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Beige G3 Strange Issues

IlikeTech

Well-known member
I just got a beige G3, and It had a bad power supply.  I replaced it with the an ATX unit, and after cleaning the board with alcohol, it booted up.  However, now it won't boot.  It chimes with ram installed, but I don't get any video.  If I remove the RAM, I get a crash. 

It doesn't seem to PRAM reset, and it has a fairly good battery in it. 

The CUDA Reset button doesn't help either. 

I have cleaned all the boards a few times now.

 

androda

Well-known member
How long are you waiting to see whether the video out works?  My beige g3 will often sit for two or three minutes inexplicably before suddenly the video comes in and the machine boots up.  Currently unknown cause.  Do you have the power supply jumper on the logic board set to the PC setting?

 

IlikeTech

Well-known member
Yep, I have it sit correctly.  I haven't let it sit more than like 30 secs tho.  Will give it a try.

 

Brett B.

Well-known member
Just for fun you should try booting as normal, wait a bit, then try command-control-power shortcut keys.  This bypasses the RAM test and usually you get video almost immediately.  

Have you tried different memory?  What about disconnecting everything from the logic board except the power supply, video, and keyboard cables?

 

just.in.time

Well-known member
Have you tried unplugging the hard drive(s)? My beige G3 takes a minute to display video when booting OSX. If yours has that issue AND is freezing in middle of boot, could leave you on a blank screen.

Also, any PCI cards installed?

 

ArmorAlley

Well-known member
It sounds very unlike Apple to allow one just put in a generic ATX PSU and let it work.

I wouldn't be surprised at all if a slight modification would need to be made.

My guess is that you've blown some little component (like a capacitor) on the motherboard, although I am, by no means, a technical person.

A good high resolution picture of the motherboard would allow those who can see these things to confirm or deny my guess.

 
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Zippy Zapp

Well-known member
I have a G3 Tower that does the same thing on first power on.  It will not display video when I first turn it on until I soft reset it with Control+Command+Power Key (as someone already pointed out above) and then it works fine until the next power off cycle.  I think it has something to do with the aftermarket CPU upgrade that is in the ZIF socket.  Does yours have an aftermarket CPU upgrade, by chance?

 

Franklinstein

Well-known member
The power supply in the beige G3 minitower, like that used in the other G3/G4 tower Macs until the Gigabit models (which had a 28v line for the new ADC monitors), is basically a standard ATX unit but with slightly longer cables. It's real easy to install a higher-wattage ATX unit in one of those.

Because the beige G3 MT's Gossamer logic board was designed for use in multiple enclosures with multiple power supplies, there is a jumper on the bottom rear of the logic board that says MAC SUPPLY/PC SUPPLY. If your power supply is from an ATX unit or a MT, the jumper is on the PC SUPPLY side. If you have a DT or AIO, it's on the MAC SUPPLY position.

I had a G3 MT do a similar thing where it powers up but won't boot. I only got it to function properly by doing crazy combinations of removing components and then trying to power up.

I tried:

With ROM

With no ROM

With RAM in various configurations

With no RAM

With processor (original or upgraded)

Without processor

Changing the system bus speed to a different value (66, 75, or 83MHz)

Changing the processor speed jumpers (lower and higher than original)

With each iteration I pressed the CUDA reset button and there was not a PRAM battery installed.

Eventually the system decided to function again and I tweaked it to run an 83MHz bus, 375Mhz processor, 384MB RAM, Voodoo3, combo USB/FW card, and a fast SCSI card. I don't know what ultimately made it work but I put it all back together and it has been pretty reliable since.

 

register

Well-known member
1. Once, I bricked my beige G3 Desktop by installing Dantz Retrospect software. Afterwards it came back to life only after proper use of the CUDA reset button. I remember that there is a recommended sequence to use this button.

2. Large amounts of RAM on old Macs cause an unfamiliar prolonged duration of the RAM test. If the RAM is good, just turn off the RAM test in the boot process by unchecking that option in the Memory cp. Note: You need to depress the key combination Command-Option while opening the cp to bring up this option :)

 

beachycove

Well-known member
Overclocking a G3 too far will cause problems. You might check the jumpers to see if someone has been tinkering before you got the machine.

 

AlpineRaven

Well-known member
By now, I have noticed Beige G3s are starting to have issues that I have came across to, its the caps that will need replacing.

I just restored Beige G3 Server 333mhz model and it was having so many issues, replaced the caps - problems solved.

Cheers

AP

 

demik

Well-known member
It sounds very unlike Apple to allow one just put in a generic ATX PSU and let it work.

I wouldn't be surprised at all if a slight modification would need to be made.

My guess is that you've blown some little component (like a capacitor) on the motherboard, although I am, by no means, a technical person.

A good high resolution picture of the motherboard would allow those who can see these things to confirm or deny my guess.
No it works just fine, you just have to move a jumper.

The reason behind this as far as I remember, is that some weird education G3 machine sold in US used an ATX PSU at some point of his life. It's this one : https://www.macstories.net/mac/the-power-macintosh-g3-all-in-one/. It used a classic G3 Motherboard.

Looks life the video circuit is "dead". Do you have another video card to check that out ? Like @AlpineRaven said, you may need a recap.

 

IlikeTech

Well-known member
I wound up salvaging what I could and getting rid of the rest of the machine, as it was a total rust bucket, not to mention the problem with the logic board.  I did get some nice parts out of it though!

 

error1

Member
By now, I have noticed Beige G3s are starting to have issues that I have came across to, its the caps that will need replacing.

I just restored Beige G3 Server 333mhz model and it was having so many issues, replaced the caps - problems solved.

Cheers

AP
What kind of issues? It would be nice to know some of the symptoms, I have trouble with sata/ide drive corruption on mine unless i run it off a slow scsi2sd drive. It will often just lock up doing heavy IO from the cdrom drive too, it's been really frustrating. Did you just recap the small smd cans or the large electrolytics too?

 
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