My TV is going, going....

[Sambuchi]

almost gone.

I have a small tube tv in my bedroom.
When I turn it on the middle line will appear and the rest of the screen will be blank. After a few min , the screen will pop up. I am not a TV guy and know some here are... any inputs?

Trust me.. it wont take much for me to do a small upgrade!

_________________
Tony
You can look at my projects here www.sambuchi.net

[Externet]

Hi Tony,
Try re-soldering vertical deflection, power supply and high voltage nodes on the printed circuit bord.
Miguel

[haklesup]

Works when cold then fails when warm is either a bad semiconductor or a cold solder joint but Fails when cold and works when warm is usually the signature of a cold solder joint.

The vertical deflection circuit is a natural place to start looking since that is what your picture lacks. HV is ok because you have a line as such is the H deflection ckt.

Most likely place to look is the largest transistors mounted simultaneously to a heat sink and PCB and just as likely, the tiny pins of any SMT IC chips, look for corrosion caused by uncleaned flux or foreign substance (like coca cola)

Probing the solder joints, connectors and flexing boards with a wooden or other non conductive tool while the TV is powered is a good method for finding failed interconnects. There is still a chance that it is an actual component failure but the symptoms indicates that is unlikely.

Or maybe your TV saw the new ads about Analog TV signal ending and it committed suicide to avoid the shame of loosing all reception. Poor little guy was suffering from LCD envy. I suspect a firm whack in the chassis will knock some sense back into it. Or if tough love isn't your thing, tell it you'll hook it up to a sweet converter box or give it a new life as a manniquen head.

[Janitor Tzap]

I agree with haklesup.

It has the making of a bad solder joint.

Pop open the case on the set, and find the Vertical Section.
Brake out the lighted magnifier, and look over the connections to the Deflection Yoke.
Then work back into the Vertical Driver Circuit.
If you can't see anything.

Have a mirror setup so you can see the screen of the set.
Turn on the set, let it warm up so you have a picture.
Grab a can of "Freeze It" and start targeting the connections, and drive components.
When you duplicate the symptom by cooling the component.
First try re-soldering it down.
Then re-try it.
Also use the "Freeze It" on the component.
If cooling it down still causes the symptom to happen.
Then replace that component.
Thou, since you didn't give the age of this television.
Don't be surprised that you can't still get some components.


Signed: Janitor Tzap

[Sambuchi]

ok.. wow lots of ideas! I like it!

well the TV is 7 yrs old.

The problem that I explained above is how it started.
The past few days it seems to come and go...
even when the TV turns on fine, after a period of time... may very .i will get one line.

well, I am home today and about to rip this thing apart.

I remember when I was 6-7 yrs
"in an attempt to fix a stacticy reception "
I took apart my moms beloved portable tv..
after pretty much destroying the thing and not being able to put it back together..
i hid the remaining pieces under my bed. I caught some heat for that..

come to think of it... that was the last time I took apart a tv.


_________________
Tony
You can look at my projects here www.sambuchi.net

[Sambuchi]

well, I am not sure what happend..
I had the tv on and was exhibiting the "one line problem". Uncrewed the top 2 screws and started to pull back the case.. pulling it back a 1/2 an inch the screen popped back! I let it sit.. it went back to one line.. move the case out some more.. comes back.

So then I removed the case completely.. what a dust trap!

Hit the components with a air gun touched all the connectors..

it works fine.

Guess I will let tv sit with the 2 screws undone for now.. maybe I will get another year out of this thing!

Thanks for the input.
_________________
Tony
You can look at my projects here www.sambuchi.net

[haklesup]

That's exactly what you would expect from a solder joint failure. Since solder is very soft, it dosen't take much force to reestablish continuity by mashing it back together. Expect the problem to return eventually.

You really need to inspect the PCB wiht a magnifying glass while flexing the board and pressing on the components and looking for any movement in the soldered pins. The PCB is either attached to or slotted into the case, any mechanical movement would flex the board and in your case, reconnect the open. Given the sensitivity to movement, I would still look at the larger components and anything near the edges of the PCB.