Got a plain Tesco phone which started a strange behaviour which I'm
wondering if anyone else has experienced before. It started ringing with
a continuous (i.e. no spaces between rings) whilst on-hook - my mum
thought a neighbour's car alarm had gone off! If the handset is lifted,
it functions as normally. If one of the other phones has its handset
lifted, the ringing on the faulty phone stops (until the other phone's
handset is back on-hook).
It's a 2 wire cable to the wall, so has its own "master socket" ring
generation circuitry. That plugs in underneath and appears as the red
and green wires in the middle on this pic:
http://tinypic.com/r/s2bjie/8
Or full size
http://oi57.tinypic.com/s2bjie.jpg
The handset plugs into the side of the base (Jamaican flag coloured wires).
No obvious dry joints on the board. Would it be the large red capacitor
or the large carbon film resistor at fault?
If it's a 20p fix I'll do it, otherwise the bin beckons!

On Friday, 3 April 2015 22:34:27 UTC+1, Part timer wrote:
Got a plain Tesco phone which started a strange behaviour which I'm
wondering if anyone else has experienced before. It started ringing with
a continuous (i.e. no spaces between rings) whilst on-hook - my mum
thought a neighbour's car alarm had gone off! If the handset is lifted,
it functions as normally. If one of the other phones has its handset
lifted, the ringing on the faulty phone stops (until the other phone's
handset is back on-hook).

This sounds consistent with the ringing capacitor failing short-circuit and passing DC to the ringing circuit; many electronic ringers will ring on DC.

When any handset is off-hook the DC line voltage falls to below a level which triggers the ringer.

If desoldering/opening one leg of the large red cap resolves the problem that's probably the cause; replace with a non-polarised capacitor of similar value or 2.2 uF if you don't know the value.

Owain

On 03/04/2015 22:55, wrote:
On Friday, 3 April 2015 22:34:27 UTC+1, Part timer wrote:
Got a plain Tesco phone which started a strange behaviour which I'm
wondering if anyone else has experienced before. It started ringing with
a continuous (i.e. no spaces between rings) whilst on-hook - my mum
thought a neighbour's car alarm had gone off! If the handset is lifted,
it functions as normally. If one of the other phones has its handset
lifted, the ringing on the faulty phone stops (until the other phone's
handset is back on-hook).

This sounds consistent with the ringing capacitor failing short-circuit and passing DC to the ringing circuit; many electronic ringers will ring on DC.

When any handset is off-hook the DC line voltage falls to below a level which triggers the ringer.

If desoldering/opening one leg of the large red cap resolves the problem that's probably the cause; replace with a non-polarised capacitor of similar value or 2.2 uF if you don't know the value.

Owain

Thanks for that! The red capacitor says CSD MER 105J250V - is it 1uF?
http://www.maplin.co.uk/p/metallised...apacitor-bx82d

Yes I've had this happen way back but in them days it looked a bit like a
large sweet with wires and coloured stripes. It got moissture in it where
the wires entered I think.
brian

--
From the Sofa of Brian Gaff Reply address is active
wrote in message
...
On Friday, 3 April 2015 22:34:27 UTC+1, Part timer wrote:
Got a plain Tesco phone which started a strange behaviour which I'm
wondering if anyone else has experienced before. It started ringing with
a continuous (i.e. no spaces between rings) whilst on-hook - my mum
thought a neighbour's car alarm had gone off! If the handset is lifted,
it functions as normally. If one of the other phones has its handset
lifted, the ringing on the faulty phone stops (until the other phone's
handset is back on-hook).

This sounds consistent with the ringing capacitor failing short-circuit
and passing DC to the ringing circuit; many electronic ringers will ring
on DC.

When any handset is off-hook the DC line voltage falls to below a level
which triggers the ringer.

If desoldering/opening one leg of the large red cap resolves the problem
that's probably the cause; replace with a non-polarised capacitor of
similar value or 2.2 uF if you don't know the value.

Owain

Have you had any lightening near you recently?
That can also upset these caps.

Brian

--
From the Sofa of Brian Gaff Reply address is active
"Part Timer" wrote in message
...
On 03/04/2015 22:55, wrote:
On Friday, 3 April 2015 22:34:27 UTC+1, Part timer wrote:
Got a plain Tesco phone which started a strange behaviour which I'm
wondering if anyone else has experienced before. It started ringing with
a continuous (i.e. no spaces between rings) whilst on-hook - my mum
thought a neighbour's car alarm had gone off! If the handset is lifted,
it functions as normally. If one of the other phones has its handset
lifted, the ringing on the faulty phone stops (until the other phone's
handset is back on-hook).

This sounds consistent with the ringing capacitor failing short-circuit
and passing DC to the ringing circuit; many electronic ringers will ring
on DC.

When any handset is off-hook the DC line voltage falls to below a level
which triggers the ringer.

If desoldering/opening one leg of the large red cap resolves the problem
that's probably the cause; replace with a non-polarised capacitor of
similar value or 2.2 uF if you don't know the value.

Owain

Thanks for that! The red capacitor says CSD MER 105J250V - is it 1uF?
http://www.maplin.co.uk/p/metallised...apacitor-bx82d

On Friday, April 3, 2015 at 11:20:50 PM UTC+1, Part timer wrote:
On 03/04/2015 22:55, wrote:
On Friday, 3 April 2015 22:34:27 UTC+1, Part timer wrote:
Got a plain Tesco phone which started a strange behaviour which I'm
wondering if anyone else has experienced before. It started ringing with
a continuous (i.e. no spaces between rings) whilst on-hook - my mum
thought a neighbour's car alarm had gone off! If the handset is lifted,
it functions as normally. If one of the other phones has its handset
lifted, the ringing on the faulty phone stops (until the other phone's
handset is back on-hook).

This sounds consistent with the ringing capacitor failing short-circuit and passing DC to the ringing circuit; many electronic ringers will ring on DC.

When any handset is off-hook the DC line voltage falls to below a level which triggers the ringer.

If desoldering/opening one leg of the large red cap resolves the problem that's probably the cause; replace with a non-polarised capacitor of similar value or 2.2 uF if you don't know the value.

Owain

Thanks for that! The red capacitor says CSD MER 105J250V - is it 1uF?
http://www.maplin.co.uk/p/metallised...apacitor-bx82d

yup


NT

On Fri, 3 Apr 2015 14:55:31 -0700 (PDT),
wrote:

Got a plain Tesco phone which started a strange behaviour which
I'm
wondering if anyone else has experienced before. It started
ringing
with a continuous (i.e. no spaces between rings) whilst on-hook

This sounds consistent with the ringing capacitor failing short-circuit

Or a A B wire swap between sockets. Check that every socket is wired
pin 1 to pin 1, pin 2 to 2 etc.

--
Cheers
Dave.

On Sunday, 5 April 2015 17:58:06 UTC+1, Dave Liquorice wrote:
Or a A B wire swap between sockets. Check that every socket is wired
pin 1 to pin 1, pin 2 to 2 etc.

In some circumstances, but not usually on a 2-wire phone.

Owain

On 05/04/2015 20:42, wrote:
On Sunday, 5 April 2015 17:58:06 UTC+1, Dave Liquorice wrote:
Or a A B wire swap between sockets. Check that every socket is wired
pin 1 to pin 1, pin 2 to 2 etc.

In some circumstances, but not usually on a 2-wire phone.

Owain

Dave, nothing else had changed when the cheap Tesco phone went on the
blink. I've done as Owain suggested in an earlier post and desoldered
the offending capacitor which cured the ringing problem when the phone
was plugged back in to test. It will be shelved pending obtaining
replacement cap.

James

On Sun, 05 Apr 2015 22:13:54 +0100, Part Timer wrote:

Or a A B wire swap between sockets. Check that every socket is
wired
pin 1 to pin 1, pin 2 to 2 etc.

In some circumstances, but not usually on a 2-wire phone.

I don't think we know if it is a two wire phone? Though most are
these days, unless it can pulse dial in which case it must pick up
the "bell wire" to supress bell tinkle when pulse dialling.

Dave, nothing else had changed when the cheap Tesco phone went on the
blink.

Didn't start to use a socket that wasn't being used before or shuffle
phones about when this new one arived?

I've done as Owain suggested in an earlier post and desoldered
the offending capacitor which cured the ringing problem when the phone
was plugged back in to test.

The capacitor is the network side of the demarcation point between
the network and your responsibilty. The test socket behind the lower
removeable plate of the NTE ("master socket") is the actual point.
Extension sockets your side of the demarcation point shouldn't have
the capacitor, resistor or spark gap.

--
Cheers
Dave.

On Monday, 6 April 2015 08:43:05 UTC+1, Dave Liquorice wrote:
In some circumstances, but not usually on a 2-wire phone.
I don't think we know if it is a two wire phone?

I think given by the information provided by the OP, including photographs, we have established that it is.

Owain

On 06/04/2015 11:35, Tim Streater wrote:
In article o.uk,
Dave Liquorice wrote:

On Sun, 05 Apr 2015 22:13:54 +0100, Part Timer wrote:

Or a A B wire swap between sockets. Check that every socket is
wired
pin 1 to pin 1, pin 2 to 2 etc.

In some circumstances, but not usually on a 2-wire phone.

I don't think we know if it is a two wire phone? Though most are
these days, unless it can pulse dial in which case it must pick up
the "bell wire" to supress bell tinkle when pulse dialling.

If you have a bell wire, get it removed if possible. It interferes with
broadband.

Note taken. I'll check the state of play and whether all the gear is two
wire. This cheap Tesco labelled phone _is_.

On 06/04/2015 08:32, Dave Liquorice wrote:
On Sun, 05 Apr 2015 22:13:54 +0100, Part Timer wrote:

Or a A B wire swap between sockets. Check that every socket is
wired
pin 1 to pin 1, pin 2 to 2 etc.

In some circumstances, but not usually on a 2-wire phone.

I don't think we know if it is a two wire phone? Though most are
these days, unless it can pulse dial in which case it must pick up
the "bell wire" to supress bell tinkle when pulse dialling.

Dave, nothing else had changed when the cheap Tesco phone went on the
blink.

Didn't start to use a socket that wasn't being used before or shuffle
phones about when this new one arived?

Nothing had changed for at least 6 months to a year, one day my mum had
heard this one phone go kaput as per my original post. She just happened
to mention it while I was visiting over Easter.

I've done as Owain suggested in an earlier post and desoldered
the offending capacitor which cured the ringing problem when the phone
was plugged back in to test.

The capacitor is the network side of the demarcation point between
the network and your responsibilty. The test socket behind the lower
removeable plate of the NTE ("master socket") is the actual point.
Extension sockets your side of the demarcation point shouldn't have
the capacitor, resistor or spark gap.

Understood. None of the extensions do (only one master socket
downstairs, not tampered with on this visit!) It's older than an NTE5
but that's not relevant here.
My original post related to the capacitor (found to be duff) and
resistor in the faulty two wire Tesco phone which I suppose are to help
the thing in ringing/not ringing as required.
Thanks anyway - I value all replies and know you have expertise in this.
Peter Parry's excellent site
http://www.wppltd.demon.co.uk/WPP/Wi...telephone.html
taught me much in 2001 when I first did some troubleshooting and
extensions, spurred on by an AS physics textbook briefly mentioning the
2 and 3 wires, R, C and spark gap.

On 03/04/2015 22:55, wrote:

This sounds consistent with the ringing capacitor failing short-circuit and passing DC to the ringing circuit; many electronic ringers will ring on DC.

When any handset is off-hook the DC line voltage falls to below a level which triggers the ringer.

If desoldering/opening one leg of the large red cap resolves the problem that's probably the cause; replace with a non-polarised capacitor of similar value or 2.2 uF if you don't know the value.

Owain

Phone is now fixed and back together. Long live uk.d-i-y and all the
advice people give so willingly.