Hi Folks,

My TV works fine except that it won't stay on the channel it's set to.
It keeps cycling through the channels as if the channel-up button is
being pressed. The problem is not in the remote, since it happens when
the batteries are removed from the remote and the remote is put in a
different room.

The model is Panasonic CT-20G21, a 21" box from 1996.

I have little test equipment beyond a multimeter. I am able to solder,
and I have some understanding of electronics, but no experience working
on TVs.

Please advise.

Matt wrote:
Hi Folks,

My TV works fine except that it won't stay on the channel it's set to.
It keeps cycling through the channels as if the channel-up button is
being pressed. The problem is not in the remote, since it happens when
the batteries are removed from the remote and the remote is put in a
different room.

The model is Panasonic CT-20G21, a 21" box from 1996.

I have little test equipment beyond a multimeter. I am able to solder,
and I have some understanding of electronics, but no experience working
on TVs.

Please advise.

Just a wild guess: Check the channel-up and channel-down buttons on your
TV. They should "click" when pressed. If the button is stuck down, or
the switch below the button is damaged, you probably won't feel that
"click", or it might have a "mushy" feel.

Meat Plow wrote:
On Fri, 26 Oct 2007 23:44:37 +0000, Matt wrote:

Hi Folks,

My TV works fine except that it won't stay on the channel it's set to.
It keeps cycling through the channels as if the channel-up button is
being pressed. The problem is not in the remote, since it happens when
the batteries are removed from the remote and the remote is put in a
different room.

The model is Panasonic CT-20G21, a 21" box from 1996.

I have little test equipment beyond a multimeter. I am able to solder,
and I have some understanding of electronics, but no experience working
on TVs.

Please advise.

Cover the IR window on the tv with black tape and advise.


Okay, tried that. No difference.

none wrote:
Matt wrote:
Hi Folks,

My TV works fine except that it won't stay on the channel it's set to.
It keeps cycling through the channels as if the channel-up button is
being pressed. The problem is not in the remote, since it happens
when the batteries are removed from the remote and the remote is put
in a different room.

The model is Panasonic CT-20G21, a 21" box from 1996.

I have little test equipment beyond a multimeter. I am able to
solder, and I have some understanding of electronics, but no
experience working on TVs.

Please advise.

Just a wild guess: Check the channel-up and channel-down buttons on your
TV. They should "click" when pressed. If the button is stuck down, or
the switch below the button is damaged, you probably won't feel that
"click", or it might have a "mushy" feel.

The buttons are okay. I suspect an electronic defect in the tuner.

none wrote:
Just a wild guess: Check the channel-up and channel-down buttons on your
TV. They should "click" when pressed. If the button is stuck down, or
the switch below the button is damaged, you probably won't feel that
"click", or it might have a "mushy" feel.

As I recall, years back we had a KV25XBR with a shorted channel switch
that felt just fine mechanically.

--
One meter, to within 0.0125% accuracy (off by just under .005 inches):
Three feet
Three inches
Three eights of an inch

This could be caused by what I call "MOSFET lockup". (I've seen things like
this in other products.)

With the set turned on, pull out the power plug and let the set sit for
several minutes. Then see what happens.

Check the channel up and down switches on the front panel in case one of
them is making contact. It can also be a fault in the uPC.

--

JANA
_____


"Matt" wrote in message
...
Meat Plow wrote:
On Fri, 26 Oct 2007 23:44:37 +0000, Matt wrote:

Hi Folks,

My TV works fine except that it won't stay on the channel it's set to.
It keeps cycling through the channels as if the channel-up button is
being pressed. The problem is not in the remote, since it happens when
the batteries are removed from the remote and the remote is put in a
different room.

The model is Panasonic CT-20G21, a 21" box from 1996.

I have little test equipment beyond a multimeter. I am able to solder,
and I have some understanding of electronics, but no experience working
on TVs.

Please advise.

Cover the IR window on the tv with black tape and advise.


Okay, tried that. No difference.

clifto wrote:
none wrote:
Just a wild guess: Check the channel-up and channel-down buttons on your
TV. They should "click" when pressed. If the button is stuck down, or
the switch below the button is damaged, you probably won't feel that
"click", or it might have a "mushy" feel.

As I recall, years back we had a KV25XBR with a shorted channel switch
that felt just fine mechanically.

Such things do occasionally happen. And that is why I used the term:
"Probably"...

Matt wrote:
Hi Folks,

My TV works fine except that it won't stay on the channel it's set to.
It keeps cycling through the channels as if the channel-up button is
being pressed. The problem is not in the remote, since it happens when
the batteries are removed from the remote and the remote is put in a
different room.

The model is Panasonic CT-20G21, a 21" box from 1996.

I have little test equipment beyond a multimeter. I am able to solder,
and I have some understanding of electronics, but no experience working
on TVs.

Please advise.

let's start eliminating the easy stuff. if the IR sensor is covered
and the set keeps changing, remove the back, slide out the pcb a few
inches, stay away and power up.Observe. sometimes the plastic keys on
the set deform and press the microswitches. if this does not cure it,
desolder the microswitch for ch+ and see what happens.

-B

If someone sprayed something on the screen to clean it , or kids with
something .. it could run down inside and drip on those buttons . Take
the board out and inspect .
Take care not to get shocked .