Vertical Collapsing TV Screen

[drew]

Hi,
I have an 8 year old 27inch JVC television (AV27750) and I think the problem
I have is a vertically collapsing screen. Basically, the tv is working great
then, after a minute or so, the screen flickers and then the top and bottom
"collapse?" until there is but a thin white line, running horizotally across
the middle of the screen. Is this something I might be able to fix? I love
little projects like this, but I have never worked inside TV's before and I
usually destroy things that I try to solder myself. The TV would just end
up on the curb anyway, so I thought I might as well get out the ole
soldering iron... Are there any good resources to check out to be able to
figure out which part is bad and how to get started? Thanks for any advice.

Drew

 

[David]

Resolder the vertical circuit should fix it. Given your tendency to destroy
things you try and solder, better to give it away or pay for the expected
$75 to have it repaired by someone with experience.

David

 

[Steve(JazzHunter)]

Hi,
I have an 8 year old 27inch JVC television (AV27750) and I think the problem
I have is a vertically collapsing screen. Basically, the tv is working great
then, after a minute or so, the screen flickers and then the top and bottom
"collapse?" until there is but a thin white line, running horizotally across
the middle of the screen. Is this something I might be able to fix? I love
little projects like this, but I have never worked inside TV's before and I
usually destroy things that I try to solder myself. The TV would just end
up on the curb anyway, so I thought I might as well get out the ole
soldering iron... Are there any good resources to check out to be able to
figure out which part is bad and how to get started? Thanks for any advice.

Drew

Defective Vertical output IC. It's running off-bias and when it heats
up it saturates, shutting down, or there's thermal protection. If
it's a single transistor then the PN junction is breaking down when it
heats up, though the latter circumstance should produce more
unpredictable failure. Look for an IC on a heatsink not too close to
the HOT and Geometry coils, but not on the other side of the set near
the Power cord connector, that would be the power regulator.

. Steve .

 

[crayzKirk]

Fyi,

A typical verical IC is the LA7838 and is very inexpensive to replace. It
will be mounted on an aluminum plate. It is a 13 pin inline chip. Get a
low wattage soldering iron from Radio Shack. Don't use one of those trigger
Sears types. Use the correct 60/40 rosin solder as well. A small
magnifying glass works wonders too.

Take you time and be careful. You can fix it! I've rescued two TVs; one
had a bad vertical IC and the other had a bad capacitor. The other didn't
survive yet continues to live on by giving up parts for other repairs.

Where are you located? If you are going to kick it to the curb and are in
my area, I'll save you the trouble and come get it.

Kirk

P.S. check out the repair faq (www.repairfaq.org) for more info.

 

[drew]

where are you located? If you are in my area, I'll make you come by and fix
it!

 

[Asimov]

"crayzKirk" bravely wrote to "All" (08 Jan 04 15:45:17)
--- on the heady topic of "Re: Vertical Collapsing TV Screen"

cr> From: "crayzKirk" <[email protected]>

cr> Fyi,

cr> A typical verical IC is the LA7838 and is very inexpensive to replace.
cr> It will be mounted on an aluminum plate.

Also add on the biggest heatsink and grease that will fit... those
LA7838 get hot in such a small package often with inadequate cooling!

.... No electrons were harmed in the posting of this message.

 

[crayzKirk]

Drew,

Kansas City, MO

You?

Kirk

 

[Jason D.]

Hi,
I have an 8 year old 27inch JVC television (AV27750) and I think the problem
I have is a vertically collapsing screen. Basically, the tv is working great
then, after a minute or so, the screen flickers and then the top and bottom
"collapse?" until there is but a thin white line, running horizotally across
the middle of the screen. Is this something I might be able to fix? I love
little projects like this, but I have never worked inside TV's before and I
usually destroy things that I try to solder myself. The TV would just end
up on the curb anyway, so I thought I might as well get out the ole
soldering iron... Are there any good resources to check out to be able to
figure out which part is bad and how to get started? Thanks for any advice.

Drew

Drew,

If the picture quality is still good even acceptable, get vertical
circuit fixed for modest cost if you leave tv unplugged till tv goes
to the shop.

That will only take one cap and resolder rest of high power resistors
for tv be reliable again. Otherwise a vertical chip is not that
expensive, appox 10 dollars.

JVC sets are not that common in many areas but they're still regarded
good sets.

Cheers,

Wizard

 

[drew]

The drive would be too great as I live in Austin, TX.

Is the LA7838 a generic chip that works in many sets? Is it not critical to
examine the particular chip in my set and buy the exact one?

Thanks for your help.
Drew

 

[drew]

My only concern about taking it to get fixed is that the bench fees are
usually around $35. The TV cost under $500 in 1996 so if the fee gets much
more than $35, it hardly seems worth it. Also, if I were to be able to
repair my own TV, think what that would do for my confidence.

Quick questions-- if I were to try my hand at this, how do I tell if the
problem is the capacitor or the IC? Or is it so common to replace both that
it doesn't matter which was the problem?

Thanks,
Drew

 

[Sofie]

drew:
The bad chip MUST be replace with the correct chip part number.

 

[Sofie]

drew:
At this point, since the television is still intermittently working, the
chip is probably not defective..... the problem is most likely dry and
cracked solder connections and maybe a few electrolytics.
This can be fixed at most shops fairly inexpensively.... as long as it is
still making a full picture intermittently...... do not wait and continue
running the television..... it will just get worse to the point that the
chip and other components may fail and the repair bill will certainly be
much higher.
Get it to a shop right away for what should be a fairly cheap repair... or
at the very least you should TAKE it to a shop to get a repair cost estimate
so you can make an intelligent repair decision with facts instead of
telephone or internet guesses. A tech will actually have to see the set and
maybe do some tests with real test equipment in order to give you an exact
diagnosis. At this point, we are all guessing about the repair cost.....
TAKE it to a shop.

 

[drew]

thanks for the help. What is a reasonable cost for this diagnostic and
repair quote?

Drew

 

[crayzKirk]

Agreed... I just named it as a common one. You will have to look at the
specifics of your set to determine which one it is. The board usually has
the various sections silk-screened on it. Just be careful around the high
tension lead on the tube. Don't touch it and it shouldn't touch you! Get a
pad of paper and pencil to note everything you take apart. A digital camera
works great for showing where all those wires go. In a week, you won't
remember what goes where if you are anything like me.

Don't work on any set that is plugged in unless you *really* know what you
are doing. Even then, you must use an isolation transformer. There are
also some large filter capacitors that can retain a dangerous charge for
some time. Again, check out www.repairfaq.org for safeguards and guidelines
for repairs.

It can be a rewarding past-time however it is more dangerous than collecting
postage stamps or rare coins...

Kirk

 

[Sofie]

drew;
You can ask the shop you take it to........ there is really no standard
price everywhere. Almost without exception the estimate fee will be
applied to the repair invoice if you go ahead with the repair so in essence,
the estimate would be "free" if all goes well. Be certain to ask about the
policies of the shop that you take it to before you leave the television.

 

[[email protected]]

thanks for the help. What is a reasonable cost for this diagnostic and
repair quote?

Drew

Call and describe your problem over the phone. They might be able to give
you a reasonable estimate for free. I had a problem with the vertical on
my JVC (the top 10% of the picture was folded over). They knew what the
problem was likely to be, estimated $75 and billed me $65. Kind of
pricey, but better than $200 for a replacemnt.

Bryan