Weak Power-Supply

The current computer ‘Phoenix‘ (I own several computers) has suffered from a string of malfunctions in the past, which I had trouble diagnosing the cause of.

I think I’ve found the problem: Its power-supply is weak in some way, which can also lead to low-voltage conditions that it subjects the high-speed electronics to. When high-speed logic circuits are fed low supply-voltages, the computer can spontaneously crash.

The reader may wonder how I know this.

When I’ve left the computer idling and come back to it, thus entering my password to dismiss the screen-saver, the case-fan speed seems to be stable around 3,500 RPM. But as soon as I fire up my Web-browser, the CPU usage goes from low-usage to nearly-100% usage for less than a minute, and as soon as that happens, the case-fan speed becomes unstable, sometimes resulting in a reading of ~40 RPM, which means that ‘The fan has stopped spinning.’ Then, as soon as I allow CPU usage to go below 5% again, the case-fan speed sometimes stabilizes again, within the same sitting.

Well there is no valid logic by which the motherboard would signal for the fan to stop spinning, or to slow down, at the moment the CPU usage is high. And so the only other explanation I can think of, is that the CPU – and possibly other circuits in the box – are drawing more current, and that this is causing a temporary dip in supply-voltage, just enough for the recently-installed fan to stop spinning.

But then, such a weakness also makes this computer more susceptible to such phenomena as brown-outs. Even though my eyes can see power-fluctuations that take place within a fraction of a second, I cannot see a low-voltage condition in the A/C power we are fed, if that low-voltage condition has set in over a period of minutes.

I might start looking for a new power-supply for this old box, rather than a new case-fan.

Continue reading Weak Power-Supply

The New Case Fan Has Failed.

According to this posting, my Linux-computer ‘Phoenix’, which is also my Web-server, once had a failed case-fan, and I had replaced it with a new one.

I knew that the old one had failed, both because my desktop widget showed it as only spinning intermittently, and because when I inspected it, with the tower-case open, I could sense with my hand, that the old fan had increased resistance to being turned. I assumed some sort of bearing failure.

The new case-fan did spin at full speed correctly, for some time.

But in recent days, I find that the new case-fan has failed again. I really have no explanation for this, but my widget now shows its RPMs doing the same thing they were doing, for the old case-fan, sometimes spinning, and sometimes stalled.

Now, I could undertake simply to replace it again, with a 3rd fan. But since the first repair did not work, I have no reason to assume that replacing the case-fan again would work. And so I am left pondering, what I should do.

Dirk

(Edit 05/20/2017 : )

Continue reading The New Case Fan Has Failed.

Continuing to Troubleshoot my Graphics Chip

The computer named ‘Phoenix’ has now been running for 6 days and 19 hours. It is approaching the point, where recently it used to crash. I have suspected that my graphics chip might be the problem, and that more specifically, this might have happened, because the graphics chip is only supposed to take 128MB of shared RAM according to the BIOS, but according to which it has been allocated 256MB, by the Linux software. It is an outdated graphics chip, which I have written about here.

Under Linux we have numerous tools that give us information about our machines, including the ‘‘ here:

phoenix_ram_2

I have already written that I cannot take the 70MB of shared RAM as an exact figure, of how much VRAM the chip is taking, which is actually system memory in this case, because there could be other processes using shared memory in some way. Yet, this is still an approximate estimate, and, since the amount being indicated is 70MB, the total amount of shared memory taken by my graphics chip, cannot be greater than 71MB.

This basically rules out one hypothesis for what might have been happening. Under normal use, the chip will not need more than 128MB.

Now, the fact that I have installed a new case fan, may or may not protect me from future crashes, since my other main hypothesis was, ‘Something could have been overheating on the motherboard.’

(Edit 02/14/2017 : )

And this is what my shared memory looked like today, 8 days and 23 hours after the latest reboot:

phoenix_ram_3

( 59+ MB – Stable )

Dirk

 

The new case-fan is variable-speed.

In this posting, I wrote that I had installed a new 92mm case-fan, on the old computer I name ‘Phoenix’.

One interesting fact about this is, that the fan is variable-speed. After a cold start, it only spins at 1000-1500 RPM. After that, if the computer has been idle, it spins at 2000-2500 RPM. And if things get toasty in there, it revs up to 3000, 3500 or even 5000 RPM.

Remarkably, this seems to be caused by drivers recognizing what they have to do, but did not require any setup on my part.

Dirk