given a Power Macintosh G3 300Mhz minitower (having a bit of trouble confirming that but I'm mostly certain that's what it is(the case is labeled from 1997)) that had been outside for two years. The case is in very good condition and apart from some rust on the power supply and some of the metal frame(the metal on the side panel is quite rusted by the way) no parts of it look to be damaged. The logic board looks very clean and in good condition, but some of the metal on the ports looks like it might be a little corroded. I don't know much about desktops so this might be normal but there's a lot of loose cords and connectors inside of it that aren't plugged into anything. I see two hard drives and the floppy drive, and I think that's all it originally had, but is it ok for there to be so many loose cords inside? It hasn't rained for several months so there shouldn't be any water inside of it.

So is it safe to try to turn it on and use it without damaging it?

  • Welcome to Retrocomputing, great first post! – JAL Sep 6 '16 at 15:03
  • @Ezra - Can you grab a couple of pics, inside and outside? It would be interesting to see the extent of the corrosion. – Robotnik Sep 27 '16 at 0:05
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    @Robotnik - s1263.photobucket.com/user/ezraza/library/… That big closeup picture is the inside if the power supply. Also, would anyone like to explain these old ports to someone that's used to shiny new MacBooks? I haven't gotten around to working on it yet, but thanks for everyones help. – Ezra Oct 3 '16 at 21:05
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From your description, it sounds as though there is no fundamental reason why you shouldn't get this machine working again.

The main risk is something somewhere causing a short circuit. So, don't just plug it in and turn it on.

Firstly, give all the boards and plugs a good blow to dislodge all the dead insects and cobwebs. Pay particular attention to the power supply.

Then, wipe gently over every surface with a lint-free cloth (something like photographic lens cleaner cloth) moistened with a residue-free solvent (something like cigarette lighter fluid). Take your time, be thorough and make sure you cover both sides of every board. I would include unplugging every connector, jumper and on-board fuse and wiping the contacts.
If there is obvious corrosion on a port, a light rub should dislodge it.

Allow the fluid to evaporate completely and check again for any visible shorts.

You mention corrosion on the case itself. Check if the case is connected to the power supply earth (ground). If so, check that the corrosion hasn't broken electrical continuity of the earth. You can do this while the circuit board is out of the case.
You may also wish to try to remove or cover the rust on the case. How you approach that would depend on how bad it is. You would want to protect against rust flakes coming off in the future and falling onto the circuit boards.

One thing I have done in the past is to disconnect the power supply from the circuit board before connecting it to the mains. So, if there is something untoward, the circuit board is protected.

Plug it all back together and switch it on.

As to your question about loose cables: It is common to use a standard wiring loom that has contacts for expansion units. The production costs are lower. If you bought an expansion drive later, you just plugged it in. So I wouldn't worry about a couple of dangling leads provided they are clipped away safely.

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    On testing the PSU first, I did this with a PC recently. Unplugged the motherboard power connector and used a multimeter to test the voltages present on the plug before trying it connected. – Matt Lacey Sep 7 '16 at 4:04
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    I would recommend making sure the circuit is protected by a ground-fault circuit interrupter (GFCI), known by different names in different parts of the world, approved for use for protecting human life, before plugging in the computer and turning it on. Doing so provides an extra layer of safety particularly in case of a PSU problem. – a CVn Sep 7 '16 at 13:30

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