chassis no: P42647-00, USA, 110V/60HZ
I'm attempting to repair a Sanyo DP42647 LCD TV, chassis no: P42647-00, ser. no: B7280916771748, assembled JULY 2007 in Mexico. My daughter reports she was watching TV from 75 ohm source, when sound quit. She turned set off to attempt to fix problem. Set turned off, but no sound or picture when switched back on. Green "system on" light is working.
Current condition and functions: I have left set unplugged for 24 hours - no change. When first plugged in, there are no standby or power indicator lite. (I don't know what is "normal" and owner's manual does not specify.) Keypad on set, or remote control are both successful at "turning on" green indicator light on botton right front of set, adjacent to IR remote sensor. Am able to cycle set "On" and "Off" with remote or keypad. I do not see any backlight at all, and am not able to detect any image by shining a bright light at front of set. (I'm not familiar with set controls or menus, so I might not know how to force an image on the screen.)
Can someone provide me to a remote key sequence that would guarantee a menu screen would come up? What part of screen/how big would menu be? Remember, I am not a regular user of this TV.
I did hook a blue ray player to "video 1" input and attempt to view it. With source playing, I turned on set, and "in the blind" selected "input" on remote about ten times. Each time looking for faint image on screen. Could not detect anything.
I have opened case and inspected all boards for visible flaws. All "can style" electrolytic caps appear normal. Don't see any bulges or leaking. Have not inspected any surface mount caps.
I believe I have done a good job to "prove" the power supply. +5V is ON all the time and is within .2 volts even when driving additional load of "type 1157 automotive stop light." (bulb is dim.) +12V and +24V switch ON and OFF to match "green power light" on front of set. +12V is within .2 volts even when driving a single automotive stop light. Hooked two stop lights in series to test +24V supply and it is within .3 volts also. The TV will stay "ON" all day, meaning correct PS voltages are present. No sound, and no picture all day too!
On the main control board, I can feel warmth on the audio amp aluminum heat sink. The 75 ohm RF input gets warm. I can't find any fuses on this main board.
I have a simple analog current meter from Radio Shack. You plug the test device into a special socket, and then "clamp" the analog meter around a 10X current coil. With the meter on 6 Amp scale, I measure steady state ON current of approx. .265 amps. I can use remote control to "turn on" TV and watch start-up currents. The analog needle does not exceed .4 AMP on initial start, and it will settle down to .265 AMPS. About 1/2 second, after initial inrush, I can see the needle give a quick pulse, then settle down.
If I disconnect the +24V supply to the inverter board, then the "tiny current pulse after 1/2 second" goes away. Also, the steady state current goes down a small ammount with the inverter board power removed. I conclude, when connected, the inverter is consuming a tiny ammount of power. I would expect higher power consumption difference if the backlights were being driven.
I found two fuses on inverter board. F100 and F500 both show zero ohms. There are four wires from the main processor board that connect to the inverter board. Is one of these the PWM dimming/brightness signal? Can a tech tell me which wire, and can I drive it with a voltage to "force backlight on?"
A total of ten fluorescent tubes are driven. If I disconnect all tubes, I measure approx. 2.5Kohm between each HOT lead at power socket to GND, and about 5.0Kohm between each pair of HIGH VOLTAGE leads. There are a total of 20 high voltage transformers. There are three input pins connected. One pin measures approx. 487 ohms to ground. The other two pins measure approx. 15.0 Mohms to GND. These measurements are consistent for all twenty transformers.
I measure +12V (switched) on T-Con board that connects to LCD panel.
Initial failure of TV was loss of all sound while watching TV, and picture stayed on initially, until set was shut down. Only recovery is green indicator light off and on by remote control or panel switch.
I need to suggestions on what to do to force a menu on the screen. That way, maybe I could see the image if I used the bright flashlight technique.
Any suggestions?
Will post pictures when I figure out how. (I have inspected both sides of all boards with a magnifiing glass, and I don't see any bad caps, blown fuses, or burnt areas.)
I'm attempting to repair a Sanyo DP42647 LCD TV, chassis no: P42647-00, ser. no: B7280916771748, assembled JULY 2007 in Mexico. My daughter reports she was watching TV from 75 ohm source, when sound quit. She turned set off to attempt to fix problem. Set turned off, but no sound or picture when switched back on. Green "system on" light is working.
Current condition and functions: I have left set unplugged for 24 hours - no change. When first plugged in, there are no standby or power indicator lite. (I don't know what is "normal" and owner's manual does not specify.) Keypad on set, or remote control are both successful at "turning on" green indicator light on botton right front of set, adjacent to IR remote sensor. Am able to cycle set "On" and "Off" with remote or keypad. I do not see any backlight at all, and am not able to detect any image by shining a bright light at front of set. (I'm not familiar with set controls or menus, so I might not know how to force an image on the screen.)
Can someone provide me to a remote key sequence that would guarantee a menu screen would come up? What part of screen/how big would menu be? Remember, I am not a regular user of this TV.
I did hook a blue ray player to "video 1" input and attempt to view it. With source playing, I turned on set, and "in the blind" selected "input" on remote about ten times. Each time looking for faint image on screen. Could not detect anything.
I have opened case and inspected all boards for visible flaws. All "can style" electrolytic caps appear normal. Don't see any bulges or leaking. Have not inspected any surface mount caps.
I believe I have done a good job to "prove" the power supply. +5V is ON all the time and is within .2 volts even when driving additional load of "type 1157 automotive stop light." (bulb is dim.) +12V and +24V switch ON and OFF to match "green power light" on front of set. +12V is within .2 volts even when driving a single automotive stop light. Hooked two stop lights in series to test +24V supply and it is within .3 volts also. The TV will stay "ON" all day, meaning correct PS voltages are present. No sound, and no picture all day too!
On the main control board, I can feel warmth on the audio amp aluminum heat sink. The 75 ohm RF input gets warm. I can't find any fuses on this main board.
I have a simple analog current meter from Radio Shack. You plug the test device into a special socket, and then "clamp" the analog meter around a 10X current coil. With the meter on 6 Amp scale, I measure steady state ON current of approx. .265 amps. I can use remote control to "turn on" TV and watch start-up currents. The analog needle does not exceed .4 AMP on initial start, and it will settle down to .265 AMPS. About 1/2 second, after initial inrush, I can see the needle give a quick pulse, then settle down.
If I disconnect the +24V supply to the inverter board, then the "tiny current pulse after 1/2 second" goes away. Also, the steady state current goes down a small ammount with the inverter board power removed. I conclude, when connected, the inverter is consuming a tiny ammount of power. I would expect higher power consumption difference if the backlights were being driven.
I found two fuses on inverter board. F100 and F500 both show zero ohms. There are four wires from the main processor board that connect to the inverter board. Is one of these the PWM dimming/brightness signal? Can a tech tell me which wire, and can I drive it with a voltage to "force backlight on?"
A total of ten fluorescent tubes are driven. If I disconnect all tubes, I measure approx. 2.5Kohm between each HOT lead at power socket to GND, and about 5.0Kohm between each pair of HIGH VOLTAGE leads. There are a total of 20 high voltage transformers. There are three input pins connected. One pin measures approx. 487 ohms to ground. The other two pins measure approx. 15.0 Mohms to GND. These measurements are consistent for all twenty transformers.
I measure +12V (switched) on T-Con board that connects to LCD panel.
Initial failure of TV was loss of all sound while watching TV, and picture stayed on initially, until set was shut down. Only recovery is green indicator light off and on by remote control or panel switch.
I need to suggestions on what to do to force a menu on the screen. That way, maybe I could see the image if I used the bright flashlight technique.
Any suggestions?
Will post pictures when I figure out how. (I have inspected both sides of all boards with a magnifiing glass, and I don't see any bad caps, blown fuses, or burnt areas.)
what did we say about hoarding too much stuff and depriving others of them?! *cough* socialism *cough* lol! 
Comment