There's probably a million and one things that could be wrong but I just
wondered if anyone could hazard a guess why my portable TV is dead. It's a
Grundig 15" cobi tv/vcr twin tuner which is around 10 years old, so may well
have died of old age. It was left recording but later noticed there was no
power or standby light. There's power from the plug going into the tv. Had
a look inside and noticed the main fuse had blown so replaced with identical
T1.6 from maplins. A continuity tester showed power was now flowing around
the circuits when switched on but still nothing happening on either the tv
or vcr. I'll probably scrap it but thought I'd ask just in case anyone
knows of any common problems with this model that may be worth having fixed?

Redwood wrote:
There's probably a million and one things that could be wrong but I just
wondered if anyone could hazard a guess why my portable TV is dead.

Go here.
http://www.highlandelectrix.fsnet.co.uk/repair/safety.html
http://www.repairfaq.org/samnew/tvfaq.htm

Or post same to sci.electronics.repair but quote the model number!!!

--
Adrian C

In an earlier contribution to this discussion,
Redwood wrote:

There's probably a million and one things that could be wrong but I
just wondered if anyone could hazard a guess why my portable TV is
dead. It's a Grundig 15" cobi tv/vcr twin tuner which is around 10
years old, so may well have died of old age. It was left recording
but later noticed there was no power or standby light. There's power
from the plug going into the tv. Had a look inside and noticed the
main fuse had blown so replaced with identical T1.6 from maplins. A
continuity tester showed power was now flowing around the circuits
when switched on but still nothing happening on either the tv or vcr.
I'll probably scrap it but thought I'd ask just in case anyone knows
of any common problems with this model that may be worth having
fixed?

I'm not quite sure what you mean about "power was now flowing around the
circuits" - do you simply mean that there was a finite resistance between
live and neutral, rather than an open circuit?

As a pure guess, something - maybe a diode or capacitor - in the internal
power supply has blown, causing the fuse to blow. Locating and replacing the
faulty component may well fix the problem. If you can do it yourself, it may
only cost a few pounds - but it may not be economical if you have to pay
someone else to do it.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

"Redwood" wrote in message
...
There's probably a million and one things that could be wrong but I just
wondered if anyone could hazard a guess why my portable TV is dead. It's
a
Grundig 15" cobi tv/vcr twin tuner which is around 10 years old, so may
well
have died of old age. It was left recording but later noticed there was
no
power or standby light. There's power from the plug going into the tv.
Had
a look inside and noticed the main fuse had blown so replaced with
identical
T1.6 from maplins. A continuity tester showed power was now flowing
around
the circuits when switched on but still nothing happening on either the tv
or vcr. I'll probably scrap it but thought I'd ask just in case anyone
knows of any common problems with this model that may be worth having
fixed?



Check the power supply PCB joints for any dry joints by using a tooth brush
dipped in meths and scrub over the area of the power supply,this will reveal
any dry joints ie the solder will go grey and if a dry joint is present
it'll show up as a dark/blac cracking or use a magnifier.

If you're not savvy with electronic stuff then bin it although it is a
TV/VCR these are worth more than the TV/DVD Combis.

"Roger Mills" wrote in message

but it may not be economical if you have to pay someone else to do it.

--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!



Ya got that right, I've ust been down to my local TV&Radio spares shop which
I have not been to for nigh on ten years and I knew the bloke very well.

I was disheartened when he told me he's closing down as his over heads is
crippling his profits because the electronic consumer goods repairing has
diminished considerably as no one wants to pay for the repairs of TV's
Video's,DVD's.. ect.

I blame it on todays throw away society.

George wrote:


Check the power supply PCB joints for any dry joints by using a tooth brush
dipped in meths and scrub over the area of the power supply,

How conductive is flammable meths applied over a rectified mains
recently charged reservoir capacitor? The latter should be safely
discharged before attempting this.

http://www.highlandelectrix.fsnet.co.uk/repair/safety.html

--
Adrian C

"Adrian C" wrote in message
...
George wrote:


Check the power supply PCB joints for any dry joints by using a tooth
brush
dipped in meths and scrub over the area of the power supply,

How conductive is flammable meths applied over a rectified mains
recently charged reservoir capacitor? The latter should be safely
discharged before attempting this.

http://www.highlandelectrix.fsnet.co.uk/repair/safety.html

--
Adrian C

Erm! I've been doing it for over 25 years and never had a fire yet nor a
short on TV's,the meths dry out very quickly.

On Apr 7, 11:58*am, "George" wrote:
"Roger Mills" wrote in message

*but it may not be economical if you have to pay someone else to do it.

--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Ya got that right, I've ust been down to my local TV&Radio spares shop which
I have not been to for nigh on ten years and I knew the bloke very well.

I was disheartened when he told me he's closing down as his over heads is
crippling his profits because the electronic consumer goods repairing has
diminished considerably

A bit like todays standards of literacy.

as no one wants to pay for the repairs of TV's
Video's,DVD's.. ect.

I blame it on todays throw away society.

I blame it on the parents.

"Man at B&Q" wrote in message

I blame it on the parents.

Yep,in your case they reared an asehole.

Ah didums, what did you fail at in scool?

On Apr 7, 12:56*pm, "George" wrote:
"Man at B&Q" wrote in message

I blame it on the parents.

Yep,in your case they reared an asehole.

Ah didums, what did you fail at in scool?

I rest my case.

"Man at B&Q" wrote in message
...
On Apr 7, 12:56 pm, "George" wrote:
"Man at B&Q" wrote in message

I blame it on the parents.

Yep,in your case they reared an asehole.

Ah didums, what did you fail at in scool?

I rest my case.

What ya mean School and Aw?

You can't even spell necessary,its spelt with one 'c' not two

On Apr 7, 1:04*pm, "George" wrote:
"Man at B&Q" wrote in ...
On Apr 7, 12:56 pm, "George" wrote:

"Man at B&Q" wrote in message

I blame it on the parents.

Yep,in your case they reared an asehole.

Ah didums, what did you fail at in scool?

I rest my case.

What ya mean School and Aw?

You can't even spell necessary,its spelt with one 'c' not two

And its should be it's

Stop digging!

"Man at B&Q" wrote in message
...
On Apr 7, 1:04 pm, "George" wrote:
"Man at B&Q" wrote in
.
...
On Apr 7, 12:56 pm, "George" wrote:

"Man at B&Q" wrote in message

I blame it on the parents.

Yep,in your case they reared an asehole.

Ah didums, what did you fail at in scool?

I rest my case.

What ya mean School and Aw?

You can't even spell necessary,its spelt with one 'c' not two

And its should be it's

Stop digging!

Stop being a pedant.

wrote in message ...
On 7 Apr,
"George" wrote:

Erm! I've been doing it for over 25 years and never had a fire yet nor a
short on TV's,the meths dry out very quickly.

I did have a fire once using 'cfc free' electrical spray cleaner. I was
using
it to clean a switch carrying only 28volts, when I noticed the flames.

--
B Thumbs
Change lycos to yahoo to reply

Reminds me of the time I was on the Manx ferries.

One of the deckhands was all set for a night out on the town.
Had a ciggy in his mouth and started spraying cossack hairspray on his
bonce,ended up with no eyebrows...that put paid to nights out for awhile.
;-)

On Apr 7, 1:19*pm, "George" wrote:
"Man at B&Q" wrote in ...
On Apr 7, 1:04 pm, "George" wrote: "Man at B&Q" wrote in

.
..

On Apr 7, 12:56 pm, "George" wrote:

"Man at B&Q" wrote in message

I blame it on the parents.

Yep,in your case they reared an asehole.

Ah didums, what did you fail at in scool?

I rest my case.

What ya mean School and Aw?

You can't even spell necessary,its spelt with one 'c' not two

And its should be it's

Stop digging!

Stop being a pedant.

Learn to quote correctly.

Roger Mills wrote:
In an earlier contribution to this discussion,
Redwood wrote:

I'm not quite sure what you mean about "power was now flowing around the
circuits" - do you simply mean that there was a finite resistance between
live and neutral, rather than an open circuit?

Guessing, I suspect that the ohmmeter reads fairly close to
short-circuit and the fuse has blown violently, and that a replacement
fuse suffers the same fate. It's worth sacrificing one more fuse to
confirm the hypothesis. (Alternatively use a service technicians' trick
and connect the set to the mains via a 500 W halogen lamp to act as a
current limiter / fuse saver.)

As a pure guess, something - maybe a diode or capacitor - in the internal
power supply has blown, causing the fuse to blow. Locating and replacing the
faulty component may well fix the problem. If you can do it yourself, it may
only cost a few pounds - but it may not be economical if you have to pay
someone else to do it.

IME the most likely component to have failed will be the 'chopper'
transistor in the SMPS - usually a power MOSFET these days, and probably
a 3-legged TO-220 device which can easily be unsoldered and tested with
the multimeter for a source-drain short. If this is the case then
carefully check the snubber network for o/c components or joints, else
you may instantly lose the replacement transistor.

Other possibilities are a s/c RFI filter capacitor in the mains input
circuit, or one or more of the diodes in the mains bridge rectifier.

Yet another possibility is the PTC device ('posistor') in the degaussing
circuit. This is easily disconnected and of course there's no harm in
powering-up a set with the degaussing disconnected, as a test.

Of course a service manual, or at least a circuit diagram is a great
help in finding your way round.

--
Andy

"Andy Wade" wrote in message
...
Roger Mills wrote:
In an earlier contribution to this discussion,
Redwood wrote:

I'm not quite sure what you mean about "power was now flowing around the
circuits" - do you simply mean that there was a finite resistance between
live and neutral, rather than an open circuit?

Guessing, I suspect that the ohmmeter reads fairly close to short-circuit
and the fuse has blown violently, and that a replacement fuse suffers the
same fate. It's worth sacrificing one more fuse to confirm the
hypothesis. (Alternatively use a service technicians' trick and connect
the set to the mains via a 500 W halogen lamp to act as a current limiter
/ fuse saver.)

As a pure guess, something - maybe a diode or capacitor - in the internal
power supply has blown, causing the fuse to blow. Locating and replacing
the faulty component may well fix the problem. If you can do it yourself,
it may only cost a few pounds - but it may not be economical if you have
to pay someone else to do it.

IME the most likely component to have failed will be the 'chopper'
transistor in the SMPS - usually a power MOSFET these days, and probably a
3-legged TO-220 device which can easily be unsoldered and tested with the
multimeter for a source-drain short. If this is the case then carefully
check the snubber network for o/c components or joints, else you may
instantly lose the replacement transistor.

Other possibilities are a s/c RFI filter capacitor in the mains input
circuit, or one or more of the diodes in the mains bridge rectifier.

Yet another possibility is the PTC device ('posistor') in the degaussing
circuit. This is easily disconnected and of course there's no harm in
powering-up a set with the degaussing disconnected, as a test.

Of course a service manual, or at least a circuit diagram is a great help
in finding your way round.

Thanks for all the replies and links. I had another quick look today and
using a DVM I tested for voltage across the new fuse that I replaced inside
the tv. I noticed that when the fuse is in place there is no voltage showing
at either end of the fuse holder terminals - however if I remove the fuse
then there is mains voltage going to one end of the fuse holder but when I
refit the fuse there is no voltage again. Although there is no power
flowing across the fuse, using one of those cheapo continuity testers that
glow when detecting mains voltage, if I hold it within a foot of the tv when
switched on it glows fairly bright when pointed all around the tv - and if
left unplugged for a while and then switch on I do hear a slight noise like
it's recharging the tube or something? Not sure if this narrows things down
any but I think I've gone as far as my capabilities allow on this.

"Redwood" wrote in message
...
"Andy Wade" wrote in message
...
Roger Mills wrote:
In an earlier contribution to this discussion,
Redwood wrote:

I'm not quite sure what you mean about "power was now flowing around the
circuits" - do you simply mean that there was a finite resistance
between
live and neutral, rather than an open circuit?

Guessing, I suspect that the ohmmeter reads fairly close to short-circuit
and the fuse has blown violently, and that a replacement fuse suffers the
same fate. It's worth sacrificing one more fuse to confirm the
hypothesis. (Alternatively use a service technicians' trick and connect
the set to the mains via a 500 W halogen lamp to act as a current limiter
/ fuse saver.)

As a pure guess, something - maybe a diode or capacitor - in the
internal
power supply has blown, causing the fuse to blow. Locating and replacing
the faulty component may well fix the problem. If you can do it
yourself,
it may only cost a few pounds - but it may not be economical if you have
to pay someone else to do it.

IME the most likely component to have failed will be the 'chopper'
transistor in the SMPS - usually a power MOSFET these days, and probably
a
3-legged TO-220 device which can easily be unsoldered and tested with the
multimeter for a source-drain short. If this is the case then carefully
check the snubber network for o/c components or joints, else you may
instantly lose the replacement transistor.

Other possibilities are a s/c RFI filter capacitor in the mains input
circuit, or one or more of the diodes in the mains bridge rectifier.

Yet another possibility is the PTC device ('posistor') in the degaussing
circuit. This is easily disconnected and of course there's no harm in
powering-up a set with the degaussing disconnected, as a test.

Of course a service manual, or at least a circuit diagram is a great help
in finding your way round.

Thanks for all the replies and links. I had another quick look today and
using a DVM I tested for voltage across the new fuse that I replaced
inside
the tv. I noticed that when the fuse is in place there is no voltage
showing
at either end of the fuse holder terminals - however if I remove the fuse
then there is mains voltage going to one end of the fuse holder but when I
refit the fuse there is no voltage again. Although there is no power
flowing across the fuse, using one of those cheapo continuity testers that
glow when detecting mains voltage, if I hold it within a foot of the tv
when
switched on it glows fairly bright when pointed all around the tv - and if
left unplugged for a while and then switch on I do hear a slight noise
like
it's recharging the tube or something? Not sure if this narrows things
down
any but I think I've gone as far as my capabilities allow on this.


I think the last sentence is correct.
Sorry to be a bit of a damp squib, but...

This is a joke, right?
If not, then replace the cover on the TV now.

"Voltage across the fuse"?
Of course there is none if the fuse is good, the fuse is a bit of wire!
Of course there is mains voltage with the fuse removed!
That's correct and normal.

"No power flowing across the fuse"?
I'm sorry, your understanding of how his works is clearly far below the
danger level here.
Put the cover back on.

The cheapo continuity tester glowing in close proximity indicates the main
PSU is up, the Line Timebase is running, and the EHT multiplier is running.
You have around 25,000 volts on the tube anode, ( also the cause of the
power-up crackling noise ) and you have no clue what you are doing. You are
in severe danger of having a very bad experience. Under no circumstances
come anywhere near the fat wire which comes from a 'sucker' on the top rear
of the picture tube, and is held in plastic wraps well away from everything
else. It contains the 25,000v I mentioned.

Put the cover back on.
Now.
Please.

--
Ron

"Ron Lowe" ronATlowe-famlyDOTmeDOTukSPURIOUS wrote in message
...
"Redwood" wrote in message
...
"Andy Wade" wrote in message
...
Roger Mills wrote:
In an earlier contribution to this discussion,
Redwood wrote:

I'm not quite sure what you mean about "power was now flowing around
the
circuits" - do you simply mean that there was a finite resistance
between
live and neutral, rather than an open circuit?

Guessing, I suspect that the ohmmeter reads fairly close to
short-circuit
and the fuse has blown violently, and that a replacement fuse suffers
the
same fate. It's worth sacrificing one more fuse to confirm the
hypothesis. (Alternatively use a service technicians' trick and connect
the set to the mains via a 500 W halogen lamp to act as a current
limiter
/ fuse saver.)

As a pure guess, something - maybe a diode or capacitor - in the
internal
power supply has blown, causing the fuse to blow. Locating and
replacing
the faulty component may well fix the problem. If you can do it
yourself,
it may only cost a few pounds - but it may not be economical if you
have
to pay someone else to do it.

IME the most likely component to have failed will be the 'chopper'
transistor in the SMPS - usually a power MOSFET these days, and probably
a
3-legged TO-220 device which can easily be unsoldered and tested with
the
multimeter for a source-drain short. If this is the case then carefully
check the snubber network for o/c components or joints, else you may
instantly lose the replacement transistor.

Other possibilities are a s/c RFI filter capacitor in the mains input
circuit, or one or more of the diodes in the mains bridge rectifier.

Yet another possibility is the PTC device ('posistor') in the degaussing
circuit. This is easily disconnected and of course there's no harm in
powering-up a set with the degaussing disconnected, as a test.

Of course a service manual, or at least a circuit diagram is a great
help
in finding your way round.

Thanks for all the replies and links. I had another quick look today and
using a DVM I tested for voltage across the new fuse that I replaced
inside
the tv. I noticed that when the fuse is in place there is no voltage
showing
at either end of the fuse holder terminals - however if I remove the fuse
then there is mains voltage going to one end of the fuse holder but when
I
refit the fuse there is no voltage again. Although there is no power
flowing across the fuse, using one of those cheapo continuity testers
that
glow when detecting mains voltage, if I hold it within a foot of the tv
when
switched on it glows fairly bright when pointed all around the tv - and
if
left unplugged for a while and then switch on I do hear a slight noise
like
it's recharging the tube or something? Not sure if this narrows things
down
any but I think I've gone as far as my capabilities allow on this.


I think the last sentence is correct.
Sorry to be a bit of a damp squib, but...

This is a joke, right?
If not, then replace the cover on the TV now.

"Voltage across the fuse"?
Of course there is none if the fuse is good, the fuse is a bit of wire!
Of course there is mains voltage with the fuse removed!
That's correct and normal.

"No power flowing across the fuse"?
I'm sorry, your understanding of how his works is clearly far below the
danger level here.
Put the cover back on.

The cheapo continuity tester glowing in close proximity indicates the main
PSU is up, the Line Timebase is running, and the EHT multiplier is
running. You have around 25,000 volts on the tube anode, ( also the cause
of the power-up crackling noise ) and you have no clue what you are doing.
You are in severe danger of having a very bad experience. Under no
circumstances come anywhere near the fat wire which comes from a 'sucker'
on the top rear of the picture tube, and is held in plastic wraps well
away from everything else. It contains the 25,000v I mentioned.

Put the cover back on.
Now.
Please.

--
Ron

Excuse me Ron but I do know that a tv carries around 30k volts and I have no
intension of going anywhere near "the big fat wire" or capasitors. I do
realise that a tv is the 2nd most potentially dangerous equipment in the
hosehold behind the microwave.

Redwood wrote:

Excuse me Ron but I do know that a tv carries around 30k volts and I have no
intension of going anywhere near "the big fat wire" or capasitors. I do
realise that a tv is the 2nd most potentially dangerous equipment in the
hosehold behind the microwave.


That's good, because I share some of Ron's doubts.

The lack of voltage across the fuse indicates it is doing its normal job
- transferring electricity from one end to the other - rather than its
alternative job - preventing far too much power from flowing.

An old TV isn't worth the risk.

Andy

On Mon, 7 Apr 2008 10:06:07 +0100, "Redwood" wrote:

There's probably a million and one things that could be wrong but I just
wondered if anyone could hazard a guess why my portable TV is dead.

The only success I've had repairing my TVs is to check for dry joints
and check for leaking/bulging capacitors in the mains power supply
circuit.
If any of the cylinder shaped components with +/- on them look like
they've expanded then it may be worth trying to replace them.
(I usually get my hig voltage caps from farnell and make the order up
to £30 or so for free delivery)

As others have pointed out BE CAREFUL. Make sure any working caps have
been discharged first.

wrote in message
...
On Mon, 7 Apr 2008 10:06:07 +0100, "Redwood" wrote:

There's probably a million and one things that could be wrong but I just
wondered if anyone could hazard a guess why my portable TV is dead.

The only success I've had repairing my TVs is to check for dry joints
and check for leaking/bulging capacitors in the mains power supply
circuit.
If any of the cylinder shaped components with +/- on them look like
they've expanded then it may be worth trying to replace them.
(I usually get my hig voltage caps from farnell and make the order up
to £30 or so for free delivery)

As others have pointed out BE CAREFUL. Make sure any working caps have
been discharged first.


I've had mains switches fail.

In article ,
"John" writes:

wrote in message
...
On Mon, 7 Apr 2008 10:06:07 +0100, "Redwood" wrote:

There's probably a million and one things that could be wrong but I just
wondered if anyone could hazard a guess why my portable TV is dead.

The only success I've had repairing my TVs is to check for dry joints
and check for leaking/bulging capacitors in the mains power supply
circuit.
If any of the cylinder shaped components with +/- on them look like
they've expanded then it may be worth trying to replace them.
(I usually get my hig voltage caps from farnell and make the order up
to £30 or so for free delivery)

As others have pointed out BE CAREFUL. Make sure any working caps have
been discharged first.

I've had mains switches fail.

Low power resistors subject to either high voltage or
high current changing their values is not uncommon too.

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