continuity test pass, but lamp does not go on!

[interuser@hotmail.com]

A quite simple question to you guys, but it beats me:

I have a lamp in which I left the 2 AA batteries for quite some time.
As you know, the green stuff accumulated on the metal parts of the
lamp. By metal parts I mean the metals which come in contact to the
batteries in order to close the circuit. I scraped the green stuff off
and replaced the batteries but the lamp does not go on. I tested the
light bulb on another lamp and it works. I tested the metal parts for
continuity using a continuity tester and there is connectivity from
any metal part to any other when the lamp is in and the switch is on.
The batteries are new. However when the batteries are in and the
switch is on, the lamp does not go on. What is wrong? Did leaving the
old batteries for so long affected the connectivity of the metals
somehow ? Maybe increased their resistance?

Of course I could simply buy a new lamp, but my question here is
mostly educational.

Thanx

 

[Bill]

<interuser@hotmail.com> wrote in message
news:a840cbfe.0404221214.3ee9617b@posting.google.com...

A quite simple question to you guys, but it beats me:

I have a lamp in which I left the 2 AA batteries for quite some time.
As you know, the green stuff accumulated on the metal parts of the
lamp. By metal parts I mean the metals which come in contact to the
batteries in order to close the circuit. I scraped the green stuff off
and replaced the batteries but the lamp does not go on. I tested the
light bulb on another lamp and it works. I tested the metal parts for
continuity using a continuity tester and there is connectivity from
any metal part to any other when the lamp is in and the switch is on.
The batteries are new. However when the batteries are in and the
switch is on, the lamp does not go on. What is wrong? Did leaving the
old batteries for so long affected the connectivity of the metals
somehow ? Maybe increased their resistance?

Of course I could simply buy a new lamp, but my question here is
mostly educational.

Thanx

Obviously, I can't be sure but two things I would look at are 1. If there is a
back plate where the batteries connect to each other check that. 2 Whether
putting the batteries in causes more pressure against the metal plates, thus
moving them, causing a loss of connection. You could also double check the new
batteries in numerous ways.

Incidently, I sometimes use a metal file to clean things off in similar
situations - i.e. where you placed your continuity checker and where the
batteries touch may not be the same.

Bill

 

[John Fields]

On 22 Apr 2004 13:14:01 -0700, interuser@hotmail.com
(interuser@hotmail.com) wrote:

A quite simple question to you guys, but it beats me:

I have a lamp in which I left the 2 AA batteries for quite some time.
As you know, the green stuff accumulated on the metal parts of the
lamp. By metal parts I mean the metals which come in contact to the
batteries in order to close the circuit. I scraped the green stuff off
and replaced the batteries but the lamp does not go on. I tested the
light bulb on another lamp and it works. I tested the metal parts for
continuity using a continuity tester and there is connectivity from
any metal part to any other when the lamp is in and the switch is on.
The batteries are new. However when the batteries are in and the
switch is on, the lamp does not go on. What is wrong? Did leaving the
old batteries for so long affected the connectivity of the metals
somehow ? Maybe increased their resistance?

Of course I could simply buy a new lamp, but my question here is
mostly educational.

---
Did you but the batteries in both pointing in the same direction?^)

--
John Fields

 

[John Tserkezis]

Bill wrote:

Incidently, I sometimes use a metal file to clean things off in similar
situations - i.e. where you placed your continuity checker and where the
batteries touch may not be the same.

You would want to be careful with this. Battery terminals are usually coated
with nickel. filing this off would expose the copper (or whatever they chose
to use) underneath, allowing tarnish and further corrosion.

The "file" repair doesn't last very long.

Best to _try_ to clean off only the corrosion, but even sometimes this is not
possible, because the corrosion has gone through the nickel. I usually replace
in this instance (where possible).

I've tinned with solder, which tarnishes easily, but also cleans easily.
Sometimes just rolling the batteries in their case will scratch enough of the
tarnish off to reduce the resistance enough to make it work.
Not reliable enough for a customer repair though.

--
Linux Registered User # 302622 <http://counter.li.org>

 

[Ross Herbert]

On 22 Apr 2004 13:14:01 -0700, interuser@hotmail.com
(interuser@hotmail.com) wrote:

A quite simple question to you guys, but it beats me:

I have a lamp in which I left the 2 AA batteries for quite some time.
As you know, the green stuff accumulated on the metal parts of the
lamp. By metal parts I mean the metals which come in contact to the
batteries in order to close the circuit. I scraped the green stuff off
and replaced the batteries but the lamp does not go on. I tested the
light bulb on another lamp and it works. I tested the metal parts for
continuity using a continuity tester and there is connectivity from
any metal part to any other when the lamp is in and the switch is on.
The batteries are new. However when the batteries are in and the
switch is on, the lamp does not go on. What is wrong? Did leaving the
old batteries for so long affected the connectivity of the metals
somehow ? Maybe increased their resistance?

Of course I could simply buy a new lamp, but my question here is
mostly educational.

Thanx

Put the batteries in and leave the lamp out. Switch on and see if you
can measure the full battery voltage at the contacts which normally
connect to the lamp. If you can see the full voltage with the switch
on then make sure it disappears when you switch off. This proves the
switch works. If this checks ok then the only possibility is that the
torch contacts are not making firmly enough with the lamp contacts or
the lamp filament is intermittent open circuit. Try gently tapping the
torch with the switch on to check this out. Also you might try this
tap test in the torch which showed the lamp to be ok.

 

[Stan]

interuser@hotmail.com (interuser@hotmail.com) wrote:

}A quite simple question to you guys, but it beats me:
}
}I have a lamp in which I left the 2 AA batteries for quite some time.
}As you know, the green stuff accumulated on the metal parts of the
}lamp. By metal parts I mean the metals which come in contact to the
}batteries in order to close the circuit. I scraped the green stuff off
}and replaced the batteries but the lamp does not go on. I tested the
}light bulb on another lamp and it works.

I would be suspicious of the switch (having first checked the batteries
to see if I installed them correctly, + to -).

Describe the switch as best you can.

Stan.

 

[JR North]

There are sometimes riveted connections in the strips that
complete the power path. You may have overlooked these in
cleaning the unit. They may pass voltage, but little or no
current.
JR

"interuser@hotmail.com" wrote:

A quite simple question to you guys, but it beats me:

I have a lamp in which I left the 2 AA batteries for quite some time.
As you know, the green stuff accumulated on the metal parts of the
lamp. By metal parts I mean the metals which come in contact to the
batteries in order to close the circuit. I scraped the green stuff off
and replaced the batteries but the lamp does not go on. I tested the
light bulb on another lamp and it works. I tested the metal parts for
continuity using a continuity tester and there is connectivity from
any metal part to any other when the lamp is in and the switch is on.
The batteries are new. However when the batteries are in and the
switch is on, the lamp does not go on. What is wrong? Did leaving the
old batteries for so long affected the connectivity of the metals
somehow ? Maybe increased their resistance?

Of course I could simply buy a new lamp, but my question here is
mostly educational.

Thanx

--
Remove X to reply

--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth

 

[Michael]

"interuser@hotmail.com" wrote:

A quite simple question to you guys, but it beats me:

I have a lamp in which I left the 2 AA batteries for quite some time.
As you know, the green stuff accumulated on the metal parts of the
lamp. By metal parts I mean the metals which come in contact to the
batteries in order to close the circuit. I scraped the green stuff off
and replaced the batteries but the lamp does not go on. I tested the
light bulb on another lamp and it works. I tested the metal parts for
continuity using a continuity tester and there is connectivity from
any metal part to any other when the lamp is in and the switch is on.
The batteries are new. However when the batteries are in and the
switch is on, the lamp does not go on. What is wrong? Did leaving the
old batteries for so long affected the connectivity of the metals
somehow ? Maybe increased their resistance?

Of course I could simply buy a new lamp, but my question here is
mostly educational.

Thanx

I faced with the same problem several days ago. Very old (30+ years)
2-cell flashlight made for US military. Since it had belonged to my dad
so I was tempted to keep it. Batteries good; bulb good; spring at
bottom (v-) clean; metal bulb housing clean. But no flash to this
light! Turned out it had the old slide-contact type of switch and those
contacts were oxidized (no continuity). I tossed the silly thing.