Dear Frank,
many thanks for your kind help and your repair hints.
I have not so much experience on repairing tv's as it's not
my daily business, but the few tv's I had already successfully
repaired in my life had mostly blown semiconductors (hv psu switching
transistor, some of them had broken diodes) or bad because overheated
electrolyt caps. I had never make the experience of malfunctioned
resistors. So your information is for my a new lesson in repairing
tv equipment. On the first view I had not found any scorched resistor
but I will try to measure them all located in the place you mentioned.
As I'm tomorrow and on Friday on a business trip, I will continue
my repair action on Saturday and will write my report on Sunday.
Goodby
and until
Sunday
Markus
Franc Zabkar schrieb:
On Tue, 22 Jul 2008 10:05:11 +0200, markus wolfgart
put finger to keyboard and composed:
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, ...
That's a vertical output. I wouldn't be looking there.
... TA8659AN Toshiba, OEC8024B Orion,
... and ?K1006? Sony IC102 had no positive hit by my search query :-(.
CXK1006L Serial Electrically-Erasable PROM (EEPROM) - With
Seq/Controller
http://www.datasheetarchive.com/specsheet/CXK1006L.html (specs)
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.
These look similar:
http://www.eserviceinfo.com/download...rion_5150.html (5150)
http://www.eserviceinfo.com/download...lor%20513.html
http://www.eserviceinfo.com/download...lor%20513.html
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
I'd be looking for an open "startup" resistor. As you say, the
circuits are hard to read, but these resistors are usually around 100K
or more, and are often connected to the base of the chopper
transistor. In your case the chopper is inside a 5-pin STR regulator.
I would check R503 and R504 (220K) at pin 2 of this IC.
Check that the OEC8024B microcontroller is attempting to switch on the
PSU by monitoring the "POWER ON/OFF" signal (pin #2 of 5-pin
connector). If that signal is toggling, then you can confine your
troubleshooting to the PSU (and the loads on the secondary side).
- Franc Zabkar