Panasonic TV model CT-20G11U image distortion
 

Hi,

Patient: Panasonic TV, 20", I think I got it in 8 years ago. Model
number is CT-20G11U

Symptom: The top 10% part of the image is very distorted, but most of
the rest of the image is OK. I think that part of the image is
non-linear, the lines are very spaced at the very top and they are very
close at the bottom, and then the other 90% of the image is mostly
fine. This problem comes and goes in the first 10 minutes after
startup, then is stays there. The problem started one month ago, and it
seems to get worse.

I am about to go shopping for a new TV. Wife wants the same size (20",
that is the TV, not what you might think off...), I would like a
30-32", I have seen some Sanyo models with built-in HDTV tuner. But I
digress...

Back to my sick patient: before I dump it, is there any chance that I
might fit it myself? like a leaking capacitor, or an overheating
resistor, or something like that??? I am not shy to handle a soldering
iron, and I have basic electronic knowledge (i.e. I know most than 99.9
os so than most people, but I am no TV repair guru at all). I have
access to a Tektronix scope if useful, TDS3000 series.

So in a few days I am headed to the dumpster, unless one of you gurus
tells me something like "THERE IS USUALY A CAPACITOR ON THE MAIN BOARD
THAT LEAKS, CHECK C101 FIRST AND IF NOT, THEN RESISTOR 102", well, you
get the idea, if you know something, say it.

Thanks. many many thanks.

Simple, the capacitors in the vertical output circuit are going bad.
Usually the pump up capacitor and return capacitor. Take a look in the
set and find the vertical output ic on its heatsink, usually near the
crt yoke connections, find the capacitors, replace them.

Go he http://www.eserviceinfo.com/equipmen...nasonic_2.html
The ct27D10 should have a similar vertical output circuit so you can
see in schematic form the general, typical vertical output ic design.

thanks, I will give it a try and report back how it went!

Hi,

I searched Google some more and found an older post which indicates a
faulty capacitor like you said, C455. The author said it's a very
common defect, especially for circuits with IC LA78--. That's exactly
what I have in my TV! so I used a hair drier to warm up the entire area
(IC and may other components) and the defect almost goes away. Then I
used a canned air spray (upside down) to cool down the capacitor c455.
The defect came right back! it looks like the cap is the problem
indeed. RadioShak does not carry it, I have to check see if I find one
at work tomorrow or if I can take one from some old VRC or whatever I
might find laying around. I need a 35 microF / 100 V electrolitic.
Damn, I can't find one right now...

Thanks!

chibitul wrote:
Hi,

I searched Google some more and found an older post which indicates a
faulty capacitor like you said, C455. The author said it's a very
common defect, especially for circuits with IC LA78--. That's exactly
what I have in my TV! so I used a hair drier to warm up the entire area
(IC and may other components) and the defect almost goes away. Then I
used a canned air spray (upside down) to cool down the capacitor c455.
The defect came right back! it looks like the cap is the problem
indeed. RadioShak does not carry it, I have to check see if I find one
at work tomorrow or if I can take one from some old VRC or whatever I
might find laying around. I need a 35 microF / 100 V electrolitic.
Damn, I can't find one right now...

Thanks!

Hi...

Just in case you didn't know - to make your search a
little easier, that 100 volts isn't written in stone.

Anything 100 volts or higher is fine, provided that you
can mount it nicely.

Ken

right... I need 100V/35uF, but higher voltage would be OK as you said.
But... I don't have 100V right now. I actually have the opposite
problem: I can get at RadioShack some 50V capacitors, so I want to
mount two in series, let's say 68uF each. Would that work?

2 in parallel
"chibitul" wrote in message
oups.com...
right... I need 100V/35uF, but higher voltage would be OK as you said.
But... I don't have 100V right now. I actually have the opposite
problem: I can get at RadioShack some 50V capacitors, so I want to
mount two in series, let's say 68uF each. Would that work?

2 in parallel add for caps but not the voltage.
kip
"chibitul" wrote in message
oups.com...
right... I need 100V/35uF, but higher voltage would be OK as you said.
But... I don't have 100V right now. I actually have the opposite
problem: I can get at RadioShack some 50V capacitors, so I want to
mount two in series, let's say 68uF each. Would that work?

"chibitul" wrote in message
oups.com...

right... I need 100V/35uF, but higher voltage would be OK as you said.
But... I don't have 100V right now. I actually have the opposite
problem: I can get at RadioShack some 50V capacitors, so I want to
mount two in series, let's say 68uF each. Would that work?

If you add resistors in parallel. Otherwise one will have 70 volts and the
other 30 volts across it.

N

On 12 Jul 2005 20:46:22 -0700, "chibitul"
wrote:

Hi,

I searched Google some more and found an older post which indicates a
faulty capacitor like you said, C455. The author said it's a very
common defect, especially for circuits with IC LA78--. That's exactly
what I have in my TV! so I used a hair drier to warm up the entire area
(IC and may other components) and the defect almost goes away. Then I
used a canned air spray (upside down) to cool down the capacitor c455.
The defect came right back! it looks like the cap is the problem
indeed. RadioShak does not carry it, I have to check see if I find one
at work tomorrow or if I can take one from some old VRC or whatever I
might find laying around. I need a 35 microF / 100 V electrolitic.
Damn, I can't find one right now...

Thanks!

Are you sure it isn't 100uF/35VDC?

Tom

On Wed, 13 Jul 2005 20:31:32 GMT, Tom MacIntyre
wrote:

On 12 Jul 2005 20:46:22 -0700, "chibitul"
wrote:

Hi,

I searched Google some more and found an older post which indicates a
faulty capacitor like you said, C455. The author said it's a very
common defect, especially for circuits with IC LA78--. That's exactly
what I have in my TV! so I used a hair drier to warm up the entire area
(IC and may other components) and the defect almost goes away. Then I
used a canned air spray (upside down) to cool down the capacitor c455.
The defect came right back! it looks like the cap is the problem
indeed. RadioShak does not carry it, I have to check see if I find one
at work tomorrow or if I can take one from some old VRC or whatever I
might find laying around. I need a 35 microF / 100 V electrolitic.
Damn, I can't find one right now...

Thanks!

Are you sure it isn't 100uF/35VDC?

Tom

Not the same model, but...

http://www.hamradio-badarc.co.uk/tel...p/panalpa1.htm

You won't likely find one in a VCR chassis, but, if I'm right, almost
any TV chassis will have one.33uF is the standard value, not 35. Both
35 and 100 are standard voltage values.

Tom

OOOPS, you are correct Sir! My memory is fading. I am geting old...
what was I saying? back to RadioShack!!!