I'm helping a friend find a fault with a rather ancient intruder alarm (Melcom ST6500) which is intermittently faulty. I thought the fault might be with the lead-acid backup battery as the old one was almost defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that looks like a resistor has badly overheated. On removing it the legend on the PCB underneath looks like "l4.7R" but the dot and the R are indistinct. Is it a 14.7 ohm resistor? It might well be in the battery-charging circuit. At present its measured resistance is around 10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

--
Clive Page

On Tuesday, 10 July 2018 11:20:29 UTC+1, Clive Page wrote:

I'm helping a friend find a fault with a rather ancient intruder alarm (Melcom ST6500) which is intermittently faulty. I thought the fault might be with the lead-acid backup battery as the old one was almost defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that looks like a resistor has badly overheated. On removing it the legend on the PCB underneath looks like "l4.7R" but the dot and the R are indistinct. Is it a 14.7 ohm resistor? It might well be in the battery-charging circuit.. At present its measured resistance is around 10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4.7 is a standard value, 14.7 is not. So it's most likely 4.7 something. The rest can be worked out from the circuit, which you've not provided.

A lot of old gizmos with small lead acid batteries just used a resistor to control charging. Basic battery data would also help.


NT

On 10/07/2018 11:29, wrote:
4.7 is a standard value, 14.7 is not. So it's most likely 4.7 something. The rest can be worked out from the circuit, which you've not provided.

The battery is 12v 2.1 Ah but I don't have the circuit diagram (how many alarms come with them?). It's the spiral pattern on the resistor body which I didn't recognise, and the lack of colour coding doesn't help at all. I have a resistor in my junk collection of about 18 ohms, I might try that.

I suspect the battery had some cells fail and if this resistor was in series with the charging circuit it got hot and failed, so the battery then went totally dud. But that's only a guess.

A lot of old gizmos with small lead acid batteries just used a resistor to control charging. Basic battery data would also help.

Thanks for your help.


--
Clive Page

On 10/07/2018 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty.Â* I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated.Â* On removing it the legend
on the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be in the
battery-charging circuit.Â* At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

There doesn't seem to be anything visible on the device to indicate its
value. The spiral is to increase the effective length of the resistive
material (carbon film perhaps).

I think you will have to analyse the circuit to decide the correct
value. Could the legend on the PCB be 14.7K? That would be closer to the
measured value. It's possible that it wasn't the resistor's "fault" that
it overheated, so there could be something else wrong.

--
Max Demian

On Tue, 10 Jul 2018 11:35:51 +0100, Clive Page wrote:

The battery is 12v 2.1 Ah but I don't have the circuit diagram (how many
alarms come with them?).

Yes you do have the circuit diagram, it's just not on a bit of paper
and takes a little more effort to interpet.

It's the spiral pattern on the resistor body which I didn't recognise,
and the lack of colour coding doesn't help at all.

Spiral pattern is typical of high wattage resistors that have burn
off their paint and colour bands.

--
Cheers
Dave.

Max Demian wrote:
I think you will have to analyse the circuit to decide the correct
value. Could the legend on the PCB be 14.7K? That would be closer to the
measured value. It's possible that it wasn't the resistor's "fault" that
it overheated, so there could be something else wrong.

Let's say it's a 1W resistor (though it's probably a 3W or a 5W):
If the value was 10K, to develop 1W in the resistor we'd need:
P=V^2/R
sqrt(PR)=V
sqrt(1*10000) = V = 100V across it

So the question is: where does this sit in the circuit?

If there's a transformer and it's on the secondary side, it would seem very
unlikely it's ballpark 10K, because they could have used a much lower
wattage resistor for the voltage that might be across it. If you put 12V
across a 10K resistor it would only take 14mW.

If it's on the primary side, it's possibly an inefficient circuit that might
have roughly mains voltage across it for some reason, and 10-20K wouldn't be
impossible.

If it's a series resistor then it's much more likely to be a few ohms, with
a small voltage drop across it (either primary or secondary side).

Theo

On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty.Â* I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated.Â* On removing it the legend
on the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be in the
battery-charging circuit.Â* At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

My guess is that may be a 4.7ohm resistor. Google image search for 4.7
ohm wire wound resistor shows at least one item that looks similar -
without the burned-off coating of course.

Nick

On Tuesday, 10 July 2018 12:08:30 UTC+1, Nick Odell wrote:
On 10/07/18 11:20, Clive Page wrote:

I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty.Â* I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated.Â* On removing it the legend
on the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be in the
battery-charging circuit.Â* At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

My guess is that may be a 4.7ohm resistor. Google image search for 4.7
ohm wire wound resistor shows at least one item that looks similar -
without the burned-off coating of course.

Nick

all resistor values look similar!
The spiral track is cut in production to raise the resistance value.


2.1Ah at 0.1C is 0.2A. 0.2A through 4R7 is 1v 0.2W. So it may indeed be 4.7 ohms. However I'd look at the circuit to see if that makes sense, or whether it could be 47R. If the PCB marking is definitely 4.7R rather than 47R, then 4.7 ohm it is.

These resistors should be replaced with something of higher power rating, they can be a bit of a fire risk otherwise.


NT

In article ,
Clive Page writes:
I'm helping a friend find a fault with a rather ancient intruder alarm (Melcom ST6500) which is intermittently faulty. I thought the fault might be with the lead-acid backup battery as the old one was almost defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that looks like a resistor has badly overheated. On removing it the legend on the PCB underneath looks like "l4.7R" but the dot and the R are indistinct. Is it a 14.7 ohm resistor? It might well be in the battery-charging circuit. At present its measured resistance is around 10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

It's a metal oxide power resistor. Metal oxide is deposited on the
surface of a ceramic cylinder (or tube), and a spiral is cut in it
to set the resistance to the required value.

Have you measured the resistance of it? There might be nothing
wrong with it, even though the covering has fallen off. These
are quite robust.

My guess would be it's a crude current limiter for charging the
battery.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Tuesday, 10 July 2018 12:34:55 UTC+1, Andrew Gabriel wrote:
In article ,
Clive Page writes:
I'm helping a friend find a fault with a rather ancient intruder alarm (Melcom ST6500) which is intermittently faulty. I thought the fault might be with the lead-acid backup battery as the old one was almost defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that looks like a resistor has badly overheated. On removing it the legend on the PCB underneath looks like "l4.7R" but the dot and the R are indistinct. Is it a 14.7 ohm resistor? It might well be in the battery-charging circuit. At present its measured resistance is around 10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

It's a metal oxide power resistor. Metal oxide is deposited on the
surface of a ceramic cylinder (or tube), and a spiral is cut in it
to set the resistance to the required value.

Have you measured the resistance of it? There might be nothing
wrong with it, even though the covering has fallen off. These
are quite robust.

My guess would be it's a crude current limiter for charging the
battery.

carbon film's cheaper


NT

On Tuesday, 10 July 2018 12:31:39 UTC+1, wrote:
On Tuesday, 10 July 2018 12:08:30 UTC+1, Nick Odell wrote:
On 10/07/18 11:20, Clive Page wrote:

I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty.Â* I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated.Â* On removing it the legend
on the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be in the
battery-charging circuit.Â* At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

My guess is that may be a 4.7ohm resistor. Google image search for 4.7
ohm wire wound resistor shows at least one item that looks similar -
without the burned-off coating of course.

Nick

all resistor values look similar!

They have a pretty colour strips on them though to indicate their resistance, which isn't much use of course when the colours have been burnt off. :-)

The spiral track is cut in production to raise the resistance value.

Might be the ealier verion of one of these.
https://www.rapidonline.com/truohm-k...sistor-62-0240

I think it's likely to be 4.7 ohms if it were a larger battery it could be 0.47 ohms.

From the satate of it it must have been overrarted for quite some time perhaps the battery shorted or soemthing but even then 12V across 4.7 is 2.5 amps.

giving 2.5x12 = 30 watts that would be enough to a 3W resistor to make it look like your picture


2.1Ah at 0.1C is 0.2A. 0.2A through 4R7 is 1v 0.2W. So it may indeed be 4..7 ohms. However I'd look at the circuit to see if that makes sense, or whether it could be 47R. If the PCB marking is definitely 4.7R rather than 47R, then 4.7 ohm it is.

These resistors should be replaced with something of higher power rating, they can be a bit of a fire risk otherwise.

If there's space for it, you could have it raised above the board as the lenght of the one show is only 11mm the one I've shown is 16mm so it wouldn't sit well on the board.



NT

On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty.Â* I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated.Â* On removing it the legend
on the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be in the
battery-charging circuit.Â* At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W



--
Of what good are dead warriors? €¦ Warriors are those who desire battle
more than peace. Those who seek battle despite peace. Those who thump
their spears on the ground and talk of honor. Those who leap high the
battle dance and dream of glory €¦ The good of dead warriors, Mother, is
that they are dead.
Sheri S Tepper: The Awakeners.

On Tuesday, 10 July 2018 15:14:56 UTC+1, The Natural Philosopher wrote:
On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty.Â* I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated.Â* On removing it the legend
on the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be in the
battery-charging circuit.Â* At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

That is not a 1/4W resistor

On 10/07/2018 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty.Â* I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated.Â* On removing it the legend
on the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be in the
battery-charging circuit.Â* At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.


Looks like a thin film resistor that has been trimmed to value.
If it is then it may be a high tolerance resistor.

Does it actually read anything across a multimeter?

Is it in fact an inductor?
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Clive Page" wrote in message
...
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty. I thought the fault might
be with the lead-acid backup battery as the old one was almost defunct,
but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated. On removing it the legend on
the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct. Is it a 14.7 ohm resistor? It might well be in the
battery-charging circuit. At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

--
Clive Page

On 10/07/2018 17:22, Brian Gaff wrote:
Is it in fact an inductor?
Brian


Not intentionally.

"The Natural Philosopher" wrote in message
news
On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty. I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated. On removing it the legend on
the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct. Is it a 14.7 ohm resistor? It might well be in the
battery-charging circuit. At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

Thats not a 1/4W resistor.

On 10/07/18 19:44, Jeff wrote:


"The Natural Philosopher" wrote in message
news
On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder
alarm (Melcom ST6500) which is intermittently faulty.Â* I thought the
fault might be with the lead-acid backup battery as the old one was
almost defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something
that looks like a resistor has badly overheated.Â* On removing it the
legend on the PCB underneath looks like "l4.7R" but the dot and the R
are indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be in the
battery-charging circuit.Â* At present its measured resistance is
around 10k but it may well have burned out too much for this to be
reliable.

It's about 11 mm long, and instead of colour bands it has an odd
spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

Thats not a 1/4W resistor.

Looks bloody like one to me. Mind you the photo has no scale.


--
"If you dont read the news paper, you are un-informed. If you read the
news paper, you are mis-informed."

Mark Twain

Brian Gaff wrote

Is it in fact an inductor?

Nope, its clearly a power resistor.

"Clive Page" wrote in message
...
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty. I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated. On removing it the legend on
the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct. Is it a 14.7 ohm resistor? It might well be in the
battery-charging circuit. At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

--
Clive Page

On Wed, 11 Jul 2018 05:46:09 +1000, "Rod Speed"
wrote:

Brian Gaff wrote

Is it in fact an inductor?

Nope, its clearly a power resistor.

You great gormless wally Rodders. Is there no limit to your ignorance.

It's a carbon film resistor that has been "cooked". As it's carbon
film and the spiral is still black, it will most likely have retained
its original value. A quick prod with a DMM will enlighten.

Power resistors are made from metal, or in the case of RF dummy loads,
can be carbon, but certainly not cut in a spiral.

If you dont know what you are on about, why not just shut up Rodders??

AB




"Clive Page" wrote in message
...
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty. I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated. On removing it the legend on
the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct. Is it a 14.7 ohm resistor? It might well be in the
battery-charging circuit. At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

--
Clive Page

"The Natural Philosopher" wrote in message
news
On 10/07/18 19:44, Jeff wrote:


"The Natural Philosopher" wrote in message
news
On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty. I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated. On removing it the legend
on the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct. Is it a 14.7 ohm resistor? It might well be in the
battery-charging circuit. At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

Thats not a 1/4W resistor.

Looks bloody like one to me.

Then you need new glasses.

Mind you the photo has no scale.

The wire is good enough for that.

Archibald Tarquin Blenkinsopp wrote
Rod Speed wrote
Brian Gaff wrote

Is it in fact an inductor?

Nope, its clearly a power resistor.

You great gormless wally Rodders. Is there no limit to your ignorance.

We'll see...

It's a carbon film resistor that has been "cooked".

Still a power resistor, ****wit.

As it's carbon film and the spiral is still black, it will most likely
have
retained its original value. A quick prod with a DMM will enlighten.

Power resistors are made from metal,

Not necessarily.

or in the case of RF dummy loads, can
be carbon, but certainly not cut in a spiral.

If you dont know what you are on about,

I do thank and have been using those
since before you were even born thanks.

"Clive Page" wrote in message
...
I'm helping a friend find a fault with a rather ancient intruder alarm
(Melcom ST6500) which is intermittently faulty. I thought the fault
might be with the lead-acid backup battery as the old one was almost
defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something that
looks like a resistor has badly overheated. On removing it the legend
on
the PCB underneath looks like "l4.7R" but the dot and the R are
indistinct. Is it a 14.7 ohm resistor? It might well be in the
battery-charging circuit. At present its measured resistance is around
10k but it may well have burned out too much for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd spiral
pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

--
Clive Page

On Wed, 11 Jul 2018 07:18:40 +1000, cantankerous geezer Rot Speed blabbered,
again:

Nope, its clearly a power resistor.

You great gormless wally Rodders. Is there no limit to your ignorance.

We'll see...

We all ALREADY see what the matter is with you, Rot!

--
Sqwertz to Rot Speed:
"This is just a hunch, but I'm betting you're kinda an argumentative
asshole.
MID:

On Tue, 10 Jul 2018 11:35:51 +0100
Clive Page wrote:

It's the spiral pattern on the resistor body which I didn't recognise

That's what a thin film resistor looks like under the paint. It's like
a wire-wound resistor but it uses a ribbon of conductor instead of a
round wire.

On 10/07/18 22:01, Jeff wrote:


"The Natural Philosopher" wrote in message
news
On 10/07/18 19:44, Jeff wrote:


"The Natural Philosopher" wrote in message
news On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder
alarm (Melcom ST6500) which is intermittently faulty.Â* I thought
the fault might be with the lead-acid backup battery as the old one
was almost defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something
that looks like a resistor has badly overheated.Â* On removing it
the legend on the PCB underneath looks like "l4.7R" but the dot and
the R are indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be
in the battery-charging circuit.Â* At present its measured
resistance is around 10k but it may well have burned out too much
for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd
spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

Thats not a 1/4W resistor.

Looks bloody like one to me.

Then you need new glasses.

Mind you the photo has no scale.

The wire is good enough for that.

You are an asshole

https://images-na.ssl-images-amazon....L._SL1500_.jpg



--
Of what good are dead warriors? €¦ Warriors are those who desire battle
more than peace. Those who seek battle despite peace. Those who thump
their spears on the ground and talk of honor. Those who leap high the
battle dance and dream of glory €¦ The good of dead warriors, Mother, is
that they are dead.
Sheri S Tepper: The Awakeners.

"The Natural Philosopher" wrote in message
news
On 10/07/18 22:01, Jeff wrote:


"The Natural Philosopher" wrote in message
news
On 10/07/18 19:44, Jeff wrote:


"The Natural Philosopher" wrote in message
news On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder
alarm (Melcom ST6500) which is intermittently faulty. I thought the
fault might be with the lead-acid backup battery as the old one was
almost defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something
that looks like a resistor has badly overheated. On removing it the
legend on the PCB underneath looks like "l4.7R" but the dot and the R
are indistinct. Is it a 14.7 ohm resistor? It might well be in the
battery-charging circuit. At present its measured resistance is
around 10k but it may well have burned out too much for this to be
reliable.

It's about 11 mm long, and instead of colour bands it has an odd
spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

Thats not a 1/4W resistor.

Looks bloody like one to me.

Then you need new glasses.

Mind you the photo has no scale.

The wire is good enough for that.

You are an asshole

https://images-na.ssl-images-amazon....L._SL1500_.jpg

What a stunning line in rational argument you have there.

The original pic shows the resistor much thicker than the wire than yours
is.

"The Natural Philosopher" wrote in message
news
On 10/07/18 22:01, Jeff wrote:


"The Natural Philosopher" wrote in message
news
On 10/07/18 19:44, Jeff wrote:


"The Natural Philosopher" wrote in message
news On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder
alarm (Melcom ST6500) which is intermittently faulty. I thought the
fault might be with the lead-acid backup battery as the old one was
almost defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something
that looks like a resistor has badly overheated. On removing it the
legend on the PCB underneath looks like "l4.7R" but the dot and the R
are indistinct. Is it a 14.7 ohm resistor? It might well be in the
battery-charging circuit. At present its measured resistance is
around 10k but it may well have burned out too much for this to be
reliable.

It's about 11 mm long, and instead of colour bands it has an odd
spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

Thats not a 1/4W resistor.

Looks bloody like one to me.

Then you need new glasses.

Mind you the photo has no scale.

The wire is good enough for that.

You are an asshole

https://images-na.ssl-images-amazon....L._SL1500_.jpg

I meant the wire diameter, not its length.

On 11/07/18 04:25, Jeff wrote:


"The Natural Philosopher" wrote in message
news
On 10/07/18 22:01, Jeff wrote:


"The Natural Philosopher" wrote in message
news On 10/07/18 19:44, Jeff wrote:


"The Natural Philosopher" wrote in message
news On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder
alarm (Melcom ST6500) which is intermittently faulty.Â* I thought
the fault might be with the lead-acid backup battery as the old
one was almost defunct, but with a new battery the fault is still
there.

On opening the control box up I can see on the main PCB something
that looks like a resistor has badly overheated.Â* On removing it
the legend on the PCB underneath looks like "l4.7R" but the dot
and the R are indistinct.Â* Is it a 14.7 ohm resistor?Â* It might
well be in the battery-charging circuit.Â* At present its measured
resistance is around 10k but it may well have burned out too much
for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd
spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

Thats not a 1/4W resistor.

Looks bloody like one to me.

Then you need new glasses.

Mind you the photo has no scale.

The wire is good enough for that.

You are an asshole

https://images-na.ssl-images-amazon....L._SL1500_.jpg


What a stunning line in rational argument you have there.

The original pic shows the resistor much thicker than the wire than
yours is.

Well then the pictures are there for everyone to see and judge for
themselves and of course every manufacturer uses the SAME diameter of
wire, don't they...

Frankly, I have given my opinion, and I dont give a tuppeny **** what
you think.

Nor, I suspect, does anyone else.


--
Its easier to fool people than to convince them that they have been fooled.
Mark Twain

"The Natural Philosopher" wrote in message
news
On 11/07/18 04:25, Jeff wrote:


"The Natural Philosopher" wrote in message
news
On 10/07/18 22:01, Jeff wrote:


"The Natural Philosopher" wrote in message
news On 10/07/18 19:44, Jeff wrote:


"The Natural Philosopher" wrote in message
news On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder
alarm (Melcom ST6500) which is intermittently faulty. I thought
the fault might be with the lead-acid backup battery as the old one
was almost defunct, but with a new battery the fault is still
there.

On opening the control box up I can see on the main PCB something
that looks like a resistor has badly overheated. On removing it
the legend on the PCB underneath looks like "l4.7R" but the dot and
the R are indistinct. Is it a 14.7 ohm resistor? It might well be
in the battery-charging circuit. At present its measured
resistance is around 10k but it may well have burned out too much
for this to be reliable.

It's about 11 mm long, and instead of colour bands it has an odd
spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

Thats not a 1/4W resistor.

Looks bloody like one to me.

Then you need new glasses.

Mind you the photo has no scale.

The wire is good enough for that.

You are an asshole

https://images-na.ssl-images-amazon....L._SL1500_.jpg

What a stunning line in rational argument you have there.

The original pic shows the resistor much thicker than the wire than yours
is.

Well then the pictures are there for everyone to see and judge for
themselves

They are indeed.

and of course every manufacturer uses the SAME diameter of
wire, don't they...

They dont vary enough to matter when all you want is some idea of the
scale. Even just those end caps show that its not a 1/4W resistor.

On Tuesday, 10 July 2018 20:06:52 UTC+1, The Natural Philosopher wrote:
On 10/07/18 19:44, Jeff wrote:


"The Natural Philosopher" wrote in message
news
On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder
alarm (Melcom ST6500) which is intermittently faulty.Â* I thought the
fault might be with the lead-acid backup battery as the old one was
almost defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something
that looks like a resistor has badly overheated.Â* On removing it the
legend on the PCB underneath looks like "l4.7R" but the dot and the R
are indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be in the
battery-charging circuit.Â* At present its measured resistance is
around 10k but it may well have burned out too much for this to be
reliable.

It's about 11 mm long, and instead of colour bands it has an odd
spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

Thats not a 1/4W resistor.

Looks bloody like one to me. Mind you the photo has no scale.


The photo doesn't but in the text is states the resistor is 11mm.
My 1/4 W resistors are about 6mm long and 2mm in diameter.

The 3W resistor I quoted was 16mm long, so I'm guess it was about 1-2 watts in it;s original form.

On Wednesday, 11 July 2018 11:25:40 UTC+1, whisky-dave wrote:
On Tuesday, 10 July 2018 20:06:52 UTC+1, The Natural Philosopher wrote:
On 10/07/18 19:44, Jeff wrote:
"The Natural Philosopher" wrote in message
news On 10/07/18 11:20, Clive Page wrote:
I'm helping a friend find a fault with a rather ancient intruder
alarm (Melcom ST6500) which is intermittently faulty.Â* I thought the
fault might be with the lead-acid backup battery as the old one was
almost defunct, but with a new battery the fault is still there.

On opening the control box up I can see on the main PCB something
that looks like a resistor has badly overheated.Â* On removing it the
legend on the PCB underneath looks like "l4.7R" but the dot and the R
are indistinct.Â* Is it a 14.7 ohm resistor?Â* It might well be in the
battery-charging circuit.Â* At present its measured resistance is
around 10k but it may well have burned out too much for this to be
reliable.

It's about 11 mm long, and instead of colour bands it has an odd
spiral pattern:
https://photos.app.goo.gl/QUrYiABWSeXHwR947

Thanks in advance for any help.

4R7 - 4.7 ohms 1/4 W

Thats not a 1/4W resistor.

Looks bloody like one to me. Mind you the photo has no scale.


The photo doesn't but in the text is states the resistor is 11mm.
My 1/4 W resistors are about 6mm long and 2mm in diameter.

The 3W resistor I quoted was 16mm long, so I'm guess it was about 1-2 watts in it;s original form.

agree. I'd fit a 5 watter.


NT

On 11/07/2018 11:25, whisky-dave wrote:

The photo doesn't but in the text is states the resistor is 11mm.
My 1/4 W resistors are about 6mm long and 2mm in diameter.

The 3W resistor I quoted was 16mm long, so I'm guess it was about 1-2 watts in it;s original form.

Thanks to all who responded. That's my guess as well, I think the initial digit "1" on the PCB might have been to denote this as a 1 watt resistor, and the 4.7 the resistance in ohms. I didn't recognise the original appearance because I guess the colour bands had burned off, and I'd never seen a naked resistor before. It's a surprise how long one can live before this happens. :-)


--
Clive Page

In article , Clive Page
scribeth thus
On 11/07/2018 11:25, whisky-dave wrote:

The photo doesn't but in the text is states the resistor is 11mm.
My 1/4 W resistors are about 6mm long and 2mm in diameter.

The 3W resistor I quoted was 16mm long, so I'm guess it was about 1-2 watts in
it;s original form.

Thanks to all who responded. That's my guess as well, I think the initial digit
"1" on the PCB might have been to denote this as a 1 watt resistor, and the 4.7
the resistance in ohms. I didn't recognise the original appearance because I
guess the colour bands had burned off, and I'd never seen a naked resistor
before. It's a surprise how long one can live before this happens. :-)



Why not send a close up pic of the location where the resistor came
from?..
--
Tony Sayer