Salvaging a Failed Computer

English Open Chat
#21

oldcpu wrote:

>
> ken_yap;2292376 Wrote:
>> Usually I check by borrowing a PSU from another machine. It’s not too
>> hard, you only have to remove the 4 screws holding it to the case and
>> disconnect a few power connectors, all of which are keyed and impossible
>> to plug in the wrong way. There may be some subtleties whether you have
>> a 20 pin or 24 pin connector though.
>
> I may simply roll the dice and buy a new power supply unit (PSU) to
> avoid the risk of injury. … let explain …
>
> The PC I have with a PSU that I could try is my older athlon-1100. We
> have the PC neatly located under the desk connected to a hardware KVM.
> To remove it requires crawling under the desk, disconnecting all the
> connectors, and then pulling the athlon-1100 PC out. But I’m not young
> any more, and crawling under the desk is murder on my back (which is
> still sore from pulling out the dead athlon-2800). Then once the
> athlon-1100 PC is out and open, disconnecting the power connectors and
> removing all my wife’s carefully made tie wraps (as we put this old
> athlon-1100 together ourselves). Then when the test is over, doing all
> the above again in reverse and crawling back under the desk. Plus all
> the cables under the desk then need to be neatly re-arranged again which
> require one twist and move about in a confined space.
>
> That reads like a lot of pain …
>
> The athlon-1100 was the last PC my wife and I put together, and the
> main reason it was the last is both of us found the connector part of
> the assembly (trying to wrap the wires so they were neatly located
> inside the PC while still provide superb access for one’s hands to do
> various upgrades … etc … ) the most annoying part of the assembly.
> We told ourselves afterward, never again. We would rather pay someone 50
> euros to assemble a PC for us than do that again. … Well when I look
> at the price of a new PSU and the less expensive ones cost around 50
> euros.
>
> Now if I could only find that legendary fountain of youth, I might be
> able to reconsider my approach to this. :slight_smile:

I don’t even try to crawl under anymore. If I have to get into the
spagetthi pile behind/under the desk, I move enough junk from in front of
the desk that I can slide the whole desk out 3 feet or so and walk behind
it. Cables run off the back of the desk - feed holes are a no-no.

It also helps that the wife refuses to enter the cave…

–
Will Honea

#22

On 02/21/2011 03:47 AM, Will Honea wrote:
> It also helps that the wife refuses to enter the cave…

it is a fact that wives are greatest danger to the backs of computer
keepers…expecting us to keep it “looking neat and tidy”…

like Will Honea, i have full access to all sides of all eBoxes…but,
unlike him i do not have to slide the desk to have access, because the
top of the dining room table holds all electro-toys…[yes, it is a
mess]

on the other hand, a live-in cleaning lady would be nice too–but,
they generally run away screaming if i invite one in.

–
DenverD
CAVEAT: http://is.gd/bpoMD
[NNTP posted w/openSUSE 11.3, KDE4.5.5, Thunderbird3.0.11, nVidia
173.14.28 3D, Athlon 64 3000+]
“It is far easier to read, understand and follow the instructions than
to undo the problems caused by not.” DD 23 Jan 11

#23

oldcpu wrote:
> We then connected the volt meter to one of the CD/DVD drives power
> input. 0 volts even though power is being applied. But what was of
> interest was as soon as we switched OFF the master power switch on the
> back of the PC (ie on the power supply) there was a brief few second
> power surge that was immediately measured on the volt meter. This does
> appear more and more to be abnormal power supply behaviour.

Wild guess here, but it sounds to me that a switch may be failing. If
the ‘soft’ power switch on the front of the computer wasn’t making
contact, you might get these symptoms.

In terms of measurement technique, if it was me, I would check voltages
with the PSU still wired up to the motherboard. Either poke the probes
down the Molex connector to access the pins if possible, or access the
reverse side of the PCB. But I am used to using multimeters and I
wouldn’t recommend the technique if you’re nervous about slipping with
the probe.

#24

Checking the soft on switch is easy, just get a jumper wire and short the soft on line at the power connector to ground. You can find a pinout of the power connector if you do a search. The wire will be a distinct colour (not red or black for sure) and the ground wires will be black.

It’s not usual for a soft on switch to fail though, it’s just a momentary close switch.

#25

[quote="“ken_yap,post:24,topic:62196”]

Checking the soft on switch is easy, just get a jumper wire and short the soft on line at the power connector to ground. You can find a pinout of the power connector if you do a search. The wire will be a distinct colour (not red or black for sure) and the ground wires will be black.

It’s not usual for a soft on switch to fail though, it’s just a momentary close switch.[/QUOTE]

The thought occured to me, and I played with the switch a bit, but to get a good look at that switch I need to pull the PC’s two hard drives, and I was not too keen (read : I was too lazy) to try that. But I DO need to confirm that is not the problem.

The idea of doing a short on the soft line of the power connector is intriguing (to electrically force a power-on action), although unhappy visions of electrocuting myself in an attempt to do this check are also dancing through my head as a caution that is making me a bit reluctant …

#26

It may sound stupid, but did you check that the power lead is OK. My next try would be to check that the switch is OK (using multimeter with no power on the system. Thirdly, I would remove the power supply and check for blown fuses or swollen capacitors (the top of the cap swells up slightly when bad… 90% chance that the power supply is faulty.

#27

There aren’t so high voltages on the low voltage side of a PSU as to electrocute you. On the other hand there is quite a lot of amperage and you could cause quite a big spark if you shorted say the 5V line to ground. The PSU would immediately blow its fuse or cut out though, thus going dead for sure.

#28

oldcpu wrote:
> The idea of doing a short on the soft line of the power connector is
> intriguing (to electrically force a power-on action), although unhappy
> visions of electrocuting myself in an attempt to do this check are also
> dancing through my head as a caution that is making me a bit reluctant

You don’t need to worry about electrocution. All the high voltages are
sealed away in the PSU case. The only danger with probing the board or
components on it is that you might damage components if you accidently
short the wrong two pins together.

#29

Dave Howorth wrote:

> oldcpu wrote:
>> The idea of doing a short on the soft line of the power connector is
>> intriguing (to electrically force a power-on action), although unhappy
>> visions of electrocuting myself in an attempt to do this check are also
>> dancing through my head as a caution that is making me a bit reluctant
>
> You don’t need to worry about electrocution. All the high voltages are
> sealed away in the PSU case. The only danger with probing the board or
> components on it is that you might damage components if you accidently
> short the wrong two pins together.

Just for clarity, there is one high voltage hazard even with the power cord
removed: the capacitors inside the PSU itself can hold dangerous charges.

Of course to get to these capacitors you have to essentially remove the PSU
then open it up but I’ve seen more than one person try this. Fortunately,
all have just been treated to startling light shows when they short the
traces with a screwdriver rather than their fingers but it is worth noting
that there IS a reason for the warning labels :wink:

If the PSU is closed, the worst voltage you’ll see is 12 volts so the
personal hazard is nil. If you are worried, just take a loop of wire and
short all the leads coming out of the PSU to the black (ground) lead AFTER
you remove the power cord. That’s a good practice anyway as even through
all the skin resistance you can damage components by the voltage your
fingers can carry - but that’s in the same category as making sure you touch
the case before reaching in and touching the mb. That’s why we wear
grounding straps when we work on these things.

–
Will Honea

#30

Simple troubleshooting techniques can take you a long way. the PSU is a switching power supply that can be adversely affected by devices taking too much load.

  1. Switch (momentary one for power start/stop) - This switch can exhibit fail or chatter. Fail will result in no power when pressed. Chatter will show as a double click at the MBO power contacts so that when you press the button you actually get power-on/power-off as you push the switch. To see if this is your problem remove the 2 power pins on the MBO going to the switch. Short the contacts momentarily at the MBO (voltage at these pins is 1.5V to 5V at no more than 30mA, so a insulated mini screwdriver can safely do the test. If short test works replace switch with new momentary one.
  2. Defective drive: I have had 5.25" floppy, 3.5" floppy, CD/DVD, HDD drives all short out and go defective. Main switch on back of unit has sometimes caused a slight noise from hdd or floppy when you switch off the switch as a symptom. To check this, simply remove power cables from drives and test. If a drive has shorted, pulling it’s power and data cable (because a bad data array on the drive can load down the supply too) and doing a retest may bring things back to life.
  3. Defective MBO is quite common too. Unfortunately, checking whether it’s the MBO or a PSU will require swapping one of them out. PSU’s can become load sensitive which means that the PSU may work great with one HDD but gets progressively worse as more drives are added. MBO’s can cause excessive load if a) the always - on circuit that monitors the power-switch has failed, b) Memory has shorted on any one bank (memory can reach soldering gun temperatures in seconds!), c) Fan - shorts or d) MBO shorts including defective capacitors.
  4. Video Card failure seen most commonly when a lot of heavy graphics have been used and the fan on that board has failed. Vieo is best tested by installing on a working system to see if system can access it. If the fan does not come on on the video card (assuming it has a fan) this is a good indicator but is not inclusive.
#31

I would not suggest shorting output leads to ground on a switching power supply as there are sensitive components that perform load balancing that lie between the output leads and internal filtering Capacitors, and while you may discharge the Capacitors you may also damage the Capacitors and associated components.

#32

techwiz03 wrote:

>
> Will Honea;2293882 Wrote:
>> Dave Howorth wrote:
>> … If you are worried, just take a loop of wire and short all the
>> leads coming out of the PSU to the black (ground) lead AFTER
>> you remove the power cord. …
>> –
>> Will Honea
>
> I would not suggest shorting output leads to ground on a switching
> power supply as there are sensitive components that perform load
> balancing that lie between the output leads and internal filtering
> Capacitors, and while you may discharge the Capacitors you may also
> damage the Capacitors and associated components.

Good point. My shorting cable actually has a 50 ohm resistor soldered in
the middle. Question: how many computer users actually have a soldering
iron anymore???

–
Will Honea

#33

I have got one somewhere around the house… Can’t seem to find it though.

#34

Hi OldCPU, as long as none of the radial caps on the MoBo have domed or convex tops, and the shrink jackets show no signs of heat damage, discoloration or splitting that is a good sign. Most of the later Athlon MoBo’s also have the +3 volt supply regulators for the cpu and memory on board, those will be the TO220 devices mounted on heat sinks near the processor and memory. Very close to those regulators you will see 4 very small bypass caps usually blue or orange in color (a bit larger than a match head) if you see no signs of thermal damage I would go with a power supply.

My VIA-KT 880 Athlon XP-3200 MoBo with 4 GB DDR-2 wants 230 watts, add a couple of HD’s and a pair of optical drives and 500 watts will give you a good safety margin. I know you’re in Europe, stateside PSU’s are cheap, Follow this link, http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=3255392&CatId=1079 I live 30 minuets away from one of their outlets and would be happy to mail one if that would be more cost effective for you. It is a 115/230 volt and being an “off line switching supply” it couldn’t care less about the frequency.

My apologies if this sounds like psycho babble, just got back from a crazy weekend piano gig in Flagstaff AZ, I really need to go to sleep but still too keyed up, I either have to swear off Jazz, or Booze, or euphorics, or maybe all of it, I’m ‘gettin’ too old for this nonsense even if it is still fun…>:)
Cheers! ,…:stuck_out_tongue:

#35

Thanks, … computer hardware is a bit more expensive this side of the pond, but its not too bad. If I wanted to ‘go on the cheap’ and still give our local PC shop some business, I could purchase this LC-Power 350 watt power supply for 29.99 euro.

But I’m leaning more toward either this BQuiet 430 watt PSU for 56.99 or this BQuiet 350 watt PSU for 41.99.

I have not yet been able to conduct any of the suggested tests, as there is too much going on right now at home after work (plus I still have not fully shaken the illness I had last week, and 8 hours at the office totally exhausts me - I have no energy in the evenings). Possibly this weekend I’ll try.

I also note my wife and I (who live by ourselves in a very small apartment) have functional in our place two laptops (one 8 yrs old and one 3 yrs old) and 3 desktops (my wife has one and I have two) so to justify maintaining a 6th PC (ie fixing this 7 year old athlon-2800) is something I have not decided is worth while. Its just that I hate to see an other wise good PC (with 2xHD, 2xDVD, good nVidia PCI 8400-GS, and 2GB DDR-400 RAM) go to waste. … Decisions … decisions …

#36

Maybe not computer users, but technicians, and engineers especially those who make daughter boards for PC’s won’t be found without the almighty soldering iron!

#37

techwiz03 wrote:

> Maybe not computer users, but technicians, and engineers especially
> those who make daughter boards for PC’s won’t be found without the
> almighty soldering iron!

Maybe I’m just an old grouch, but my recent experience is that computer
techs have gone the way of auto mechanics: remove and replace. Even when I
was teaching EE several years back, the engineering curriculum at those
colleges were far too cerebral. That an engineer should get his/her hands
dirty was heretical and logical trouble-shooting was not worth the time
spent teaching it. I certainly appreciate my department chair at one
university who held the opinion that every engineering student should be
required to spend a couple of semesters actually maintaining the equipment
used in their specialty.

I will admit that assembly techniques like surface mount components limit
the repair potential without special equipment and many custom parts are not
even available outside the manufacturer but I am not impressed by operations
such as the Best Buy Geek Squad!

–
Will Honea

#38

I have to agree, but expand that to the broader tech industry too. Not too
many have honed the true skills of discrete trouble-shooting. And this loss
of basic ability holds so many back from reaching their true potential. I think
it’s fair to say we’ve made it far too easy to take the easy path, hmmmm!

Even when I was teaching EE several years back, the engineering
curriculum at those colleges were far too cerebral. That an engineer should
get his/her hands dirty was heretical and logical trouble-shooting was not
worth the time spent teaching it. I certainly appreciate my department chair
at one university who held the opinion that every engineering student should
be required to spend a couple of semesters actually maintaining the equipment
used in their specialty.

1+ for that! how can a engineer appreciate what he/she has never experienced?
I relate it too a comment found in Battlestar Galactica, and episode from the original
series where Starbuck re-activates a Cylon Robot that crashed his starship. “When
you were about to crash why didn’t you pull up? … We voted to consult the manual
and we were trying to find the instructions when the ground came up and hit us”

I will admit that assembly techniques like surface mount components limit
the repair potential without special equipment and many custom parts are not
even available outside the manufacturer but I am not impressed by operations
such as the Best Buy Geek Squad!

True and even layered boards further limit potential. When the majority of discrete’s
were sourced through America, UK, and Europe parts were not so hard to come by
but now they come from Taiwan and tend to disappear with relatively short lifespan.

I’m not a real big fan of Geek Squad and similar either, they know enough to just get
them into trouble then lack the skills to crawl out.

#39

It’s a real shame that the discipline of a master craftsman has been replaced with minimum wage recycling “specialists”. When I started out if you didn’t know
what a 6SN7, 12AX7, 5881/6L6GC was, or got to see the aspiring but woefully inept candidate’s body levitated nearly parallel to the floor, suspended by one finger like a Gilbert science gyroscope off of the plate cap on a 6146 in a SVT, well you just weren’t in electronics.

That poor kid, after he hit the floor I said, told you not to touch that, there’s 960 volts of B+ there. Bobby C. the service mjr, a clinically depressed man that could have been the model for Marvin the robot from Hitchhikes guide to the Galaxy, laughing like a maniac til he wet his pants, and he didn’t get shocked.

There was beauty and pride in old technology, a Hammond organ “tone wheel” assembly, completely mechanical, all those marvelous sounds and harmonics created by 144 spinning assorted star shaped disks with magnetic inductors and passive L C R filters, the little hi freq amp in a Leslie 144, a pair of 6V6’s clipped to square waves pukeing their guts out into a 15 watt Jensen compression driver through a spinning horn and Bob Moog’s system 55 modular with his 10 pole VCF and passive LC filter is what made Emerson, Lake and Palmer sound like God.

I can’t help it, I was piano tuner, keyboard tech, roady and monitor (fold back in England) engineer for many tours, during 1 stateside tour I spent an entire summer in my BVD’s bouncing around in a semi trailer keeping 1 of 3 “Mellowtrons” working, do you have any idea how challenging it is to stuff the tape magazines in a Mellowtron bouncing in a 110 degree trailer? You could drink three gallons of water and pee twice a day. That was with King Crimson, which was basicly Emerson, Lake and Palmer with Robert Fripp, yes I was there.

We all lost something, the personal rewards and pride that come from mastering a discipline of your choice, the feeling of accomplishment which only comes from hard work and beholding the end product. It gives you a feeling in your chest which if one has not experienced, I am truly sorry for them. In my country work ethic has unfortunately slipped into the shadows of oblivion and somehow I long and anxiously await for my turn to rejoin these lost, artistic and totally human endeavors. It just seems as if nobody wants to know how and why things work anymore, failure analysis isn’t about what failed but why it failed.

Now I’ll put the soapbox away for the night and close with this, a recent want add under employment: “Wanted Ept canidated for component level training”

#40

CFN7 wrote:

> It’s a real shame that the discipline of a master craftsman has been
> replaced with minimum wage recycling “specialists”. When I started out
> if you didn’t know
> what a 6SN7, 12AX7, 5881/6L6GC was, or got to see the aspiring but
> woefully inept candidate’s body levitated nearly parallel to the floor,
> suspended by one finger like a Gilbert science gyroscope off of the
> plate cap on a 6146 in a SVT, well you just weren’t in
> electronics.

Ah, shucks - you got me started :wink: My favorite sight in the lab was a
classmate of mine at the Academy taking the mandatory EE classes. During
the audio amp lab experiments, he held the plate lead to the finals in one
hand and never even felt a buzz. Then he leaned over that rock solid metal
bench and his metal zipper completed the circuit…

Spoiled his love life for a while, it did.

Time to go before the moderator berates us :wink:

–
Will Honea