Franc Zabkar schrieb:
On Mon, 21 Jul 2008 17:19:16 +0200, markus wolfgart
put finger to keyboard and composed:

Hi NG,

I'm looking for some repair hints for the mentioned tv model.

The Display stay black after power on without sound displaying the last
selected channel number.
I had precautionary changed all electrolytic capacitors in the power
supply after this first occurance of the mentioned symptom but had
not really found a bad cap with high ESR during this replacement.
Thinking all should now be ok, I was able to watch tv for the rest
of the day, but after turning on the tv on the next day I get the same
behavior as previously mentioned.

It's look like a problem of the remote control receiving unit.

Does the TV respond to the front panel controls? Some sets will turn
on when the CH-UP/CH-DOWN buttons are pressed. Others will turn on
when the main power switch is turned on. Pages 2 and 3 of the circuit
diagrams (see below) show a "POWER SW" signal which appears to provide
this automatic power-on function. Otherwise check whether the uP is
sending a "POWER ON/OFF" signal to your PSU (pin #2 of 5-pin
connector).

I will start today again my investigation but in the case not having
success it would be helpful for me to read your opinion on this topic.

Many thanks in advance for any help

Markus

Here are the circuit diagrams:
http://www.eserviceinfo.com/download.php?fileid=892

- Franc Zabkar
Hi Franc,

thanks for quick reply.

The tv don't respond to the channel keys but display the last channel
number from the previous run.

Today I had found some datasheet from parts located on the mainboard.
(2SD1878, 2SC2621E, TDA4940, TDA4944, AN5836, AN5860, LA7210, LA7220 and
LA4445) for my later on investigation.

Unfortunately the parts named uPC1488H, TA8659AN Toshiba, OEC8024B
Orion, and ?K1006? Sony IC102 had no positive hit by my search query :-(.

I had already found and download the schematic, but its hard to read it
as it is a very poor quality scan.

No chance to read the voltage levels and even the part id.

If you have a better scan or pdf doc, please sent it to me, if possible.

I had not yet measured the supply voltages as after the replacement of
all power supply caps located nearby a heat causing part the tv was
running the whole evening like usually. After power down and power on
the next day I got a black screen again and only the channel LED was on.
(no audio tone, no noise on the screen). No respond on pushing the
channel keys at the front panel.

I had checked the remote control transmitter led with a digital camera,
looks fine, ir led is flashing the RC5 patterns when pushing a key.

In addition you right my tv model has to be started by the remote
control main button when powered on starting on the last channel selected.

I hope to have more luck today to find the reason for malfunction,
but its more complicated when I had to check signals on a running tv
bacause of missing service manual.


Greetings

Markus

DL8MBY