[bassboy]

Are we allowed to talk about tv's here?  I hope so... 

I have a 26 inch crt tv, it does what I need it to and I'm not interested in upgrading unless I have to.  It's past warranty but not old at all and the tube is fine - picture is bright and clear as day, but it has a problem.

Lately some white horizontal lines have appeared at the top of the screen and they seem to be moving down, covering more and more screen area.  If I think back to my school daze when I was supposed to be paying attention but wasn't, I believe that this issue is caused by a fault in the vertical height circuit.

Unfortunately that's all I know, and I don't even know what that circuit looks like or where it may be located on the circuit board, how to diagnose the issue, or even if it's worth my time to bother.  I am able to find and solder bad joints, measure and replace bad components, stay safe from the high voltage risk, etc, but can't read a schematic even if I had one.

This tv is absolutely buried in a big entertainment center type unit and almost impossible to get out, so...

I'm wondering if anyone knows if this issue is easily diagnosed and worth the time to even look at, or if I should just leave it alone until the problem gets unbearable and then throw it out.  I'd hate to trash a tv due to a single failed resistor, especially when the tube is still like new.

Is this a job an amateur like me can do?  Any info is appreciated, the more detailed the better.

[thunderbrick]

All I know is that if you touch the wrong thing, even if unplugged, it can knock you out the back of your living room.  At least that's what I remember from the way-back days.

[bassboy]

Yup, that's the horizontal deflection circuit, I think that's what the high voltage section is called, where the flyback transformer and stuff are.  That can be deadly.  IIRC the picture tube is essentially a big capacitor too and can charge itself without being plugged in.

I'm not scared.  The part that scares me is removing the tv from the wall unit.  It's in a very large wall unit and can only be removed through the back, which is no small task, it's at least a 2 man job.  I only want to do it once and can't leave the room torn apart for long, so I need a good idea if I'm looking at a likely repair or if I need a replacement tv before moving anything.

[JoshK]

I don't know jack about TV circuits.   But it sounds like it *could* be a bad vertical something tube.  My best advice is to ask this question on the diyaudio.com's tube board.  There are a lot of experienced guys on there that played with TV's for decades.  They'd have a better chance of helping you determine what you want to know. 

[bassboy]

Thanks for the suggestion.  I've never been outside the loudspeaker section (and trading post) of diyaudio.  BTW, I saw you over there looking at tapped horns a couple days ago.  Fun stuff.  Tapped horns are my theme for this week.

[cryoparts]

What brand is it?  If it is an RCA, take it apart and re-solder all the tuner connections, especially the ground connections that connect to the tuner shield.  RCA's are notorious for this problem.

If it is not an RCA, a quick re-solder of the horizontal and vertical deflection IC's will probably fix it right up.

Please don't muck around in the back unless you know what you are doing.  There is more than 30kV on the tube (albeit with low current) and it HURTS when it bites you...don't ask me how I know.

Peace,

Lee

Yup, that's the horizontal deflection circuit, I think that's what the high voltage section is called, where the flyback transformer and stuff are.  That can be deadly.  IIRC the picture tube is essentially a big capacitor too and can charge itself without being plugged in.

I'm not scared.  The part that scares me is removing the tv from the wall unit.  It's in a very large wall unit and can only be removed through the back, which is no small task, it's at least a 2 man job.  I only want to do it once and can't leave the room torn apart for long, so I need a good idea if I'm looking at a likely repair or if I need a replacement tv before moving anything.

[JoshK]

Yep, that was me poking around.  JLH's project is quite interesting, but then again so are all John's projects.  He knows horns.

Lee's advice sounds reasonable to me.  But then I don't know anything about TV's.

[timind]

I'm going back in my memory but I think those white lines may be retrace lines. They are supposed to be blanked out while the beam returns to the starting point for the next frame. It is called horizontal blanking. Twenty years ago I may have been able to diagnose the faulty part.
If it were mine I'd get a new tv. The flat panels are getting cheaper all the time.

[bassboy]

What brand is it?

Toshiba.

If it is an RCA, take it apart and re-solder all the tuner connections, especially the ground connections that connect to the tuner shield.  RCA's are notorious for this problem.

IIRC that was a HUGE issue about 15 years ago.  They still haven't fixed that yet?

There is more than 30kV on the tube (albeit with low current) and it HURTS when it bites you...don't ask me how I know.

Yeah, I know.  Back in college (with help from a teacher's assistant) I used the high voltage from a tv (with a variac to adjust voltage) to charge the diaphragm in a small electrostatic speaker I made for a project.  Even that old 13 inch black and white throws out 16000V.

I'm going back in my memory but I think those white lines may be retrace lines. They are supposed to be blanked out while the beam returns to the starting point for the next frame. It is called horizontal blanking. Twenty years ago I may have been able to diagnose the faulty part.
If it were mine I'd get a new tv. The flat panels are getting cheaper all the time.

That sounds right.  I don't want to buy new if I don't have to though, I'd rather buy audio products.

[cryoparts]

They probably have rectified that tuner problem, I haven't had to fix a TV in a long time, thank goodness...

I'd try re-soldering the horizontal deflection and vertical deflection IC's, it may just fix the problem.

Peace,

Lee

If it is an RCA, take it apart and re-solder all the tuner connections, especially the ground connections that connect to the tuner shield.  RCA's are notorious for this problem.

IIRC that was a HUGE issue about 15 years ago.  They still haven't fixed that yet?

[f2a]

some white horizontal lines have appeared at the top of the screen hi
There is    one  ic for vertical out put  in your crt tv  also  you can see one capacitor with 100 mf  to 220 mf   .this is the pump up circuit/ line on top of the picture the first step is the replace this capacitor .
My job was technical manager in Panasonic tv  service for 10  .

capacitors  in v-out circuit.
In crt tv after 5 years we need to replace some  electrolyte capacitor . special in power supply- vertical –crt circuit .these capacitor some times  can pass the test  .you should  change these  parts by new .
Blanking of horizontal   line can provide by blanking  signal from v-out .there is  one connection between v-out and video out  for blank . the scoop  can use for study on blank signal
Some times happened by defect pats in v-out  some times by video parts .but don’t forget electrolyte capacitor .

[bassboy]

Thank you very much f2a!  That is the kind of information I was looking for.  I'll let you know how it turns out, but it might take awhile.

[Den]

Kudos for trying to avoid dumping a big box of toxins, but if the repair does not work out, see craigslist.org.   People who upgrade to flat panel TV's dump perfectly good CRT's every day.  A nice flat-face 27" tube can be had for $50.