challenge: outlet won't power computer/monitor


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Old 11-27-08, 12:51 PM
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challenge: outlet won't power computer/monitor

Hello,

Here's a good challenge.

I bought an old house which has some old knob and tube (with no ground) electrical outlets.

I temporarily replaced a 2 prong outlet with a 3 prong in order to plug in my PC and monitor. When I plug my computer (or monitor) in this outlet, the light on the power bar flashes steadily as well as the monitor which is plugged into this power bar. If I connect my DELL PC on it, it cycles on / off. where I hear the fan start, then stop, then start, then stop, on and on.

I checked and I'm registering 125 V. AC on the outlet. It will power up a radio no problem. If I plug same power bar in another outlet... the red light on the power bar is steady and the monitor works perfectly. I even tried reversing the wires on the plug... no diff.

strange eh?

How can I resolve this? any help will be appreciated.

Gilles
 
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Old 11-27-08, 01:25 PM
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First off installing the 3 prong outlet is not legal. The only way to be code compliant is to replace it with a GFCI outlet or some how get a ground wire to the outlet and ground it. Make sure you put the white on the silver screws and the black (or other color) on the brass screws.

With your other problem, have you tried putting a heavier load on that circuit like a hair dryer? Although a computer does not draw that much current it is more than just a radio and with the increased load, it may be causing a poor connection to rear it ugly head. You may have to remove more outlets to see if you can find the bad connection. Make sure all devices are not back stabbed and and all connections are tight.
 
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Old 11-27-08, 01:35 PM
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Thanks for your reply Tony.

I know about the legal stuff... it's just to tide me over until I redo the whole thing. In the meantime, I need to get my home office going.

Getting a ground wire to the outlet is not possible at this time. The room is on the 2nd story y of the house.

A bad connection can be causing what I'm seeing? even though lights which are on the same circuit (and radio, etc) work? Yes, I didn't think an LCD monitor drew that much current either.

What's strange is that as I mentioned, the light on the power bar blinks (very steadily) when the monitor is plugged into it as if it's meant to mean something. I looked on the net for a description of this symptom... nothing.

any other thoughts?
 
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Old 11-27-08, 01:48 PM
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I know you said you tried it on another outlet and it worked fine but, how about just skipping the power strip? Just plug into the wall no strip. The strip could be "freaking out" because there is no ground.

The bad connection could be after the lights so they would show no issues.

IS the blinking rhythmic or random?

Are you in the US and using equipment for the US power? (120 volt Hz?)
 
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Old 11-27-08, 01:53 PM
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Yes it's very rhythmic. If I by pass the power bar, The Dell monitor displays the Dell logo, on and off, in the same manner as the power bar LED. If I put the PC directly in the outlet, it tries to power up (fan starts), gives ups after about 2 seconeds (fan winds down), starts, stops in the same rhythmic manner.

Yes, US equipment in Canada.
 
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Old 11-27-08, 02:03 PM
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Let me repeat something Tolyn said:

have you tried putting a heavier load on that circuit like a hair dryer?
I think this is a good experiment. If you don't have a hair dryer, try a vacuum cleaner or a space heater.
 
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Old 11-27-08, 02:14 PM
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Running out of ideas.
Can you plug into a different outlet on the same circuit and have the same result? If so then it's the circuit issue. Can you plug into another circuit and get it to work? You strip isn't a battery back up system is it?
 
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Old 11-27-08, 02:20 PM
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Thanks for your time and patience fellows.

1. OK, I'll try a space heater. What am I looking for when I plug it in? (don't say smoke!! )

2. most of the house are newer circuits (grounded). I tried it on one downstairs which I don't think is grounded, although it has 3 prong receptacle (my tester reports ("open ground") and it works fine, no blinking.
 
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Old 11-27-08, 02:49 PM
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Originally Posted by gilles.gagnon View Post
Thanks for your time and patience fellows.

1. OK, I'll try a space heater. What am I looking for when I plug it in? (don't say smoke!! )

2. most of the house are newer circuits (grounded). I tried it on one downstairs which I don't think is grounded, although it has 3 prong receptacle (my tester reports ("open ground") and it works fine, no blinking.
Your looking for the same on-off issue

But does your computer equipment work on the non blinking outlet?
 
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Old 11-27-08, 02:58 PM
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yes, it works on other outlets. all other outlets don't cause the power bar's light to blink rhythmically (this is a simple power bar, not a UPS).
 
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Old 11-27-08, 03:12 PM
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Update

OK,

I plugged in an elec. heater and if it's on "fan" it works (setting number "0"). As soon as I turn the switch the the first heater setting or greater (setting number "1" ... it has 5 settings) ... it stops working.

WHat does this tell me?
 
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Old 11-27-08, 04:10 PM
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Somewhere on your circuit, you have a weak connection. It could be anywhere. Often is is a backstabbed connection (a wire poked into a hole). It is not difficult to fix it, but it can be quite time-consuming. It's a matter of opening up every box on the circuit and remaking the connections.

The danger with old wiring, however, is that the insulation may crumble as you handle it.

If you own this house, you should start saving up your money for a replacement of the electrical system. Old electrical systems cannot support modern lifestyles.
 
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Old 11-27-08, 07:20 PM
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Thanks for the tip John.

By the way, can you explain how a weak connection causes this behaviour?

Yes, I own the house. you're right, the old wiring sheathing is very brittle. I think I'll have to leave it alone and use an extension cord from another receptacle until I redo the electrical.

Not a great temporary solution as it crosses the doorway. The problem can be anywhere on the circuit.

Oh well... at least I know I wasn't going insane.
 
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Old 11-27-08, 07:31 PM
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This is just like an old outlet where you need to "giggle" the plug to get something to work. But that does not do the trick. Then you bend the prongs on the plug so it presses harder on the contacts inside the outlet, then it works.

(If this happens you should of course replace the outlet instead of bending the prongs...)

BTW - Excellent troubleshooting advice by everyone in this thread!
 
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Old 11-27-08, 07:49 PM
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Hi Bill190,

Thanks for your response but the problem is not what you described. As noted in thread, if I plug a radio in, it doesn't cut off, neither does a light. BUT.... the LCD computer monitor will rhytmically blink, the PC will rhythmically attempt to power up and the heater can be set to "fan only" mode but any other "heat" setting will cause it stop functioning.

so i don't think it's the same as a bad receptacle where jiggling causes the problem. As a matter of fact I installed a new outlet.

make sense?
 
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Old 11-27-08, 08:16 PM
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The problem is thermal. As current flows through the wire and connections, they heat up. As they heat up, they expand. Repeated expansions and contractions weaken the spring clips in backstab connections. The higher the current, the more the thermal differences. That is why low-current devices such as a radio may not cause the problem, while high-current devices such as a space heater do.

The problem cannot be found by mere visual inspection, since good and bad connections look visually similar.
 
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Old 11-28-08, 08:48 AM
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Originally Posted by gilles.gagnon View Post
Hi Bill190,

Thanks for your response but the problem is not what you described. As noted in thread, if I plug a radio in, it doesn't cut off, neither does a light. BUT.... the LCD computer monitor will rhytmically blink, the PC will rhythmically attempt to power up and the heater can be set to "fan only" mode but any other "heat" setting will cause it stop functioning.

so i don't think it's the same as a bad receptacle where jiggling causes the problem. As a matter of fact I installed a new outlet.

make sense?
I understand the outlet is not the problem. I was using that as an example of how a poor connection somewhere can cause these problems (without getting too technical).
 
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Old 11-28-08, 04:13 PM
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Originally Posted by Bill190 View Post
BTW - Excellent troubleshooting advice by everyone in this thread!

Thanks! You made my day!
 
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Old 11-28-08, 04:51 PM
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Update!

Hi Fellows,

I discovered something else on this circuit.

There is a porch with a ceiling light adjacent to the room with the "troublesome outlet". I suspect that the ceiling light (which has a switch on it), is connected in SERIES on the same circuit!!!! If I turn off the light, a radio plugged into the outlet goes off! This is Crazy!

1. COuld I be correct here and would this cause the symptoms I'm experiencing?
2. If so, is the correct way to rectify this to simply remove the light and connect it's two wires together?

Thanks again to everyone for their persistence in helping me solve this mystery.

G
 
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Old 11-28-08, 04:54 PM
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Yes, you could be correct. In fact, your theory is better than all of ours.

Here's a way to verify. Plug the radio in and turn it on. Turn the light on also. Do not turn off the light, but simply unscrew the bulb while the light is on.
 
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Old 11-28-08, 04:56 PM
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Hi Fellows,

I discovered something else on this circuit.

There is a porch with a ceiling light adjacent to the room with the "troublesome outlet". I suspect that the ceiling light (which has a switch on it), is connected in SERIES on the same circuit!!!! If I turn off the light, a radio plugged into the outlet goes off! This is Crazy!

1. COuld I be correct here and would this cause the symptoms I'm experiencing?
2. If so, is the correct way to rectify this to simply remove the light and connect it's two wires together?

Thanks again to everyone for their persistence in helping me solve this mystery.

G
 
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Old 11-28-08, 04:58 PM
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You could be correct again!!
 
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Old 11-28-08, 05:12 PM
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more info.

There is a wall switch above the outlet. If I turn it off, the radio on the outlet goes off AND the ceiling light for the porch goes ON. If I turn the wall switch off, the light goes off and the radio turns ON.

What the heck?
 
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Old 11-28-08, 05:33 PM
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Originally Posted by gilles.gagnon View Post
I even tried reversing the wires on the plug... no diff.
Do not reverse wires on plugs. If your computer is plugged in to non reversed outlet and printer is plugged into reversed outlet you will generate smoke from the back of your computer.

You have a brown out problem.
In normal practice knob and tube wiring splices are soldered
How to identify, inspect, evaluate, repair knob and tube electrical wiring
After umpteen years the lead/silver solder has crystallized and you have a big I squared R drop.

Get you expensive computer off that old wiring and at least rewire the one circuit for you computer and other expensive gear up to current code compliance.

Plug that hair dryer in then test the voltage it will be very low. No don't do that.
THAT SOLDER JOINT IS GETTING VERY HOT.

STOP-DO NOT DRAW CURRENT FROM THIS CIRCUIT, DISCONNECT EVERYTHING!!!!
YOU WILL START A FIRE AND BURN DOWN YOUR HOUSE IF YOU DO!!!!


You have got to rewire that house and use those electrical connections as little as possible. Where there is one bad solder splice there may be more.
 
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Old 11-28-08, 05:49 PM
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Thanks,

Wow, this really scares me!!! but how is the switch connected since in turns on the outlet and turns off the light simultaneously?

what's a "I squared R drop"?
 
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Old 11-28-08, 06:12 PM
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Originally Posted by gilles.gagnon View Post
Thanks,

Wow, this really scares me!!! but how is the switch connected since in turns on the outlet and turns off the light simultaneously?

what's a "I squared R drop"?
Funny, I just had a Uncle ask me this same question. ( warning long story)
He wanted a light at the top of the stairs going down into the basement. So he just wired it into the switch at the top of the stairs. Switch box had only 2 wires. He hooked one wire of the light to one each of the switch. When the switch was off the light at the top was on, basement lights were off. When the switch was on, the basement lights were on but the top light was off. What he did was wire the new light in series of a switch loop. There was no neutral. So with the switch off, current would flow through the top light but it wasn't enough to make the basement lights glow because of the voltage drop. With the switch on the current would flow to the basement lights but not enough current would flow tot he top light due to the resistance of the bulb.

I'm guessing since the light is on when you have the switch off, your light is wired in series of the switch loop, Causing your "brown out".

BTW - was there more than two or two sets of wires in the outlet box? Say like a black, white and a red?
 
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Old 11-28-08, 06:16 PM
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thanks so much for the explanation!

Can I rectify the problem by simply eliminating the light on the porch? (that is, removing the light socket and connecting the 2 wires together).
 
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Old 11-28-08, 06:28 PM
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Originally Posted by gilles.gagnon View Post
Thanks,

Wow, this really scares me!!! but how is the switch connected since in turns on the outlet and turns off the light simultaneously?

what's a "I squared R drop"?
It was meant to scare because it is dangerous. Most insurance companies will not cover the house with that kind of wiring. stop playing with that circuit and disconnect it from your fuse box. Study this
How to identify, inspect, evaluate, repair knob and tube electrical wiring

I squared R drop is a brownout (low voltage). That solder joint is like a toaster element. The greater the V drop across the solder joint for constant I that is P=I squared R = power in watts which is heat.

Introduction to DC Circuits
PhysicsLAB: An Introduction to DC Circuits
 
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Old 11-28-08, 06:53 PM
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I will be changing the wiring soon. Getting rid of the last of the knob and tube.

I understand the warning, however, assuming the old wiring is in good condition, can I not just remove the "in-line" light?
 
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Old 11-28-08, 08:33 PM
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Disconnect the light at the switch after you confirm that is what it is. It probably wired with bell wire or lamp cord anyway. =\
 
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Old 11-28-08, 09:04 PM
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I suggest you get a very knowledgeable person in to take a look. Once things are this screwed up, any assumptions we might make are likely to be wrong. You need some experienced eyes, and test instruments, on this problem. The danger of just trying random things is that you might get it to work---and create a latent hazard in the process. Not everything that works is safe.
 
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Old 11-29-08, 05:53 AM
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Originally Posted by focusonz View Post
Most insurance companies will not cover the house with that kind of wiring.
Are you saying that insurance companies won't cover a house with knob and tube wiring? If that's the case, half the houses in my city don't have insurance.
 
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Old 11-29-08, 06:56 AM
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indeed, the light is dangling from the ceiling with cord lamp.

I think I'll take John's advice and leave it as is. I'll be getting the house rewired anyhow. I thought of doing it myself but I think I'll splurge the $10,000. Although I'm handy and understand circuits to some degree I'm feeling a bit overwhelmed about rewiring.

The house (semi-detached) is plaster-lath construction and I don't know all the tricks of the trade to running wiring through existing walls. Also, 1/2 the roof is a flat room with limited attic access.

BTW, that is correct for our area (Toronto, Canada). When you purchase a house, as of a few years ago, insurance companies insist on havnig the old K&T replaced. they give you a few months to get that done.
 
 

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