TV Picture Symptom

[[email protected]]

Hi,

I have a chance to pick up a nice 32" TV for free. Not sure of the
brand or model yet, but the owner says it only displays 3/4 of the
picture until the set warms up for 5 minutes, then it's fine until
shut down.

What would typically cause this and is it a fairly easy repair? I
have soldering skills, etc. but am not a tech.

Thanks.

 

[Jerry G.]

It sounds like there are some components that have become thermo
sensitive from age. Most of the time, this is caused by capacitors
going high in ESR.

To service your set, you will need to have TV service training, a good
knowledge of electronics, and the tools to troubleshoot and service
the set. There are serious safety issues when working on TV sets.

I would suggest taking the TV in for an estimate for repairs. I am
sure that the previous owner is replacing the TV for obvious reasons
rather than having it serviced.


Jerry G.
======

 

[b]

Hi,

I have a chance to pick up a nice 32" TV for free. Not sure of the
brand or model yet, but the owner says it only displays 3/4 of the
picture until the set warms up for 5 minutes, then it's fine until
shut down.

What would typically cause this and is it a fairly easy repair? I
have soldering skills, etc. but am not a tech.

Thanks.

if the picture is squashed vertically i.e a gap at the top or bottom
of the screeen chances are its capacitors in the vertical/frame output
stage. That is fixable.however this is pure guesswork, we don't have
much to go on!

when you pick it up, we will need a picture of the screen to get a
better idea..
-B

 

[Reactor]

Hi,

I have a chance to pick up a nice 32" TV for free. Not sure of the
brand or model yet, but the owner says it only displays 3/4 of the
picture until the set warms up for 5 minutes, then it's fine until
shut down.

What would typically cause this and is it a fairly easy repair? I
have soldering skills, etc. but am not a tech.

Thanks.

Thanks guys. I will see if I can still score it and get back to you.

Jerry - I am well advised on the dangers of working on TVs. It's been 20+
years, but I took electronics in vocational technical school, and have been
reading a lot about the repair of classic arcade games.

Regardless, I sincerely appreciate the advice that you gave, and the concern
that drove you to give it.

Stay tuned.

 

[James Sweet]

Hi,

I have a chance to pick up a nice 32" TV for free. Not sure of the
brand or model yet, but the owner says it only displays 3/4 of the
picture until the set warms up for 5 minutes, then it's fine until
shut down.

What would typically cause this and is it a fairly easy repair? I
have soldering skills, etc. but am not a tech.

Thanks.

Bad capacitors in the vertical section, you don't really need any special
tools, just replace all the suspects, it'll only cost a few dollars. This is
a good candidate for a beginner learning to repair TVs.

 

[Sam Goldwasser]

Bad capacitors in the vertical section, you don't really need any special
tools, just replace all the suspects, it'll only cost a few dollars. This is
a good candidate for a beginner learning to repair TVs.

Agreed. But make sure you understand and follow the SAFETY guidelines.

Service information will also help to identify the suspect parts.
Your local large public library may get the Sams' Photofacts.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[Tov]

Bad capacitors in the vertical section, you don't really need any special
tools, just replace all the suspects, it'll only cost a few dollars. This is
a good candidate for a beginner learning to repair TVs.

Would the same apply if there were *no* picture (apart from menu
items) for the first five minutes while the set warms up? This is
the problem I'm having with one of mine.

 

[Meat Plow]

Bad capacitors in the vertical section, you don't really need any special
tools, just replace all the suspects, it'll only cost a few dollars. This is
a good candidate for a beginner learning to repair TVs.

Beginner in what, TV repair? From what I read between the lines this guy
is your average Joe that knows how to solder to some degree looking for a
cheapo TV and not looking to start repairing them. He's going to need to
know all the safety precautions, how to identify parts, where the vertical
components are located, etc...etc... This is a lot of hand holding and not
really a viable repair via Usenet considering all of the above. Don't get
me wrong I'm all for the newbie willing to learn these things but I don't
think it applies to someone who has no idea whatsoever what he's doing.

 

[none]

Agreed. But make sure you understand and follow the SAFETY guidelines.

Service information will also help to identify the suspect parts.
Your local large public library may get the Sams' Photofacts.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

If you are very careful, you can narrow your search area by using a heat
gun on the capacitors and it will be obvious which capacitor is at
fault.
Since this requires operating the TV with the back off, do not do this
unless you are very careful and have set up an access scheme where you
can get to the capacitors and see the screen and not have to touch
anything while the power is on. Also be careful of the high voltage
on the crt which will be there even on power off.
If you are not careful with the heat gun, you will have more parts to
replace than when you started. A hair dryer may also work and have
fewer opportunities for mischief.
I did this on a TV a few years ago and the culprit was a small 10uf
cap. It has worked fine for ever since.

 

[Tov]

If you are very careful, you can narrow your search area by using a heat
gun on the capacitors and it will be obvious which capacitor is at
fault.

How exactly will it be obvious?

 

[none]

How exactly will it be obvious?

If the picture is restored to normal when the set heats up, heating
the failing capacitor will restore the picture height. Conversely,
cooling it will make the picture shrink. In my TV, it was pretty
dramatic. In my case, the capacitor, while part of the vertical
circuit, was in another place on the board so doing a general
replacement of the vertical capacitors would probably had me missing
this one.
Also, searching on the web for this got useful hits about others
having the same problem. This way took less than an hour including
dealing with the case.
The bad capacitor had a big effect on the picture but none of the others
did much of anything. First isolate the problem to a large area and
then block off enough of the hot air output to localize the individual
capacitor.

 

[James Sweet]

Would the same apply if there were *no* picture (apart from menu
items) for the first five minutes while the set warms up? This is
the problem I'm having with one of mine.

Maybe, but if it's a Sony set, it's probably the AKB circuit blanking the
pucture because the CRT is weak.

 

[James Sweet]

Beginner in what, TV repair? From what I read between the lines this guy
is your average Joe that knows how to solder to some degree looking for a
cheapo TV and not looking to start repairing them. He's going to need to
know all the safety precautions, how to identify parts, where the vertical
components are located, etc...etc... This is a lot of hand holding and not
really a viable repair via Usenet considering all of the above. Don't get
me wrong I'm all for the newbie willing to learn these things but I don't
think it applies to someone who has no idea whatsoever what he's doing.

A lot of people on this group are quick to assume that everyone
inexperienced is an idiot and has no hope. Yes there's some safety issues,
though as a practical matter this applies more to the implosion hazard of
the CRT than high voltages, don't touch anything in the set with your hand
while it's plugged in, unplugged a modern TV will discharge itself within
moments in most cases. I've stepped a lot of novices through repairing
arcade game monitors, and a TV is really no different.

Read Sam's FAQ and get out a hair dryer and some freeze spray (a can of air
duster held upside down works just as well) and go for it.

 

[Meat Plow]

A lot of people on this group are quick to assume that everyone
inexperienced is an idiot and has no hope. Yes there's some safety issues,
though as a practical matter this applies more to the implosion hazard of
the CRT than high voltages, don't touch anything in the set with your hand
while it's plugged in, unplugged a modern TV will discharge itself within
moments in most cases. I've stepped a lot of novices through repairing
arcade game monitors, and a TV is really no different.

Read Sam's FAQ and get out a hair dryer and some freeze spray (a can of air
duster held upside down works just as well) and go for it.

Please note that nowhere in my reply did I say or imply the OP was a
hopeless idiot.

 

[Tov]

If the picture is restored to normal when the set heats up, heating
the failing capacitor will restore the picture height. Conversely,
cooling it will make the picture shrink.

Interesting. But presumably this method only works for warm-up
problems and cannot be adapted to failing capacitors in general?

 

[none]

Interesting. But presumably this method only works for warm-up
problems and cannot be adapted to failing capacitors in general?

It is a bit more general than that but is not universal. If a part has
completely failed, heating or cooling do not change how it works. But
failing parts often change characteristics when heated. Heat guns and
freeze mist have long been used for this kind of troubleshooting. It
just means you should start troubleshooting when things first start
going bad rather than waiting until you have a complete failure.

 

[Meat Plow]

Interesting. But presumably this method only works for warm-up
problems and cannot be adapted to failing capacitors in general?

It is generally understood that in some cases warming a capacitor will
restore its function enough to remove whatever fault it created in a
circuit. This is the theory that some of us have based our diagnosis of
your set upon. If correct you could purposely heat that capacitor up while
the vertical problem was manifested and within seconds, not minutes the
vertical would resume to normal size. Same goes that you could cool the
capacitor and watch the vertical shrink.

Semiconductors behave similarly but in opposite. Cooling a noisy or
leaky semiconductor (not shorted or burned open) in some instances
can make them operate normally until they warm. I've been using these
trouble shooting techniques for many years.