Toshiba TV29C90 problem; Image fades to black...

[Jim Yanik]

Wiebe Cazemier <wiebe@halfgaar.net> wrote in
news:7a2a3$4819d907$d4cc82be$20123@cache2.tilbu1.nb.home.nl:

Hi,

I've been having troubles with an Eizo T766 19" CRT; the blue and red
gun occasionally turn fully on, most notably when tapping the neck
board, with visible verticle retrace for that color. At first I
thought I narrowed the problem down as being inside the CRT, because I
desoldered the offending guns' pins from the neck board, and the
problem remained. However, it has come to my attention that the
problem could also very well be in the CRT socket, the spark gaps to
be precise. The "Notes on the Troubleshooting and Repair of Television
Sets" article on www.repairfaq.org says this about it:

Except for the high voltage to other places, the short may actually
be
located in the CRT *socket* or even on the CRT neck board, probably in
the spark gap(s) for the problem pins. Remove the socket and test
between the suspect pins on the CRT itself. If the CRT itself is fine,
the spark gaps should be inspected and cleaned/repaired and/or
components replaced.

I don't know a lot about CRT's, and their sockets, so I've got a
question. What are the spark gaps? Are those the holes next to the pin
connectors? The socket for my tube is shown in [1]. And how do I
repair them (if they are what I think they are, they are difficult to
reach).

The short does not measure with the continuity tester on my DMM, and
not even with the 200 MOhm resistance tester (neither with the socket
connected to the CRT, or hanging loose, so it's difficult to test if
the socket is actually the cause. But if it were, would I measure a
short between the pin connector and ground?

[1] http://www.halfgaar.net/posts/2008-05/eizo-crt-socket

I believe the spark gaps look like disc capacitors with a slit in the
top edge.
I had a TV with bad solder joints on the CRT socket PCB,caused similar
problems.

the CRT socket could be loose for some pins.(the individual pin sockets
being spread open too much,not gripping the CRT pin tightly)

--
Jim Yanik
jyanik
at
kua.net

 

[Jim Yanik]

Wiebe Cazemier <wiebe@halfgaar.net> wrote in
news:7a2a3$4819d907$d4cc82be$20123@cache2.tilbu1.nb.home.nl:

Hi,

I've been having troubles with an Eizo T766 19" CRT; the blue and red
gun occasionally turn fully on, most notably when tapping the neck
board, with visible verticle retrace for that color. At first I
thought I narrowed the problem down as being inside the CRT, because I
desoldered the offending guns' pins from the neck board, and the
problem remained. However, it has come to my attention that the
problem could also very well be in the CRT socket, the spark gaps to
be precise. The "Notes on the Troubleshooting and Repair of Television
Sets" article on www.repairfaq.org says this about it:

Except for the high voltage to other places, the short may actually
be
located in the CRT *socket* or even on the CRT neck board, probably in
the spark gap(s) for the problem pins. Remove the socket and test
between the suspect pins on the CRT itself. If the CRT itself is fine,
the spark gaps should be inspected and cleaned/repaired and/or
components replaced.

I don't know a lot about CRT's, and their sockets, so I've got a
question. What are the spark gaps? Are those the holes next to the pin
connectors? The socket for my tube is shown in [1]. And how do I
repair them (if they are what I think they are, they are difficult to
reach).

The short does not measure with the continuity tester on my DMM, and
not even with the 200 MOhm resistance tester (neither with the socket
connected to the CRT, or hanging loose, so it's difficult to test if
the socket is actually the cause. But if it were, would I measure a
short between the pin connector and ground?

[1] http://www.halfgaar.net/posts/2008-05/eizo-crt-socket

I believe the spark gaps look like disc capacitors with a slit in the
top edge.
I had a TV with bad solder joints on the CRT socket PCB,caused similar
problems.

the CRT socket could be loose for some pins.(the individual pin sockets
being spread open too much,not gripping the CRT pin tightly)

--
Jim Yanik
jyanik
at
kua.net

 

[bz]

Wiebe Cazemier <wiebe@halfgaar.net> wrote in
news:7a2a3$4819d907$d4cc82be$20123@cache2.tilbu1.nb.home.nl:

Hi,

I've been having troubles with an Eizo T766 19" CRT; the blue and red
gun occasionally turn fully on, most notably when tapping the neck
board, with visible verticle retrace for that color. At first I thought
I narrowed the problem down as being inside the CRT, because I
desoldered the offending guns' pins from the neck board, and the problem
remained. However, it has come to my attention that the problem could
also very well be in the CRT socket, the spark gaps to be precise. The
"Notes on the Troubleshooting and Repair of Television Sets" article on
www.repairfaq.org says this about it:

Except for the high voltage to other places, the short may actually be
located in the CRT *socket* or even on the CRT neck board, probably in
the spark gap(s) for the problem pins. Remove the socket and test
between the suspect pins on the CRT itself. If the CRT itself is fine,
the spark gaps should be inspected and cleaned/repaired and/or
components replaced.

I don't know a lot about CRT's, and their sockets, so I've got a
question. What are the spark gaps? Are those the holes next to the pin
connectors? The socket for my tube is shown in [1]. And how do I repair
them (if they are what I think they are, they are difficult to reach).

Need to see the OTHER side of the board. Those sparkgaps I am familiar with
look like a small ceramic disk capacitor with a slit cut into the edge
perpendicular to the disk.

They might be INSIDE the body of the socket (white plastic thing on the
board you are holding).

The short does not measure with the continuity tester on my DMM, and not
even with the 200 MOhm resistance tester (neither with the socket
connected to the CRT, or hanging loose, so it's difficult to test if the
socket is actually the cause. But if it were, would I measure a short
between the pin connector and ground?

[1] http://www.halfgaar.net/posts/2008-05/eizo-crt-socket

--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap

 

[bz]

Wiebe Cazemier <wiebe@halfgaar.net> wrote in
news:7a2a3$4819d907$d4cc82be$20123@cache2.tilbu1.nb.home.nl:

Hi,

I've been having troubles with an Eizo T766 19" CRT; the blue and red
gun occasionally turn fully on, most notably when tapping the neck
board, with visible verticle retrace for that color. At first I thought
I narrowed the problem down as being inside the CRT, because I
desoldered the offending guns' pins from the neck board, and the problem
remained. However, it has come to my attention that the problem could
also very well be in the CRT socket, the spark gaps to be precise. The
"Notes on the Troubleshooting and Repair of Television Sets" article on
www.repairfaq.org says this about it:

Except for the high voltage to other places, the short may actually be
located in the CRT *socket* or even on the CRT neck board, probably in
the spark gap(s) for the problem pins. Remove the socket and test
between the suspect pins on the CRT itself. If the CRT itself is fine,
the spark gaps should be inspected and cleaned/repaired and/or
components replaced.

I don't know a lot about CRT's, and their sockets, so I've got a
question. What are the spark gaps? Are those the holes next to the pin
connectors? The socket for my tube is shown in [1]. And how do I repair
them (if they are what I think they are, they are difficult to reach).

Need to see the OTHER side of the board. Those sparkgaps I am familiar with
look like a small ceramic disk capacitor with a slit cut into the edge
perpendicular to the disk.

They might be INSIDE the body of the socket (white plastic thing on the
board you are holding).

The short does not measure with the continuity tester on my DMM, and not
even with the 200 MOhm resistance tester (neither with the socket
connected to the CRT, or hanging loose, so it's difficult to test if the
socket is actually the cause. But if it were, would I measure a short
between the pin connector and ground?

[1] http://www.halfgaar.net/posts/2008-05/eizo-crt-socket

--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap

 

[Gareth Magennis]

"Sam Goldwasser" <sam@plus.seas.upenn.edu> wrote in message
news:6w3ap19b1v.fsf@plus.seas.upenn.edu...

This receiver seems to work fine in every respect except that the volume
knob has to be turned up to a modest value before the speakers come on.
This
will occur regardless of whether the speakers are actually enabled.

After that, it will usually run at any volume until power cycled

It has been sitting unused for about 10 years but don't know if this
was a problem back then.

Any common issues with this model?

Thanks.

Often this is down to dirty speaker relay contacts. If it has output
relays. Sometimes you can pop the top off them to spray the contacts,
others are sealed and need to be replaced.

Signal relays do much the same thing by the way.

If you see any relays inside, try getting it in the state where the speakers
aren't working and then start tapping them with a stick.



Gareth.

 

[Gareth Magennis]

"Sam Goldwasser" <sam@plus.seas.upenn.edu> wrote in message
news:6w3ap19b1v.fsf@plus.seas.upenn.edu...

This receiver seems to work fine in every respect except that the volume
knob has to be turned up to a modest value before the speakers come on.
This
will occur regardless of whether the speakers are actually enabled.

After that, it will usually run at any volume until power cycled

It has been sitting unused for about 10 years but don't know if this
was a problem back then.

Any common issues with this model?

Thanks.

Often this is down to dirty speaker relay contacts. If it has output
relays. Sometimes you can pop the top off them to spray the contacts,
others are sealed and need to be replaced.

Signal relays do much the same thing by the way.

If you see any relays inside, try getting it in the state where the speakers
aren't working and then start tapping them with a stick.



Gareth.

 

[James Sweet]

"David" <someone@some-where.com> wrote in message
news:W_nSj.12392$V14.3123@nlpi070.nbdc.sbc.com...

http://www.halfgaar.net/posts/2008-05/crt-socket-back

There are no parts except a few SMD capacitors, as far as I can see. And
there
is nothing whatsoever in the white body (I desoldered it to have a look.

As posted, the spark gaps may be physically inside the crt socket
assembly itself. The odds of disassembly and proper reassembly of most of
these sockets is actually relatively low. It may be done with proper
tools and techniques.
What you may find is that due to arcing at the gaps or external
contaminates that the surfaces may have become carbonized and pitted. At
that point it may be best to look for a new crt socket and just replace
it.

What are the components SGH30,31,32? These are between the cathodes and
ground. These may be you spark gaps.

David

They almost certainly are. I've seen the SG designation used for spark gaps
before. Some look like capacitors, some look like neon glow lamps, others
look like diodes or resistors, all function pretty much the same.

 

[James Sweet]

"David" <someone@some-where.com> wrote in message
news:W_nSj.12392$V14.3123@nlpi070.nbdc.sbc.com...

http://www.halfgaar.net/posts/2008-05/crt-socket-back

There are no parts except a few SMD capacitors, as far as I can see. And
there
is nothing whatsoever in the white body (I desoldered it to have a look.

As posted, the spark gaps may be physically inside the crt socket
assembly itself. The odds of disassembly and proper reassembly of most of
these sockets is actually relatively low. It may be done with proper
tools and techniques.
What you may find is that due to arcing at the gaps or external
contaminates that the surfaces may have become carbonized and pitted. At
that point it may be best to look for a new crt socket and just replace
it.

What are the components SGH30,31,32? These are between the cathodes and
ground. These may be you spark gaps.

David

They almost certainly are. I've seen the SG designation used for spark gaps
before. Some look like capacitors, some look like neon glow lamps, others
look like diodes or resistors, all function pretty much the same.

 

[Arfa Daily]

"Wiebe Cazemier" <wiebe@halfgaar.net> wrote in message
news:b603a$481a4dc2$d4cc82be$19077@cache4.tilbu1.nb.home.nl...

Hi,

Over the past few days I've been analysing a problem in my Eizo T766 19"
CRT
(Sony Trinitron tube), with this group's help. Unfortunately, I can
conclude
nothing else besides that the red and blue gun occasionally short to
something
at low potential, most likely the heater. I tried tapping it loose, but
with
no success. So, now I'd like to collect as much information as possible
about
zapping the short out.

I've seen suggested that you can use a neon transformer (or other kind of
tesla
coil) for this: connect both pins of the heater to eachother, and connect
the
transformer between it and the affected cathode (one at a time). This
seems
rather dangerous to me; such arcing usually leaves everything blackened.
If
this is a good approach, what voltage neon transformer should I look for?

Another method is a capacitor charged up to several hundred volts; start
with a
few uF, then increase as desired.

I would like to know, based on people's experience, how much chance I have
of
blowing out the cathode or filament. Bear in mind that it's an
intermittant
short, that does not show up on the DMM when the tube is unpowered (not
even
on the 200 MOhm range), so in the most positive situation, we're talking
about
loose debris which needs to get out of the way, and not a dead short.

One last question: is the heater filament an exposed (or covered?) fragile
filament like that in light bulb, or is more robust like heating wire of
an
electric stove?

Any help is appreciated, and thanks in advance.

Wiebe Cazemier

My B&K CRT analyser / restorer removed shorts by discharging a cap across
the affected electrodes. I seem to recall that g1-k shorts were actually
more common, due to 'burnt out' emissive material falling off the cathode
and lodging in the g1-k gap. The location of the short was indicated by neon
lamps, the intensity of the glow giving an indication of the resistance of
the path. When the zapping took place, I think that the CRT gun was being
run by the analyser as a basic triode. Some quite spectacular fireworks used
to occur in the neck, as the contaminating material was vapourised by the
discharge across it from the cap. It was very effective at removing
inter-electrode leakage paths. The B&K was a fine instrument in its day. I
lent mine to someone some years back, and it was never returned. I can't
even remember who it was to ...

CRT heaters are not particularly fragile, and are insulated from the cathode
cylinder, by a heat conducting coating. If you are discharging between h and
k, then the heater pins should be shorted together to avoid one of those
'unfortunate accidents' ... And of course, make sure that the base connector
is removed from the tube !!

Arfa

 

[Arfa Daily]

"Wiebe Cazemier" <wiebe@halfgaar.net> wrote in message
news:10fb1$481a13e2$d4cc82be$29149@cache1.tilbu1.nb.home.nl...

On Thursday 01 May 2008 20:17, Art wrote:

As posted, the spark gaps may be physically inside the crt socket
assembly
itself. The odds of disassembly and proper reassembly of most of these
sockets is actually relatively low. It may be done with proper tools and
techniques.
What you may find is that due to arcing at the gaps or external
contaminates
that the surfaces may have become carbonized and pitted. At that point it
may be best to look for a new crt socket and just replace it.

This is the socket itself, the underside:

http://www.halfgaar.net/posts/2008-05/crt-socket-underside

I don't see anything that could be a spark gap. It just seems to be a
piece of
plastic to connect the tube to the neck board.

A quote from David's post:

What are the components SGH30,31,32? These are between the
cathodes and ground. These may be you spark gaps.

Those are those resistor-like devices I mentioned, which' symbol is two
arrows
pointing to eachother. I indeed suspected them as the spark gaps.
Unfortunately, this means that the short is really in the CRT, because the
problem persisted with the red and blue pins desoldered from the PCB.
Unless
my tapping caused them to connect briefly, but I doubt that.

A sharp rap or two to the neck of the CRT, using the butt end of a
screwdriver, and with the monitor / TV on its side or upside down (but NOT
on its face) can often be effective at dislodging material that has fallen
off the cathode surface into the g1-k gap. The 'resistor' looking devices
called "SG" are the spark gaps. The opposing arrows symbol is standard for
this type of device. Any slots - often with curved opposing faces - milled
in the PCB material, with copper up to the edge of the gap, are also spark
gaps. These can get dusty contamination across them. It is also not at all
uncommon to have a grounded wire ring running around the outside of all the
pins, inside the plastic base connector. However, from your description, it
certainly sounds as though the problem is internal to the CRT.

Arfa

 

[Arfa Daily]

<snip>

AC power adaptors are misnamed because they are mostly DC power adaptors,
i.e. they output DC. This means that the centre pin can be either
negative or positive, there is no fixed convention. Which means that if
you plug a positive pin power supply into a pedal which is meant to have a
negative pin power supply, you run the risk of burning out a diode and
possibly one of the 3 IC's and having to post on usenet for help in trying
to fix it.
Do not just go around plugging every wall wart you have into every piece
of equipment you have as you will very soon have several dead pieces of
equipment, dead wall warts, or both. Which is quite possibly what you have
right now. Especially if the wall wart output is a higher voltage than
the equipment requires.

Some wall warts really are AC adaptors in that they output AC. Plug this
into all of your pieces of equipment you have lying around and you have
double the chance of burning out your equipment or wall wart, as they
output both positive and negative voltages at the same time.



Blimey.

I'd say this was a good possibility. For the last 8 or 10 years, the nearest
thing to a 'convention' that equipment with coaxial DC connectors has had,
is that the centre pin is "+", so that's the way that the wall warts are
configured. However, that pedal that you are repairing, defies this
'convention' in having a negative centre pin, and this is actually quite
common on pedals. So, if you plug in a common 'modern' wall wart, that's
*likely* - although not guaranteed - to have a positive centre connection,
then the result will be at best that the pedal just doesn't work (D1 being
in circuit for an external power supply input will 'block' and allow no
current to pass), and at worst, will damage a shunt protection diode if one
is fitted without a series diode, as you seem to be suggesting is actually
the case, contrary to what the schematic says. Worse, if there is no
protection of any type, then the result will be destroyed IC's in the
twinkle of an eye ...

Note all of what Gareth has said. It's all good stuff. Should you have any
trouble laying hands on 4558 opamps, you can also use bi-fet low noise types
such as TL072 or TL082 in most all dual opamp applications in this type of
equipment.

Arfa

 

[Gareth Magennis]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:fntSj.5659$b4.1096@newsfe1-gui.ntli.net...

snip


AC power adaptors are misnamed because they are mostly DC power adaptors,
i.e. they output DC. This means that the centre pin can be either
negative or positive, there is no fixed convention. Which means that if
you plug a positive pin power supply into a pedal which is meant to have
a negative pin power supply, you run the risk of burning out a diode and
possibly one of the 3 IC's and having to post on usenet for help in
trying to fix it.
Do not just go around plugging every wall wart you have into every piece
of equipment you have as you will very soon have several dead pieces of
equipment, dead wall warts, or both. Which is quite possibly what you
have right now. Especially if the wall wart output is a higher voltage
than the equipment requires.

Some wall warts really are AC adaptors in that they output AC. Plug this
into all of your pieces of equipment you have lying around and you have
double the chance of burning out your equipment or wall wart, as they
output both positive and negative voltages at the same time.



Blimey.


I'd say this was a good possibility. For the last 8 or 10 years, the
nearest thing to a 'convention' that equipment with coaxial DC connectors
has had, is that the centre pin is "+", so that's the way that the wall
warts are configured. However, that pedal that you are repairing, defies
this 'convention' in having a negative centre pin, and this is actually
quite common on pedals. So, if you plug in a common 'modern' wall wart,
that's *likely* - although not guaranteed - to have a positive centre
connection, then the result will be at best that the pedal just doesn't
work (D1 being in circuit for an external power supply input will 'block'
and allow no current to pass), and at worst, will damage a shunt
protection diode if one is fitted without a series diode, as you seem to
be suggesting is actually the case, contrary to what the schematic says.
Worse, if there is no protection of any type, then the result will be
destroyed IC's in the twinkle of an eye ...

Note all of what Gareth has said. It's all good stuff. Should you have any
trouble laying hands on 4558 opamps, you can also use bi-fet low noise
types such as TL072 or TL082 in most all dual opamp applications in this
type of equipment.

Arfa

Yep, and if you want to run it on disposable batteries, you can choose an
Op-amp with a lower current draw.


Gareth.

 

[Gareth Magennis]

"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:481B303E.8A134A3D@hotmail.com...

rubenstein.martin@googlemail.com wrote:

The original CMOS battery in my laptop - a 2032 lithium coin cell -
lasted 5 years. Since then the various replacements seem to last
only 6 to 9 months.

Where are you buying them from ?

Graham

I still smile at my naiveness at buying a whole bunch of "Duracell" AA's for
a pound at one of those pound shops before going travelling in India. When
my Maglite eventually needed a change of batteries, I discovered that every
one was as flat as a fart.



Gareth.


Gareth.

 

[Nigel Heather]

Agreed,

My wife's watch battery failed after 2 years. Thought I'd be clever by
buying a set of 12 batteries on eBay for the same price as a branded one.

The generics lasted a month each.

Gave up after I had replaced 3 and just bought a proper branded battery
(Maxcell in this case) still going strong 1 year later.

Cheers,

Nigel

 

[James Sweet]

Floating the heater in a monitor is not usually possible because they
run the heaters on a regulated DC supply instead of using AC from the
flyback. DC obviously won't work with a CRT heater isolation
transformer. I have seen other Sony monitor CRTs with 5v heaters, so
it may be fine. If your monitor does use AC heaters, then you need a
true RMS meter to measure this voltage.

I did isolate the heater on a Sony monitor once years ago, it was a DC
heater but I disconnected the plug and then wound a couple turns of wire
around the flyback core and used that instead, it worked great for a day,
but the cathodes were shot so I added another turn and it was bright again
for an hour or so, then it got unusably dim again, added another turn and
the heater burned out. The picture did look fine while it worked though.

 

[James Sweet]

Floating the heater in a monitor is not usually possible because they
run the heaters on a regulated DC supply instead of using AC from the
flyback. DC obviously won't work with a CRT heater isolation
transformer. I have seen other Sony monitor CRTs with 5v heaters, so
it may be fine. If your monitor does use AC heaters, then you need a
true RMS meter to measure this voltage.

I did isolate the heater on a Sony monitor once years ago, it was a DC
heater but I disconnected the plug and then wound a couple turns of wire
around the flyback core and used that instead, it worked great for a day,
but the cathodes were shot so I added another turn and it was bright again
for an hour or so, then it got unusably dim again, added another turn and
the heater burned out. The picture did look fine while it worked though.

 

[James Sweet]

"Yukio YANO" <yano@shaw.ca> wrote in message
news:epHSj.107916$rd2.26978@pd7urf3no...

Fred wrote:
4-years old eMachines system. CRT monitor image on one part of the
screen "jumps" a 1/2 inch or so every minute or 2. (Movement appears
in different places and seems to be sideways.) Any suggestions?

LCD Monitors !

Electro-magnetic interference to the CRT !

Try moving the CRT Monitor and point it in a different direction as a
diagnostic.

LCD monitors do not use electro-static or electro-
magnetic deflection or scanning, so are not bothered by strong external
Magnetic fields


Yukio YANO

I hate LCD monitors, they look like crap to me, and yes I have a very nice
one on my desk at work, it's fine for what I do there, but I'm keeping my
flat CRT at home, much nicer.

 

[James Sweet]

"Yukio YANO" <yano@shaw.ca> wrote in message
news:epHSj.107916$rd2.26978@pd7urf3no...

Fred wrote:
4-years old eMachines system. CRT monitor image on one part of the
screen "jumps" a 1/2 inch or so every minute or 2. (Movement appears
in different places and seems to be sideways.) Any suggestions?

LCD Monitors !

Electro-magnetic interference to the CRT !

Try moving the CRT Monitor and point it in a different direction as a
diagnostic.

LCD monitors do not use electro-static or electro-
magnetic deflection or scanning, so are not bothered by strong external
Magnetic fields


Yukio YANO

I hate LCD monitors, they look like crap to me, and yes I have a very nice
one on my desk at work, it's fine for what I do there, but I'm keeping my
flat CRT at home, much nicer.

 

[James Sweet]

AC power adaptors are misnamed because they are mostly DC power adaptors,
i.e. they output DC. This means that the centre pin can be either
negative or positive, there is no fixed convention. Which means that if
you plug a positive pin power supply into a pedal which is meant to have
a negative pin power supply, you run the risk of burning out a diode and
possibly one of the 3 IC's and having to post on usenet for help in
trying to fix it.

They're not misnamed, they're called AC adapters because they adapt the AC
mains to whatever the equipment being powered requires, whether that be AC
or DC.

 

[James Sweet]

AC power adaptors are misnamed because they are mostly DC power adaptors,
i.e. they output DC. This means that the centre pin can be either
negative or positive, there is no fixed convention. Which means that if
you plug a positive pin power supply into a pedal which is meant to have
a negative pin power supply, you run the risk of burning out a diode and
possibly one of the 3 IC's and having to post on usenet for help in
trying to fix it.

They're not misnamed, they're called AC adapters because they adapt the AC
mains to whatever the equipment being powered requires, whether that be AC
or DC.