No OSD on Sharp TV 27H-S200 (CH27S20)

[Arnold stewart]

After resetting a breaker in the electrical box the TV worked O.K. but
with no On Screen Display. The TV is a Sharp Model 27H-S200 (CH27S20). I
ordered a new EEPROM and tried to go into the service mode. To enter the
service mode I must momentairly short TP2001 TO TP2002. Doing this with
the original EEPROM gives me a display of a black square about 4"
square. Pressing the CH up buttom displaces the square from the bottom
left corner to the top right corner. I should see S00 in service mode.
But I don't. With the new EEPROM I see half of a grey square. Of course
the problem is OSD not displaying. I now think that I may have a problem
in the OSD generator ic, preventing me from seeing the service mode.
Any comments would be appreciated.

 

[David]

What do you mean osd generator ic?
Modern tv sets have the OSD generated in the system control, aka
microcontroller, and routed into an rgb input of the jungle ic. Other times
it is generated inside the combined system control/jungle ic.

In order to generate osd the system control has several "Must Haves" that
need checked first. Good solid and clean Vcc, no problems on any clock or
data line, h-sync pulse, v-sync pulse, and most importantly the 60hz ac
clock signal that is generated from the AC line directly and is usually
passed through an optoisolator, to a transistor clamp circuit or similar.

David

"Arnold stewart" <arnold.stewart@sympatico.ca> wrote in message
news:g1GPb.15468$U77.1145352@news20.bellglobal.com...

After resetting a breaker in the electrical box the TV worked O.K. but
with no On Screen Display. The TV is a Sharp Model 27H-S200 (CH27S20). I
ordered a new EEPROM and tried to go into the service mode. To enter the
service mode I must momentairly short TP2001 TO TP2002. Doing this with
the original EEPROM gives me a display of a black square about 4"
square. Pressing the CH up buttom displaces the square from the bottom
left corner to the top right corner. I should see S00 in service mode.
But I don't. With the new EEPROM I see half of a grey square. Of course
the problem is OSD not displaying. I now think that I may have a problem
in the OSD generator ic, preventing me from seeing the service mode.
Any comments would be appreciated.