Sinotec 51" Plasma Model STP-51HD20 No buttons and remote working

[angelos]

Hi all,
I ordered this sets power supply since it was blown, installed the new second hand PSU, set started up with a no signal message but now no keypad button does anything and the remote also has no effect.
I have checked the following,
1. Remote transmits using a remote tester but cant prove that its transmitting correct data. Scoped on IR on main and have got pulses.
2. When pressing the keypad you see a voltage change on the relevant K0 or K1 input (check photos) going from 5V to 3.8V to 2,3V etc
3. I warmed up the board to help any electrolytics but no change.
4. 5Vs on the keypad connector on the main has got 5.2V
5. I felt the temperature on the TSUMV59XES-Z1 and within 5 minutes was a roasty 58 degrees celsius or 136.6 Fahrenheit (Dont know if its normal). Is it not that IC that is generating the "No signal" banner? So then it's partly working.
All that i am left in doing is measuring the IR, K0, K1 inputs to ground to see if there is any low resistance and replace all caps on the main
Any help any suggestions would be sooooo appreciated.

[angelos]

Re: Sinotec 51" Plasma Model STP-51HD20 No buttons and remote working

Could it be a corrupt eprom?

[angelos]

Re: Sinotec 51" Plasma Model STP-51HD20 No buttons and remote working

Any help??

[dick_barton]

Re: Sinotec 51" Plasma Model STP-51HD20 No buttons and remote working

Just a thought but have you checked that the keyboard cable is firmly seated at both ends. Maybe worth checking the solder joints of the keyboard connector on the mainboard are all good and have not loosened due to the connector being disconnected/connected.

[angelos]

Re: Sinotec 51" Plasma Model STP-51HD20 No buttons and remote working

Hi Dick,
I have checked with my multi meter on the plug on the side of the keyboard and i get my +5V supply. I see pulses on the multi meter when i press on the remote and aim it at the sensor. I also have observed different voltage levels on K0 and K1 keyboard inputs as i press one of 6 buttons on the keyboard. Both keyboard and remote do not respond at all.
To measure this entering the CPU would be difficult as the chip pins are so close to each other. Anything else i can do?
I will re seat the cable going from the keyboard to the main board

[budwich]

Re: Sinotec 51" Plasma Model STP-51HD20 No buttons and remote working

without power on, use resistance measurements to trace and check tracks running to the appropriate devices/pins... then there is no reason to worry about track spacing. This will at least check that you have path continuity.

[angelos]

Re: Sinotec 51" Plasma Model STP-51HD20 No buttons and remote working

Yes, i will also look for the Controller chip pin outs. This will make it much easier.
I am on the verge of buying another board. Tell me, can a corrupt eprom cause such a symptom?

[R_J]

Re: Sinotec 51" Plasma Model STP-51HD20 No buttons and remote working

Yes a corrupt eeprom can cause that, it all depends on where in the program the corruption is. If it does'nt loo at the switch input status, pushing the buttons will have no effect. or if it does see the switch status it might not know what to do next, like output the power on signal to the power supply.
Sometimes, you can freeze the eeprom and it will start to work, unplug the tv, then freeze the eeprom, plug in the tv and try turning it on, sometimes that works indicating a bad eeprom chip, which in some cases can be read and programed to a new ic. But not allways, but usually worth a try.

[angelos]

Re: Sinotec 51" Plasma Model STP-51HD20 No buttons and remote working

I am gonna try that, Thanks. Will revert.