I work at a university. In the science building in a lab class room the computers are having problems with the keyboards shutting down. The computer staff thinks it is a power problem. I monitored the voltage for a day. The voltage had a flucuation range of about 5%. That seems to me normal. Any other suggestions.
computer problems
- Thread starter JdoubleU
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
The keyboards shut down, and nothing else shuts down? 
The mouses continue to work, and the monitors, and the printers, etc.? That would be a strange symptom.
1. How many computers are involved, and what do they have in common?
2. Has anything changed recently? Did all the staff get new keyboards (at a bargin price, no doubt)?
3. How does this problem manifest itself? Do all the keyboards stop at the same time, or is it a matter of getting frequent reports of "my keyoard just stopped working" from one or more staff members each day?
4. How do they know that the keyboard shut down? Nothing happens when they type? Does this happen in the middle of typing a line, or do they come back from lunch and notice the problem?
The mouses continue to work, and the monitors, and the printers, etc.? That would be a strange symptom. 1. How many computers are involved, and what do they have in common?
2. Has anything changed recently? Did all the staff get new keyboards (at a bargin price, no doubt)?
3. How does this problem manifest itself? Do all the keyboards stop at the same time, or is it a matter of getting frequent reports of "my keyoard just stopped working" from one or more staff members each day?
4. How do they know that the keyboard shut down? Nothing happens when they type? Does this happen in the middle of typing a line, or do they come back from lunch and notice the problem?
robbietan
Senior Member
- Location
- Antipolo City
Jakewhis said:
Did you check if the computers have their equipment grounding connected to a single reference point? I have seen computers and their peripherals go crazy when their grounding cables are connected to the nearest convenient metal part of a char, table, etc.
76nemo
Senior Member
- Location
- Ogdensburg, NY
???
???
Does the lab hold it's own designated neutral?
???
Does the lab hold it's own designated neutral?
brian john
Senior Member
- Location
- Leesburg, VA
Please elaborate!
Keyboards, TTBOMK, are powered by the computer they are connected to through the PS/2 or USB interface (unless they are wireless, in which case they are powered by batteries... but the interface transceiver most likely gets its power from the computer; note some recharge cradles are dual powered with the recharging powered by a wall wart). That power is routed through the MOBO which has voltage regulators on such and this is even redundant to the PSU voltage regulators. I doubt very much the integrity of the PSU power supply would cause ONLY this problem... meaning the computer most likely would exhibit other problems too... and it is even less likely that several to many computers would exhibit the same problem.Jakewhis said:
In my opinion it is a software driver problem, but that depends somewhat on the symptoms and the events under which the symptoms occur. Sometimes it is simply the manner in which such driver was installed. For example, I recently powered up a new computer that I assembled and loaded Windows Vista Ultimate. I connected a Logitech wireless keyboard mouse combo and had no problems with it until installed it's SetPoint software driver, which enables use of special features. After I awakened my 'puter from Sleep state the keyboard and the mouse did not function. I could not do anything on my 'puter until I did a reboot. After uninstalling the SetPoint software the keyboard and mouse once again functioned normally on wake... but I lost the use of special features.
Having searched the web, it seems this is a common problem on WIndows Vista, especially with USB-connected keyboards.
A Logitech support rep suggested installing the SetPoint software driver in a "clean" mode. I did that and I've only had 'em freeze up once since.
ELA
Senior Member
- Occupation
- Electrical Test Engineer
What recovers the keyboards?
Could be static electricity.
I used to have my keyboard hang up all the time when I would walk across the floor to my desk and touch the keyboard. A large static charge entered through the keyboard electronics and upset it.
Unplugging the keyboard and replugging it in again would reset the electronics.
This happened more often in winter when the air was dry.
I ended up putting a small static dissipative pad near the keyboard and would remember to touch it first before touching the keyboard.
Could be static electricity.
I used to have my keyboard hang up all the time when I would walk across the floor to my desk and touch the keyboard. A large static charge entered through the keyboard electronics and upset it.
Unplugging the keyboard and replugging it in again would reset the electronics.
This happened more often in winter when the air was dry.
I ended up putting a small static dissipative pad near the keyboard and would remember to touch it first before touching the keyboard.
robbietan
Senior Member
- Location
- Antipolo City
brian john said:
the case I have seen have some of the computers' equipment grounding connected to some wires that the people there say can be the neutral or ground wire. they cannot even say for sure. had the problem solved when all equipment grounds were connected to a new ground line.
wirenut1980
Senior Member
- Location
- Plainfield, IN
My $ is on Smart $
My $ is on Smart $
I am betting it is a software/driver issue.
My $ is on Smart $
I am betting it is a software/driver issue.
charlie tuna
Senior Member
- Location
- Florida
you've answered your own question:
four computers on a circuit ----- thats fine
sharing a neutral---------------- thats bad
three phase--sharing a neutral with two other circuits----- thats real bad..
a place like this requires dedicated circuits. re-pull and provide separate neutrals to each circuit....
four computers on a circuit ----- thats fine
sharing a neutral---------------- thats bad
three phase--sharing a neutral with two other circuits----- thats real bad..
a place like this requires dedicated circuits. re-pull and provide separate neutrals to each circuit....
- Location
- Massachusetts
charlie tuna said:
I have to disagree with that as a general statement, all equipment shares a neutral once it reaches the panel.
Assuming a correctly wired circuit a computer can not 'tell' if it is supplied from a two wire or MWBC.
charlie tuna
Senior Member
- Location
- Florida
example: we bid a tenant build out for goldman-saks --a brokerage firm that had row after row of work stations over a computer flooring system. the bid prints showed common neutrals to all work stations--and thats the way i bid it!! we got the job and they had a "pre job site meeting" to talk about the demo work. the engineer was in attendance and after the meeting i asked him(in private) about the none dedicated circuits? his comments were "look, i'll do the drawings, you just do the installation and things will be fine"!!! a year later i was called by goldman-saks to a meeting to discuss "computer problems"??? they had spent large amounts of money repairing and replacing computer equipment since moving into this office? again, in attendance was their engineer and he had a set of plans. he asked me if we had provided dedicated circuits to the work stations?? i explained to all in attendance that the plans did not call for dedicated circuits... he denied it and showed them on "his" plans!!! yes--he had changed his plans and not the dates.... i had my "as built" drawings and rolled them out over his. i was hot!!! then i explained, while trying to keep my cool, how i had asked this "so called" engineer about the dedicated circuits at the job site meeting and what his comment was!!!
we had added pull strings on all the home runs in the original installation figuring they would have problems, which made the repair easy! we went in early in the morning and repowered large areas using extension cords under the floor allowing us to shutdown the permanent circuits for repulling.. this was paid for by the tenant.
this was a very large engineering group --- about three years later they went belly up---it was great news!!!
ps: it's good to keep those "as builts"!!
we had added pull strings on all the home runs in the original installation figuring they would have problems, which made the repair easy! we went in early in the morning and repowered large areas using extension cords under the floor allowing us to shutdown the permanent circuits for repulling.. this was paid for by the tenant.
this was a very large engineering group --- about three years later they went belly up---it was great news!!!
ps: it's good to keep those "as builts"!!
MAK
Senior Member
- Location
- Massachusetts-Boston
I recently had a problem with a couple computers that had some problems with the USB keyboard not working and would not reboot after a power failure. After removing the pc and trouble shooting it in our office I ended up convincing myself that it had to be a power problem at the customers site. Reinstalled at customers site and figure out that was not the problem.
The customer had replace a KVM (ps2) switch with a usb only switch which caused the problems. Swapped out the switch with a ps2 version and it worked fine.
I should have picked up on the problem earlier but the info the customer had provided was not exactly accurate.
The customer had replace a KVM (ps2) switch with a usb only switch which caused the problems. Swapped out the switch with a ps2 version and it worked fine.
I should have picked up on the problem earlier but the info the customer had provided was not exactly accurate.
- Location
- Massachusetts
charlie tuna said:
Charlie, how did MWBCs cause damage to the computers assuming they where correctly wired?
And if a common neutral does damage computers how does the addition of a panel board prevent this damage with the common neutral of the feeder?
charlie tuna
Senior Member
- Location
- Florida
ever heard of harmonics?? shared neutrals feeding computer equipment causes harmonic currents returning to the panel that do not cancel each other out like on normal loads. it's because the returning current is returning at a different frequency due to the switching in the computerized equipment's power supply. these harmonics are going to cause fluctuations in system voltages. every computer's instructions begin with the suggestion of installing it on a dedicated circuit.... if this common neutral was oversized enough the effects of harmonics would be lessened.
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