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Posted: Wed 30 Jan 2013, 18:18
by Flash
In my experience, the chance of a RAM failure after the initial burn-in period is approximately zero. If it lasts a week or two, it will almost certainly outlast the motherboard -- and then it will be obsolete and useless.

Posted: Wed 30 Jan 2013, 19:02
by starhawk
Flash, I hate to tell you this... but that's not quite right.

My mother has an HP Compaq tc4200 "convertible" laptop/tablet system. Runs XP because "you get what you pay for", etc. :roll: After a while it started bluescreening. I changed one of the RAM sticks out, and the blue screens have yet to come back.

Mind you I had purchased both of the sticks in that machine, about a year before.

Posted: Wed 30 Jan 2013, 20:10
by Amgine
Flash wrote:In my experience, the chance of a RAM failure after the initial burn-in period is approximately zero. If it lasts a week or two, it will almost certainly outlast the motherboard -- and then it will be obsolete and useless.
Not true, my Dad had to send his back in after they failed, It was used RAM, from a gaming computer.

Posted: Wed 30 Jan 2013, 22:09
by maddox
I think Flash was talking about an initial burn-in period of the RAM :run a looping ram test prog for a week or 2.
makes sense -> usually used in servers.

My mistake , been in france visiting, brought some 220V power supplies with me with continent plug adapters (aus/gb/us):
laptop,usb charger,oscillo,small TX/RX ...
wondered why some equipment smoked after a while... :(
I found out the painfull way $$$, france uses a 230-240V power grid

Posted: Wed 30 Jan 2013, 23:09
by Amgine
maddox wrote:I think Flash was talking about an initial burn-in period of the RAM :run a looping ram test prog for a week or 2.
makes sense -> usually used in servers.
Ok!

Re: Our Dumb Mistakes

Posted: Thu 31 Jan 2013, 14:16
by postfs1
To reedit up to date.

Posted: Thu 31 Jan 2013, 16:50
by greengeek
This is not Puppy related - but years ago I was installing a computerised voicemail interface unit into a Telecom exchange. My field of experience was with the computer side of things - not the details of how the phone network operated. All I knew was that the phone network operated off 48 volts. "Thats not enough to kill you but take care anyway" was what they told me.

Anyway, these interface units ("Summa Four") had substantial red and black wires coming out of them, and these had to be connected to the massive buss bars running through the exchange. Naturally I connected the black wire to the Ground buss, and the red wire to the 48v buss. Everything was great until I turned on the new unit.

That was when I learned how much magic smoke they compress inside electronic components!

Turns out that telephone exchanges run on NEGATIVE 48 volts so the red wire goes on the ground buss. Doh! Who's stupid idea was that??!**!##%?

Posted: Thu 31 Jan 2013, 20:04
by Flash
When designing with vacuum tubes, it greatly simplifies the circuit designer's job to assume a negative ground, so negative ground became the natural choice as electronics grew into something useful. Before that, it didn't matter much which polarity was "ground". The phone system predates the development of vacuum tubes by decades. They probably flipped a coin to decide which side of the battery to ground, but once positive ground became the standard throughout the phone system, it would have been nearly impossible to change.

I remember when cars had 6 volt batteries and at least some of them grounded the positive side. I don't know if they all did. The original VW beetle put its 6 volt battery under the rear seat, and a heavy passenger could short it out.

Posted: Thu 31 Jan 2013, 21:18
by prehistoric
greengeek wrote:This is not Puppy related - but years ago I was installing a computerised voicemail interface unit into a Telecom exchange. My field of experience was with the computer side of things - not the details of how the phone network operated. All I knew was that the phone network operated off 48 volts. "Thats not enough to kill you but take care anyway" was what they told me...
You wouldn't have lasted long in the environment where one of my OLD friends learned about digital electronics, logic and computers. He started off working INSIDE a computer -- Whirlwind I.

The microcoding was done with diodes clipped between bus bars about as big around as your little finger. For electronic convenience some of those bus bars were floating at 400 volts.

Oh, BTW, the machine blew a tube almost every time it was turned on, so debugging was done with the power on.

I don't dare tell him about how bad I have it today.

Posted: Thu 31 Jan 2013, 23:57
by Dewbie
First I thought several floppy drives were bad...
Then, no, it's the floppy disks themselves...
(Neither assumption was correct.)

There's often enough variation in head alignment between drives that a floppy disk written with one won't work with another. So you have to write the disk with the drive that it will be used with.

Posted: Fri 01 Feb 2013, 00:03
by greengeek
prehistoric wrote:You wouldn't have lasted long in the environment where ....... some of those bus bars were floating at 400 volts.
True enough. I wonder what the frying time of human flesh at 400v is. 60 seconds maybe?? Mmmmm, smells like chicken...

That reminds me of another mistake I made - I was given the job of replacing the faulty "ON/OFF" switch in an 80 column card punch and I happily yanked the spade wires off the back of the switch - having forgotten to unplug the cord from the wall. Zzzzzt.

I managed to throw the switch right across the room and swore like a trooper, much to the customers amusement. Lesson learned.

Posted: Fri 01 Feb 2013, 00:31
by puppyluvr
:D Hello,
LOL...
I recently had a box go down after moving it.. Video failed completely.. Nada..
Had a geforce card in it, which I assumed had failed.. Removed it and attached to the onboard intel, reset the jumpers, and rebooted.. Still nothing at all.. Not even the bios framebuffer.. Crap.. Removed the disks, the cd/dvd, and replaced the ram, to no avail.. Checked all the jumpers, the ram slots, even tested the MB clip on the power supply.. Only after giving up in disgust after a few hours, when I removed the tower from the desk, did I realize I had plugged in the wrong monitor cord.. :roll:
I once turned off the wrong breaker to a 440 volt 60hp power source, and then stuck a screwdriver into a box, and blew the end off it, and my finger..
The video card thing still pissed me off more.... :wink:

Posted: Fri 01 Feb 2013, 03:28
by 8-bit
At one time, I worked as a millwright at a small lumber mill that made agricultural stakes.
I was also a regular worker there since it did not require a full time millwright.
I had another worker complain to me that he was being shocked by a machine he was feeding.
I touched the machine and did not get shocked so I thought I would investigate further.
When I did not get shocked, I was standing on a wooden floor.
I then went to clean out some wood on a trough conveyor and happened to touch the machine in question.
I now know what it feels like to be the ground for a 440 volt 3phase circuit.
It turned out that when the mill was originally wired, the conduit was used as a ground.
The conduit had separated and wore through one of the power wires.
And with the conduit separated the machine had what they would call a floating ground.
So anyone that was grounded and happened to touch the machine completed the circuit.
Not a good thing!

I had the machine then shut down, locked out at the breaker, and established a good ground for it as well as repairing the bad wiring.
But I did learn that when one goes to test that a meter is a lot safer than touching the machine to check for a short!

I guess you could say I got recharged that day!

Posted: Fri 01 Feb 2013, 04:23
by lwill
Not Puppy, but linux.
I updated to Fedora 18 with KDE on one machine and since then the "device notifier" applet would always ask for root password to mount cd/dvd/usb/sd drives when inserted. Never had before. No biggy, but annoying.
Spent half the day searching for reasons. Permissions, settings, mounting settings. Lots of google.
Turns out in the "default applications", the default file manager was set to "Konqueror ROOT" for some reason. I have an icon on the tool bar set to open my home folder that uses Dolphin (which is the normal fedora default) so I never try to open a directory directly and never actually used the "default" file manager.
.
.
On further thought, I may have done it to myself at some point. I was working with Android / linux on a Mele 2000 using sd cards to transfer stuff and needed to be root to modify files on them.

Still half a day I lost fixing it!!

Posted: Fri 01 Feb 2013, 15:57
by prehistoric
lwill wrote:...Still half a day I lost fixing it!!
Only half a day? Hardly worth mentioning.

How about the better part of a stressful week?

This story relates to the earlier business about high voltage in a strange way, we were simulating a device which used a traveling-wave tube -- because not only did these things cost about $15,000 apiece, there was a real problem of losing students if they reached into the case without turning the power off. (We're talking thousands of volts, with kilowatts of power.) It also has some relevance to assumptions about the polarity of ground.

Naturally, we were dependent on an expert instructor for testing our simulated device. Nobody wanted to fool with the real thing, even if we were allowed to. (The device was classified, which made it hard to access data about it.) The one expert we had that week told me I had one control "backwards" on the simulator, as opposed to the real device. I questioned him about this with a graph of the performance of some parameter versus voltage on that knob in front of us. When I thought I understood, I went off and reprogrammed. This was not a simple task, because of other factors that would take us too far afield. Any substantial change cost me hours of work. I went through this drill three times. Each time it remained "backwards", and I became more confused.

On the last day of this fiasco I walked into the room housing our simulator, and saw a technician resoldering the wires on the potentiometer controlling the (simulated) voltage which was the problem. It turned out what our expert meant by "backwards" had nothing to do with the voltage on the graph; he meant the real knob rotated counterclockwise to increase voltage. My original program had been correct, but under pressure of all the changes made in a hurry I was no longer sure which version I should use.

I ended up reprogramming that control from scratch one last time. It only took me a little over an hour, because of all the practice I had had. A simple question about clockwise versus counterclockwise could have saved most of a week. Fortunately, errors with simulated voltages don't kill people.

Posted: Fri 01 Feb 2013, 18:07
by greengeek
prehistoric wrote:...he meant the real knob rotated counterclockwise to increase voltage.
Interesting the assumptions we make. My guts tells me that it is just plain "wrong" to have the voltage increasing when you turn the knobby counterclockwise - but there is no real justification for my rationale. Whoever wired up the real knobby in that direction was a knobby themselves.
:-)
Or maybe thats just how things go in the northern hemisphere? Like bathwater draining the wrong way...

EDIT: I suppose if the knobby was marked "ATTENUATION" then it MIGHT be ok to be decreasing the voltage in a clockwise direction. Otherwise its just not ok to do that. Never. Not ever. (Unless there's a good reason). :?

Posted: Sat 02 Feb 2013, 00:47
by puppyluvr
:D Hello,
CW is on, CCW is off..
"righty tighty, lefty loosey" (except old Mopar.. :roll: )

As a teenager, while hunting deer with my younger step-brother Bobby, I witnessed him urinating on an electric cattle fence... :shock:
After the convulsions went away, and the screaming subsided, and I quit laughing enough to check, he seemed to be OK... :roll:

Posted: Sun 03 Feb 2013, 15:36
by prehistoric
greengeek wrote:...Interesting the assumptions we make. My guts tells me that it is just plain "wrong" to have the voltage increasing when you turn the knobby counterclockwise - but there is no real justification for my rationale. Whoever wired up the real knobby in that direction was a knobby themselves.
:-)
Or maybe thats just how things go in the northern hemisphere? Like bathwater draining the wrong way...

EDIT: I suppose if the knobby was marked "ATTENUATION" then it MIGHT be ok to be decreasing the voltage in a clockwise direction. Otherwise its just not ok to do that. Never. Not ever. (Unless there's a good reason). :?
There was an excellent reason -- all the other controls had the opposite polarity. The graph I was using as a reference didn't mention that. I suppose they just assumed anyone familiar with the device would know.

I will note, in passing, that modern traveling-wave tubes are designed with the idea that it is ridiculous to have a mere human technician directly controlling each parameter. There are sophisticated circuits between people and those adjustments. That simulator was scrapped long ago.

Posted: Sun 03 Feb 2013, 15:40
by prehistoric
puppyluvr wrote:... As a teenager, while hunting deer with my younger step-brother Bobby, I witnessed him urinating on an electric cattle fence... :shock:
After the convulsions went away, and the screaming subsided, and I quit laughing enough to check, he seemed to be OK... :roll:
Does he have any children?

I know of an entire fraternity which is reproductively challenged as a result of an initiation involving pissing on a running lawnmower.

Posted: Mon 04 Feb 2013, 00:00
by Dewbie
prehistoric wrote:
I know of an entire fraternity which is reproductively challenged as a result of an initiation involving pissing on a running lawnmower.
An electric mower?
Or was it blade-related? :roll: