[G4] Old mini or other machine for cheap/free?

[Kristen R]

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On Feb 23, 2012, at 9:55 AM, Amir 'CG' Caspi wrote:

> Hey all,
>
> 	My old G4 tower finally died... not sure why, but it won't boot  
> even from a CD/DVD any more.  The firmware portion of booting works  
> (I can select the boot drive using the Option key, or boot into Open  
> Firmware, and I get the initial gray apple), but it looks like the  
> "main" boot sequence just never starts (I never see the progress  
> circle on the gray apple).  I tried disconnecting any and all hard  
> drives, swapping RAM, etc... seems to me something on the mobo has  
> died.  (The machine had a NewerTech CPU upgrade so maybe that's what  
> finally went kaput.)
>
> 	In any case, this machine was being used as a media server, so I  
> need something to replace it (assuming my hard drives still work).   
> Does anyone happen to have an old mini (G4, intel, whatever) that  
> they no longer want and are willing to let go for cheap/free?   
> Another tower (G5 or better) would also be fine but the mini's small  
> footprint and low noise is far more desirable.
> 	I've looked on Craigslist and saw some old Minis for about $300,  
> but that's not a great price for a more-than-3-year-old machine when  
> I can get a brand new one for about $500.  So, I thought I'd ask  
> here, in case someone might have one collecting dust in a closet and  
> wants it to go to a good home for cheap or free. =)
>
> 	Let me know...
>
> (Also if you have any idea on resurrecting the old tower, let me  
> know... but I'm pretty knowledgeable about computer innards and no  
> combination of things got the machine to boot, whether from internal  
> drive, firewire drive, CD/DVD, or anything else.  The battery and  
> firmware are fine since the initial sequence works, but the post- 
> firmware boot, when the CPU needs to run, doesn't work, which is why  
> I suspect the mobo.)
>
> Thanks!
>
> -- 
> 						--- Amir
> _______________________________________________

	As I think back over my 11 years of electronic servicing something  
here sounds familiar. That of turning off a product to find that it  
can't start back again. What I have experienced in the past are filter  
capacitors which get old and dried out. The internal resistance climbs  
and the end result are caps that can't filter very well and feel hot  
to the touch. Eventually they fail to function. Usually these  
exhausted caps are in the power supply and using an oscilloscope you  
can check if ripples are being filtered. If not then the electronics  
are subjected to said ripple as well with the overall result of less  
voltage for the electronics with an AC signal riding on the DC  
voltage. Microprocessors just hate that kind of environment and can  
burn up. If you attempt to read, lets say the 12 volt line with a hand  
held volt meter it would lie and say 12 v. Because a volt meter  
displays an average voltage only and can't read the high frequency AC  
signal. Thus the desire for an oscilloscope. To know for sure the  
power supply needs to be substituted with a known good one, or the  
output voltages substituted. I use to put an external adjustable  
voltage on the output of such a supply and kick it up a tad (no more  
then .5v usually) If life could be brought to the device then I knew  
caps in the power supply were a problem.

	You can check caps by touching the tops of them, those which have an  
imprinted cross on them. That imprint is actually the vent cap. When a  
cap is going to explode the vent cap expands and opens up. That way  
the gasses inside the cap can be released without the explosion. You  
can look for just such a situation by leaving your computer unplugged,  
open up the power supply and feel if these caps have a raised top. If  
so they have been hot and are expanding. They are defective and must  
be replaced. This method isn't fool proof but only helps to catch the  
worst of the bunch. Such caps usually have the plastic wrapping which  
has turned color or looks too small for the canister they surround.  
Again a function of too much heat. You can also look on the mother  
board as well for raised tops on these electrolytic capacitors. The  
only solution is replacement of the capacitor.

A thought for you

Kristen

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