I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

I think what I have to do is connect the probes of my multimeter to the
wires. If I get a reading of +9V then the wire connected to the red
probe is live?
Can someone confirm this?

Thanks.

wrote:
I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

I think what I have to do is connect the probes of my multimeter to the
wires. If I get a reading of +9V then the wire connected to the red
probe is live?
Can someone confirm this?


Yes, this is correct. Make sure the multimeter is set to Volts, and to a
range 20V +. It will likely read higher than 9V (if it is unregulated).
This is perfectly ok.


--
Grunff

wrote in message
ups.com...
I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

I think what I have to do is connect the probes of my multimeter to the
wires. If I get a reading of +9V then the wire connected to the red
probe is live?
Can someone confirm this?

Thanks.

Some devices have plugs wired the opposite way so that the outer sleeve is
positive.

If you have not already cut it off try your multimeter on that, positive
probe in the middle and ground to the outside. if you get +9v or above you
are correct.

You are correct with measuring the polarity of the wires.

Paul

Paul-S8 wrote:
wrote in message
ups.com...
I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

I think what I have to do is connect the probes of my multimeter to the
wires. If I get a reading of +9V then the wire connected to the red
probe is live?
Can someone confirm this?

Thanks.

Some devices have plugs wired the opposite way so that the outer sleeve is
positive.

If you have not already cut it off try your multimeter on that, positive
probe in the middle and ground to the outside. if you get +9v or above you
are correct.

You are correct with measuring the polarity of the wires.

Paul

Unfortunately I already cut the plug off.
If I do get the polarity wrong, is this likely to break the device?

wrote:
Paul-S8 wrote:
wrote in message
ups.com...
I have a baby monitor which is powered by a 9V mains transformer.
The cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that
the outer sleeve of the plug is earth, and the inner part is for
live. Problem is, I don't know which is which for the two wires in
the cable.

I think what I have to do is connect the probes of my multimeter to
the wires. If I get a reading of +9V then the wire connected to the
red probe is live?
Can someone confirm this?

Thanks.

Some devices have plugs wired the opposite way so that the outer
sleeve is positive.

If you have not already cut it off try your multimeter on that,
positive probe in the middle and ground to the outside. if you get
+9v or above you are correct.

You are correct with measuring the polarity of the wires.

Paul

Unfortunately I already cut the plug off.
If I do get the polarity wrong, is this likely to break the device?

Possibly?

Look at the device where the plug fits into it, usually there is an
indication as to where the polarity is. ie center + outer - or reverse of
this?
--
Sir Benjamin Middlethwaite

said the following on 13/02/2006 13:25:
Paul-S8 wrote:

You are correct with measuring the polarity of the wires.

Paul

Unfortunately I already cut the plug off.
If I do get the polarity wrong, is this likely to break the device?


Maybe, depending whether the baby monitor is reverse polarity protected.

If you still have the old plug (and you have left a bit of wire on it),
if you look closely, you may find that one of the wires has a small
ridge running down the edge or that there is printing on one wire only.
This will allow you to identify how the plug was connected using the
continuity test function of you multimeter.

HTH

In article . com,
wrote:
I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

I think what I have to do is connect the probes of my multimeter to the
wires. If I get a reading of +9V then the wire connected to the red
probe is live?
Can someone confirm this?

Unfortunately it could be either positive or negative tip on the plug -
although positive is more common.

And wrong connection could wreck the device. If you can get inside it
easily it should be possible to determine which it is - look for a large
capacitor which should give the ground polarity.

--
*If I worked as much as others, I would do as little as they *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article . com,
wrote:
I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

I think what I have to do is connect the probes of my multimeter to the
wires. If I get a reading of +9V then the wire connected to the red
probe is live?
Can someone confirm this?

Unfortunately it could be either positive or negative tip on the plug -
although positive is more common.

And wrong connection could wreck the device. If you can get inside it
easily it should be possible to determine which it is - look for a large
capacitor which should give the ground polarity.


Thanks, but there is simply no way I will be allowed to take this thing
apart
The other option I considered was to purchase one of these
off-the-shelf multi-voltage power transformers. But I'm even more
uncertain if this will work, or even damage the monitor, as they appear
to be 100 mA or above. Whereas the monitor's transformer is 10mA. I'm
guessing this is significant, but I could be wrong?

On Mon, 13 Feb 2006 13:57:55 +0000, Rumble .@. wrote:

said the following on 13/02/2006 13:25:
Paul-S8 wrote:

You are correct with measuring the polarity of the wires.

Paul

Unfortunately I already cut the plug off.
If I do get the polarity wrong, is this likely to break the device?


Maybe, depending whether the baby monitor is reverse polarity protected.

If you still have the old plug (and you have left a bit of wire on it),
if you look closely, you may find that one of the wires has a small
ridge running down the edge or that there is printing on one wire only.
This will allow you to identify how the plug was connected using the
continuity test function of you multimeter.

HTH

Yes - leads like these almost always have some sort of polarity marking on the cable - either a
stripe or ridge is common, but I have seen cable where one conductor was tinned-copper, the other
bare copper.

wrote:
Dave Plowman (News) wrote:
In article . com,
wrote:
I have a baby monitor which is powered by a 9V mains transformer.
The cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that
the outer sleeve of the plug is earth, and the inner part is for
live. Problem is, I don't know which is which for the two wires in
the cable.

I think what I have to do is connect the probes of my multimeter to
the wires. If I get a reading of +9V then the wire connected to the
red probe is live?
Can someone confirm this?

Unfortunately it could be either positive or negative tip on the
plug - although positive is more common.

And wrong connection could wreck the device. If you can get inside it
easily it should be possible to determine which it is - look for a
large capacitor which should give the ground polarity.


Thanks, but there is simply no way I will be allowed to take this
thing apart
The other option I considered was to purchase one of these
off-the-shelf multi-voltage power transformers. But I'm even more
uncertain if this will work, or even damage the monitor, as they
appear to be 100 mA or above. Whereas the monitor's transformer is
10mA. I'm guessing this is significant, but I could be wrong?

Thats fine, the supply will only draw the current it needs.
--
Sir Benjamin Middlethwaite

wrote:

I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

1] Look at the power supply unit. It will tell you the voltage and
current output and as a bonus it will tell you how the plug is
polarised, by means of a little diagram.

2] Write this down on a piece of paper.

3] Go to a high-street electrical retailer and buy a replacement power
supply unit with the same information on it. Less than £10 should do
it. Argos also sell them.

4] Plug it in to your monitor, plug it in to the mains, and that's it.

5] This is a baby monitor, you need to be assured it is working and
reliable. If you don't have the expertise to know what to do, don't do
it for this critical application.

6] HTH

Kate wrote:
wrote:

I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

1] Look at the power supply unit. It will tell you the voltage and
current output and as a bonus it will tell you how the plug is
polarised, by means of a little diagram.

2] Write this down on a piece of paper.

3] Go to a high-street electrical retailer and buy a replacement power
supply unit with the same information on it. Less than £10 should do
it. Argos also sell them.

4] Plug it in to your monitor, plug it in to the mains, and that's it.

5] This is a baby monitor, you need to be assured it is working and
reliable. If you don't have the expertise to know what to do, don't do
it for this critical application.

6] HTH

Thanks, but there's no need for the patronising tone. I'm not a total
retard.

Dave Plowman (News) wrote:
In article . com,
wrote:
I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that
the outer sleeve of the plug is earth, and the inner part is for
live. Problem is, I don't know which is which for the two wires in
the cable.

I think what I have to do is connect the probes of my multimeter to
the wires. If I get a reading of +9V then the wire connected to the
red probe is live?
Can someone confirm this?

Unfortunately it could be either positive or negative tip on the plug
- although positive is more common.

And wrong connection could wreck the device. If you can get inside it
easily it should be possible to determine which it is - look for a
large capacitor which should give the ground polarity.

Every device I've seen has a symbol near the input socket to indicate the
polarity; go to Google, click on Images and do a search for 'power symbol
centre positive'. This gives two pictures; one for centre positive and one
centre negative. Have a close look at your device and see if you can locate
the symbol. Connect the new plug appropriately to the wires as identified by
the procedure you described earlier.

Dave

wrote in message
oups.com...

1] Look at the power supply unit. It will tell you the voltage and
current output and as a bonus it will tell you how the plug is
polarised, by means of a little diagram.

2] Write this down on a piece of paper.

3] Go to a high-street electrical retailer and buy a replacement power
supply unit with the same information on it. Less than £10 should do
it. Argos also sell them.

4] Plug it in to your monitor, plug it in to the mains, and that's it.

5] This is a baby monitor, you need to be assured it is working and
reliable. If you don't have the expertise to know what to do, don't do
it for this critical application.

6] HTH

Thanks, but there's no need for the patronising tone. I'm not a total
retard.

The fact you use the words "Live and Earth" not Positive and Negative
The fact you cut off the plug before testing
The fact you didn't tell us the make model (Someone may have the same unit,
or may have a manual for it,
The fact you have to ask how you use your meter makes me think you should
retract that comment.

Kate was just trying to help here as far as I can see, especially with point
5 here (as you don't appear to be very competent in this field)

Ask for help, but please don't flame people if they answer the question,
even if you feel they have over explained or simplified something.

Shall we start again here?

Make:
Model:
Voltage on adaptor: 9v
Current on adaptor: 10mA
AC or DC on the output side (It will be AC on the input of course)
(AC will have a symbol like this ~ (That's a wavy line if it does not
display correctly on here)
DC will have a solid line with a broken line under it

If it an AC output, the polarity will not matter

Normally, you will see a symbol like this
http://www.voltaicsystems.com/images/symbol.gif
On either the adaptor or the device - do you have one?

Sparks...

wrote:
Kate wrote:
wrote:

I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

Whether you get a new plug on yours or a new wall wart makes no
difference from the point of view of getting the polarity correct. Same
problem either way.

Where it does make a difference is reliability if and only if you cant
solder. If you can, fine, but if you cant then I'd go with Kate and get
one ready made. Unsoldered dc pwoer plugs are just not reliable.

Either way you need to know the polarity for the unit, plugging it in
and hoping is 40% likely to kill it. There is almost always a little
diagram either on the wallwart or by the socket on the appliance,
usually in raised plastic with no ink, so you have to hold it to the
light to see it. If for any reason theres no marking, open it and see
which wire goes to the + and - on the big capacitor. Opening it is far
more likely to result in a working unit than guessing.

Fitting a new plug means there no voltage selector and polarity
selector switches to get moved to the wrong place, with unit either not
working or frying... so maybe diy is safer after all.


NT

In article ,
Dave wrote:
Every device I've seen has a symbol near the input socket to indicate
the polarity

Not in my experience; the wall wart is more likely to be marked - but not
always.

--
*No word in the English language rhymes with month, orange, silver,purple

Dave Plowman London SW
To e-mail, change noise into sound.

wrote in
oups.com:

Kate wrote:
wrote:

I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

I think it is most unlikely you will break the device by connecting it the
wrong way round, with something not hugely greater than the marked voltage
- in any case, if all else fails this is your only option and it's a 50/50
shot.

But I've had to do this so many times with unknown equipment, of most
cheapnesses, and always got away with it, that I've become pretty blase,
and tend to try it istead of thinking about it.

So good luck, and I don't wish to hear from your lawyers,

--


mike

Sparks wrote:

The fact you use the words "Live and Earth" not Positive and Negative
The fact you cut off the plug before testing
The fact you didn't tell us the make model (Someone may have the same unit,
or may have a manual for it,
The fact you have to ask how you use your meter makes me think you should
retract that comment.

Kate was just trying to help here as far as I can see, especially with point
5 here (as you don't appear to be very competent in this field)

Ask for help, but please don't flame people if they answer the question,
even if you feel they have over explained or simplified something.

Thanks for your kind words, Sparks.

Like you, I was worried that the OP has missed such obvious
information as is certainly avaliable on the power supply, and then
proceeded to ask how to use test equipment in order to find it out.

As I said, this is an application with some concerns: a failure of the
power supply or alarm leading to smoke release from compromised
circuit boards or plastic casings, and failure of the alarm at a
point when the baby is at risk are just two concerns.

I'm sorry my point-by-point suggestion didn't go down too well, but
this is a serious application that requires more of an input to put
right properly than the OP has so far demonstrated.

Kate wrote:


Thanks for your kind words, Sparks.

Like you, I was worried that the OP has missed such obvious
information as is certainly avaliable on the power supply, and then
proceeded to ask how to use test equipment in order to find it out.

As I said, this is an application with some concerns: a failure of the
power supply or alarm leading to smoke release from compromised
circuit boards or plastic casings, and failure of the alarm at a
point when the baby is at risk are just two concerns.

I'm sorry my point-by-point suggestion didn't go down too well, but
this is a serious application that requires more of an input to put
right properly than the OP has so far demonstrated.

My original posting was asking for confirmation that my understanding
was correct. Thanks to the helpful responses, I've now solved the
problem.
The reason I jumped on your post was that to me it did have a
patronising tone. I can't abide people taking this attitude, or
belittling others when they ask a reasonable question. You may have a
lot more knowledge on this subject than me, but we all have to start
somewhere. Yes maybe I did overlook the information on the power
supply, but I'm sure we have all missed the obvious at some time.
But I apologise if I misunderstood your post.

wrote:

Kate wrote:


Thanks for your kind words, Sparks.

Like you, I was worried that the OP has missed such obvious
information as is certainly avaliable on the power supply, and then
proceeded to ask how to use test equipment in order to find it out.

As I said, this is an application with some concerns: a failure of the
power supply or alarm leading to smoke release from compromised
circuit boards or plastic casings, and failure of the alarm at a
point when the baby is at risk are just two concerns.

I'm sorry my point-by-point suggestion didn't go down too well, but
this is a serious application that requires more of an input to put
right properly than the OP has so far demonstrated.

My original posting was asking for confirmation that my understanding
was correct. Thanks to the helpful responses, I've now solved the
problem.
The reason I jumped on your post was that to me it did have a
patronising tone. I can't abide people taking this attitude, or
belittling others when they ask a reasonable question. You may have a
lot more knowledge on this subject than me, but we all have to start
somewhere. Yes maybe I did overlook the information on the power
supply, but I'm sure we have all missed the obvious at some time.
But I apologise if I misunderstood your post.


Remember that the person answering your question has to start somewhere
too. If that happens to be below your exact level of knowledge, it
doesn't mean you were being patronised or belittled. It means that the
responder was being thoughtful, and had decided to err on the safe side.


--
Ian White

Ian White wrote:

Remember that the person answering your question has to start somewhere
too. If that happens to be below your exact level of knowledge, it
doesn't mean you were being patronised or belittled. It means that the
responder was being thoughtful, and had decided to err on the safe side.



Ok, but don't you think "write it down on a piece of paper" sounds like
something you'd say to a seven year old?

wrote:
Ian White wrote:

Remember that the person answering your question has to start
somewhere too. If that happens to be below your exact level of
knowledge, it doesn't mean you were being patronised or belittled.
It means that the responder was being thoughtful, and had decided to
err on the safe side.



Ok, but don't you think "write it down on a piece of paper" sounds
like something you'd say to a seven year old?

Not if you were saying it with good humour. Unfortunately you didn't appear
to read it with good humour. This is Usenet, you can't see the person
posting, and they can't see you - always a good idea to try to see if what
they are saying /could/ be seen to be good humoured before getting upset.
Have a nice day!

:-)

Dave

Dave wrote:
wrote:
Ian White wrote:

Remember that the person answering your question has to start
somewhere too. If that happens to be below your exact level of
knowledge, it doesn't mean you were being patronised or belittled.
It means that the responder was being thoughtful, and had decided to
err on the safe side.



Ok, but don't you think "write it down on a piece of paper" sounds
like something you'd say to a seven year old?

Not if you were saying it with good humour. Unfortunately you didn't appear
to read it with good humour. This is Usenet, you can't see the person
posting, and they can't see you - always a good idea to try to see if what
they are saying /could/ be seen to be good humoured before getting upset.
Have a nice day!

:-)


You too.
Suggestion that Kate should use smileys to convey humorous or sarcastic
comments, if that was intended.
Or am I stating the obvious? ;-)

"Dave" wrote in message
...
wrote:
Ian White wrote:

Remember that the person answering your question has to start
somewhere too. If that happens to be below your exact level of
knowledge, it doesn't mean you were being patronised or belittled.
It means that the responder was being thoughtful, and had decided
to
err on the safe side.



Ok, but don't you think "write it down on a piece of paper" sounds
like something you'd say to a seven year old?

Not if you were saying it with good humour. Unfortunately you didn't
appear
to read it with good humour. This is Usenet, you can't see the
person
posting, and they can't see you - always a good idea to try to see
if what
they are saying /could/ be seen to be good humoured before getting
upset.
Have a nice day!

:-)

Dave

Actually; 'writing it down on a piece of paper' and/or sketching
(plus nowadays taking digital photographs) of items being taken
apart is _standard_ practise for folk. It's amazing how frequently one
dismantles something then 're-mantles' it to find several 'bits left
over'.
A digital photo, that can then be discarded, is a useful accomplice
in repair work
Also folks at plumber's merchants; tool stores and places such as
Maplins are not fazed when someone profers a piece of paper
with the query 'Do you have something which is similar to this?',
they can consult their data sheets and sometimes suggest a
similar item - which may not be the _exact_ item you're attempting
to source.

--

Brian

On Tue, 14 Feb 2006 09:54:37 GMT, "Brian Sharrock"
wrote:


Actually; 'writing it down on a piece of paper' and/or sketching
(plus nowadays taking digital photographs) of items being taken
apart is _standard_ practise for folk.

nods

A digital photo, that can then be discarded, is a useful accomplice
in repair work

Wouldn't do much without mine nowdays. I've taken pictures of wheels
I'm about to re-spoke, laptops I'm taking to bits and it's been great
to be able to refer back to them "ahh, that went there"!

Also folks at plumber's merchants; tool stores and places such as
Maplins are not fazed when someone profers a piece of paper
with the query 'Do you have something which is similar to this?',

If I *don't* write down on a bit of paper what I need I forget what I
was after (by the end of the road these days) ..:-(

You would be surprised how often the "let's cover it step by step from
the beginning" process discovers summat really 'simple' that may have
been overlooked?

I did similar recently whilst trying to help someone (via e-mail)
setup a replacement wireless router. That *assumed* they could creat
the wireless network at the remote laptop (rather in the router).

It was the "Start internet explorer, replace the url with 192.168.0.1
and when connected enter the username and password. Click on Wireless
settings and enter your settings there" bit that gave them the bigger
picture .. ;-)

All the best ..

T i m

p.s. I was going to ask if this monitor system was a 'pair' in which
case there may have been an identical PSU on the remaining working
unit to check / measure?

wrote:

My original posting was asking for confirmation that my understanding
was correct. Thanks to the helpful responses, I've now solved the
problem.
The reason I jumped on your post was that to me it did have a
patronising tone. I can't abide people taking this attitude, or
belittling others when they ask a reasonable question. You may have a
lot more knowledge on this subject than me, but we all have to start
somewhere. Yes maybe I did overlook the information on the power
supply, but I'm sure we have all missed the obvious at some time.
But I apologise if I misunderstood your post.

Apology accepted. If my tone appeared patronising, I apologise for
that. It was done to avoid long-winded or over-complex replies, and to
avoid confusion.

I see from other posts that the suggestion to write the info on a
piece of paper wasn't received too well.

My thinking was that, if you were unfamiliar with voltages, currents,
and polarities, it's easy to get confused when looking at a pile of
power units in a shop. Having the hard info with you at that point
can be very useful!

Also, if you give the assistant the piece of paper and say "give me
one of these", than if he gives you the wrong one it's down to the
shop, not down to you.......'Nuff said, methinks ;-)

wrote:

Ian White wrote:

Remember that the person answering your question has to start somewhere
too. If that happens to be below your exact level of knowledge, it
doesn't mean you were being patronised or belittled. It means that the
responder was being thoughtful, and had decided to err on the safe side.



Ok, but don't you think "write it down on a piece of paper" sounds like
something you'd say to a seven year old?


I'd say it to anybody, whenever it's important to remember something in
complete and accurate detail.



--
Ian White

Kate wrote:
wrote:


Also, if you give the assistant the piece of paper and say "give me
one of these", than if he gives you the wrong one it's down to the
shop, not down to you.......'Nuff said, methinks ;-)

Wouldn't help if you go into my local Maplins. They seem to have even
less of a clue than I do.

On 14 Feb 2006 04:43:10 -0800,it is alleged that
spake thusly in uk.d-i-y:


Kate wrote:
wrote:


Also, if you give the assistant the piece of paper and say "give me
one of these", than if he gives you the wrong one it's down to the
shop, not down to you.......'Nuff said, methinks ;-)

Wouldn't help if you go into my local Maplins. They seem to have even
less of a clue than I do.

Sadly this is true, Maplin used to be run by clueful and helpful
people. Then they went all consumer electronics on us :-).

The suggestion to write down is a good one tho, I often fail to do it
myself LOL

--
You cannot shake hands with a clenched fist.
- Indira Gandhi

On Tue, 14 Feb 2006 13:46:54 GMT, Chip
wrote:

Sadly this is true, Maplin used to be run by clueful and helpful
people. Then they went all consumer electronics on us :-).

It seemed to happen all at once didn't it, like a corporate decision?

One day you went in and talked to Len who was into amateur radio and
computing, the next day it was in to talk to Tracey and explain to her
that a resistor wasn't someone who had fought off a rapist after
getting rat arsed down the pub last night.

wrote:
I have a baby monitor which is powered by a 9V mains transformer. The
cable has recently become unreliable, as I have to twist it at a
particular angle in order for the power to stay on.
I decided to replace the 2.5 mm plug on the end. I understand that the
outer sleeve of the plug is earth, and the inner part is for live.
Problem is, I don't know which is which for the two wires in the cable.

I think what I have to do is connect the probes of my multimeter to the
wires. If I get a reading of +9V then the wire connected to the red
probe is live?
Can someone confirm this?

In future.
With a very sharp knife, you can usually dissect the strain relief bit
of the cable.
Then, you (after noting polarity) cut off the insulation in the region
of where it needs twisted.
Cut both wires at that point, and anohter 1/2cm or so.
Solder the wire stubs together again, and add lots of insulation tape
pulled tightly round as strain relief.

Now, tape the baby monitor cord to the back of the baby monitor, so it
can't move.

Ian Stirling wrote:

In future.
With a very sharp knife, you can usually dissect the strain relief bit
of the cable.
Then, you (after noting polarity) cut off the insulation in the region
of where it needs twisted.
Cut both wires at that point, and anohter 1/2cm or so.
Solder the wire stubs together again, and add lots of insulation tape
pulled tightly round as strain relief.

Or arrange the two wires to leave a few mm air gap between the solder
joints, and then flood the whole thing with hot-melt glue.

It's probably stronger than anything you could manage with insulating
tape... but in any case:

Now, tape the baby monitor cord to the back of the baby monitor, so it
can't move.


--
Ian White