Panasonic TX-50EM6B LCD TV switches on OK and after about a minute switches to stand by and the red led power light flashes once every 3-4 seconds

Sounds like you power supply board needs to be replaced.

When an abnormality has occurred to the unit, the protection circuits operate and set the unit to stand by mode. At this
time the defective block can be identified by the number of blinks of the Power LED on the front panel of the unit.

Fault maybe on the A board 3.3V SOS give me your email & i send you the full timing chart.

ok, this may be a silly question but when you turn it on and it starts flashing red, have you tried pressing the stand-by button on the remote. if a tv has been put on stand-by by the remote, and is then switched off by the set, when the set is turned back on it is still in stand-by mode and you need to press the stand-by button on the remote.
other than that I don't know.

Power LED Blinking timing chart
When an abnormality has occurred the unit, the protection circuit operates and reset to the stand by mode. At this time, the defective block can be identified by the number of blinks of the Power LED on the front panel of the unit.
blinking

1 dg board, (stv 5v sense time out)
2 d board
3 d board
4 p board
5 d board
6 su sd sc boards
7 su sd sc boards
8 ss board
9 panel config
10 digi board-
11 pb board
12 h board
13 dg board

Tom Miller
Broadcast Eng

There could be a possible failure of the Ht circuit, check on your Ht Drive output trans, the LOT, any shorting in the HT capaciitors, short in the LT line. You will need to probe into the power side as there is a safety switch off. the microcontroller is working fine and hence trace carefully looking for damaged resistors, capacitors or transistors in the power side.

Error Indication Information
Error No. Error Information ERROR DESCRIPTION LAMP LED OSD LAMP OFF
(Note 3) (Note 4)
POWER LED TEMP LED
Note:
1.When any of the above errors has occurred, the LED will flash as shown above every 5 seconds.
2.When two or more errors have occurred at the same time, the LED will light up or flash as shown above, and then
change to another every 5 seconds in turn.
3.Warning OSD appears when the Air Filter is clogged 90%, accumulated operation time of the Lamp reaches 5000 hours,
or accumulated operation time of the Air Filter reaches 400 hours.
4.LAMP OFF: The LED will flash right after the Lamp goes off.
5.IC2301 is mounted on LCD Main C.B.A. which is included in the Projection Unit.
6.IC6001 is mounted on TV Main C.B.A.
Clogged air filter
more than 90%
15)
16)
17)
18)
1)
2)
3)
4)
5)
6)
7)
11)
8)
9)
10)
12)
13)
14)
- flashes 5 times -
every 5 seconds
IC2301(pin82) detects the clogged air filter, then indicates the
error when the air filter is clogged 90%.
Front Fan stop or
Lamp Fan stop
flashes orange
once every
5 seconds
- -
IC2301(pin12) detects the Front FAN stop or Lamp
FAN stop, then indicates the error when the Front FAN
or Lamp FAN is stopped.
Lamp Cover open
Temperature Sensor
short or open
flashes orange
twice every
5 seconds
flashes orange
3 times every
5 seconds
flashes green for
140 seconds.
flashing red for
60 seconds.
light up red.
flashes once
every 5 seconds
flashes once
every 5 seconds
flashes red for
10 minutes
flashes once
every 5 seconds
-
-
-
-
Abnormal
Temperature
flashes twice
every 5 seconds
flashes twice
every 5 seconds
- -
Request for Lamp
Replacement - - lights up
Power Ballast Error
(abnormal
Lamp voltage)
- -
flashes 3 times
every 5 seconds
Power Ballast Error
(abnormal
temperature)
- -
flashes 4 times
every 5 seconds
Power Ballast Error
(other causes) - -
- -
Request for Filter
Cleaning -
Abnormal Voltage
on 16 V line of
LCD Main C.B.A.
-
flashes twice
every 5 seconds
flashes twice
every 5 seconds
Abnormal Voltage
on 14 V line of
LCD Main C.B.A.
-
flashes 3 times
every 5 seconds
flashes 3 times
every 5 seconds
Abnormal Voltage
on 7 V line of
LCD Main C.B.A.
-
flashes 4 times
every 5 seconds
flashes 4 times
every 5 seconds
IC2301(pin76) detects the Lamp Cover Unit condition
(open or close), then indicates the error when the
Lamp Cover Unit is open.
IC6001(pin85) detects the Duct FAN stop, then
indicates the error when the Duct FAN is stopped.
IC2301(pin74 and 75) detects open or short of the Temperature
Sensor (R2911) on Front Thermistor C.B.A., then indicates the
error when Temperature Sensor is open or shorted.
(The error is not detected for 1 minute after Lamp ON.)
IC2301(pin74 and 75) detects the temperature attached near
the Front FAN by the Temperature Sensor (R2911) on Front
Thermistor C.B.A., then indicates the error when the
temperature becomes more than 43 C (109 F).
(The error is not detected for 1 minute after Lamp ON.)
IC6001(pin86 and 87) detects open or short of the
Temperature Sensor (R2901) on Lamp Thermistor C.B.A.,
then indicates the error when Temperature Sensor is open or
shorted.
(The error is not detected for 4 minutes after Lamp ON.)
IC2301(pin74 and 75) detects the temperature attached near
the Lamp by the Temperature Sensor (R2901) on Lamp
Thermistor C.B.A., then indicates the error when the
temperature becomes more than 60 C (140 F).
(The error is not detected for 4 minutes after Lamp ON.)
IC2301(pin11) detects the error of LCD Power C.B.A.,
then indicates the error when the temperature fuse
(117 C)(243 F) in LCD Power C.B.A. is open.
IC2301(pin11) detects the error of LCD Power C.B.A. and Lamp,
then indicates the error when an inner malfunction of LCD Power
C.B.A. occurs, the Lamp voltage becomes more than 130V or
less than 30V, Lamp current becomes more than 5A, or the Lamp
is cracked.
IC2301(pin11) detects the error of the Lamp, then indicates the
error when the Lamp is short-circuit.
IC2301(pin48) detects +16V line voltage on LCD Main
C.B.A., then indicates the error when the voltage
becomes less than +13V.
IC2301(pin47) detects +14V line voltage on LCD Main
C.B.A., then indicates the error when the voltage
becomes less than +11V.
IC2301(pin45) detects +7V line voltage on LCD Main
C.B.A., then indicates the error when the voltage
becomes less than +5.7V.
IC2301(pin44) detects +3.3V line voltage on LCD Main
C.B.A., then indicates the error when the voltage
becomes less than +2.5V.
flashes 3 times
every 5 seconds
flashes 4 times
every 5 seconds
Abnormal Voltage
on 3.3 V line of
LCD Main C.B.A.
-
-
-
- flashes 5 times
every 5 seconds
Forced cooling
The failure of Lamp
light up
-
Temperature Sensor
short or open
-
-
Abnormal
Temperature
Duct Fan stop -
When accumulated operation time of the the Lamp reaches
5000 hours, OSD (replacing the Lamp) appears on the screen.
Note: The Lamp time is stored in EEPROM (IC2305).
When accumulated operation time of the Air Filter reaches 400
hours, OSD (cleaning the Air Filter) appears on the screen.
Note: The Filter time is stored in EEPROM (IC2305).
During forced cooling, this indication is indicated.
IC2301 (pin11) detects the failure of light up processing of
the Lamp, then the POWER LED is changed as follows.
1) POWER LED flashes green for 140 seconds (while turning on).
2) POWER LED flashes red for 60 seconds (while cooling).
3) POWER LED lights up red (standby).
Note: If the Lamp will not light after attempting turning on the
power 2 or 3 times, the Lamp, the LCD Power C.B.A. or the
LCD Main C.B.A. may be defective.
Error Symptom Problem Possible Solutio

U have sound at all?Yes,than ur LCD INVERTER backlight board it dead.If power LED light keep flashing nothing on,sound or picture.Than the power supply board is dead.Must replaced the power supply board.Tries Websites Shopjimmy.com,Ebay.com to buy these refurbish boards.

thats pretty normal, it takes a good second or two to warm up and the display to turn on(at least0, you get the green flashes as you hold for on, 1 sec is a long time at times, lol, be patient, no problem with your tv!

Warranty time. The TV most likely went into protection mode because a part went bad inside.
I would take it back to the store and exchange it for a new one. 90 day warranty policy.
Have them test the new one to make sure it works so you don't have to waste another trip.
Good Luck

having problem with sony television the screen when its turn on no images found just found red color on the screen..