Maintaining Hardware / fesability of keeping hardware running

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josehill
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby josehill » Wed Nov 29, 2017 2:41 pm

VenomousPinecone wrote:We are fighting entropy and it is a losing battle.

I seriously will never forget the moment almost 30 years ago when I was wrestling with equations for my Physical Chemistry course, and I finally understood entropy at the mathematical level. Entropy has no mercy...probably the most sobering thing I learned in college. I was young and immortal until that moment! :lol:

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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby jwhat » Wed Nov 29, 2017 4:55 pm

Hi josehill & venomousepinecone,

ha ha ha ... as a poor sod with a physics degree, I have to admit you are right. We have been battling against entropy in parallel universes.

But the ignorant practical biologist in us refuses to give up the fight ;-)

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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby Shiunbird » Thu Nov 30, 2017 1:48 am

josehill wrote:I seriously will never forget the moment almost 30 years ago when I was wrestling with equations for my Physical Chemistry course, and I finally understood entropy at the mathematical level. Entropy has no mercy...probably the most sobering thing I learned in college.


Could you share something on the matter?
A short-ish read?

That sounds fascinating!
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby josehill » Thu Nov 30, 2017 7:44 am

Shiunbird wrote:
josehill wrote:I seriously will never forget the moment almost 30 years ago when I was wrestling with equations for my Physical Chemistry course, and I finally understood entropy at the mathematical level. Entropy has no mercy...probably the most sobering thing I learned in college.


Could you share something on the matter?
A short-ish read?

That sounds fascinating!


I'll look around to see if I can find something. The challenge is to bridge the gap between simple (but reasonably accurate) analogies about disorder (like throwing a deck of playing cards in the air and expecting them to land in numeric order, i.e. the chances of things becoming more disordered or "breaking" vastly outnumber the chances of maintaining the status quo or improving, or "errors accrue, and they kill us") and the collection of math skills and related knowledge needed to make you say, "Yeah, it really is true." I understood all the analogies when I was a teenager, but it took a lot of math and physics courses before I had enough working knowledge to have a breakthrough in understanding. I also have little doubt that a professional physicist in the field would consider the level of hard-won understanding I had in college to be woefully naive.

I had a similar experience "doing the math" for relativity. It's one thing to be told that the apparent mass of an object increases as it approaches the speed of light, in a way that ensures it never can reach the speed of light, but it's quite another to build up the math skills and physics knowledge that let you evaluate the equations and see it for yourself. It's when you go from "surely there must be a loophole that will give us warp drive, because I want to be Captain Kirk," to "Wow, we'd need an entirely new understanding of how the universe works to think about going faster than the speed of light in any useful way. It ain't happening soon."

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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby vishnu » Thu Nov 30, 2017 2:53 pm

Not to mention that time stops at the speed of light and the apparent size of the Universe shrinks to zero... :shock:
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby MrBill » Tue Dec 12, 2017 11:12 am

I took a bit of a vacation and have a bit of a clearer head now. Ditched my old crummy job, it gave me lots of free time to troubleshoot the problems i was having and get things back on track. I thank everyone here for the advice. I was having a real bad day with both my onyx machines developing issues. I still do worry about the long term for maintaining the machines, but as of right now, i have things back up and running.
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby GRudolf94 » Wed Dec 13, 2017 2:29 pm

I was thinking about this, and, in this thinking, I came to conclude the lack of documentation is a major roadblock in mantaining obsolete systems. Sure, one can poke and probe and maybe eventually trace a fault. But sometimes, without docs, you're lost and hopeless. Shamefully, SiliconGraphics systems are scarcely documented.

Simple parts and boards can be fabbed, and new prototyping technologies are taking that further, however, we have not a chance of replicating the functionality of custom ASICs that weren't documented, even less so if the subsystem in which they're integrated is also a black box. Big multilayer PCBs are also still beyond reach of the poor hobbyist, so too bad for us.
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby opcode » Fri Jan 19, 2018 8:10 am

I just popped my 4th Indigo power supply. I have been fortunate that Indigo and old Indigo hard drives (the big ones from back in the day) have been the only hardware I have had trouble with. Is the Indigo power supply difficult to recap/refurb?
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby opcode » Sat Jan 20, 2018 10:52 am

Of course as soon as I post a reply to this I turn my onyx2 on and I hear a pop then that burning electronics smell. Everything seems okay with the system. I took out the tape drive and rebooted. I’m hoping it was that drive. The smell went away. I am about to take my gdm4011p to a crt repair guy in an hour. The picture was perfect but now it just blinks amber. I’m hoping it’s capactitors.
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby Irinikus » Sat Jan 20, 2018 11:01 am

It seems like you're having quite a time with all the things blowing and all, my deepest sympathies. :(

At some point, all of our SGI systems are going to need to be recapped.

If a machine is left standing, for a long time, as mine generally do, it might eventually be wise to have it's power supply recapped before powering it up. (In order to prevent it from going off like a bomb, as it's powered up!)

For this reason, I'm going to retire all of my SGI's except for one machine (More than likely the Tezro). I will buy lots of spares for the one machine that I keep using so that I don't have to worry about acquiring spares for multiple machines.
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby uunix » Sat Jan 20, 2018 11:55 am

I wonder about the popping of power supplies. Is it occurring when you completely disconnect power - remove the kettle lead so speak. I ask because touching wood, since I have power going to my machines all the time, yet turned off and on, I haven't suffered that for a few years now.
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby Irinikus » Sat Jan 20, 2018 12:04 pm

If the machine is plugged in all the time, then parts of the power supply are always energised.

Inrush current is rather bad for capacitors, and the caps in a power supply are more likely to experience this phenomenon when the power supply is allowed to discharge completely as a result of the machine not being plugged in all of the time.

A well designed power supply should have circuitry in place to combat inrush current through it's filter caps though. (Placing resistors in series which the caps as they initially charge and then removing them once the caps are sufficiently charged, by making use of relays and a timer or current sensing circuitry.)

This feature is easily built into linear power supplies, but I don't know about switch mode power supplies though.
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby opcode » Sat Jan 20, 2018 2:36 pm

CRT repair guy total waste of time. There is a guy who services arcade machines and has a lot of services for crt monitors for the cabinets listed. I’m going to try him. I’m going to see if he will look at the indigo power supply as well. The 4011p is blinking amber and it looks like a h/v deflection , thermal failure looking it up in the manual. I’ve only had it for a few months. It’s pristine and the screen quality was perfect when it was working. It is worth the cost to fix it.
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby robespierre » Sat Jan 20, 2018 2:40 pm

That monitor has a diagnostic service port that may reveal more information about the failure.
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Re: Maintaining Hardware / fesability of keeping hardware running

Unread postby MrBill » Sat Jan 20, 2018 6:15 pm

I have to say, i have been working om my pdp 11/34 over the weekend, and the documentation is excellent. I have a full print set. everything. every circuit in the machine is laid out and documented.I was able to disassemble and manually repair the power supply. The manuals go a long way when trying to fix something. Then again, these machines are much simpler compared to a sgi machine.
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