Well isn't this just a find how do you do!!
It appears that on this set there is no headset or other audio connection other then the optical?
It appears the only way to a traditional RCA audio jack is via a special adapter. See image. Inexpensive not sure of the quality of audio.
The best way would be to purchase a sourround sound speaker amp system with 5 speakers plus base woofer. These surround sound systems are usually have optical connected and for best results this would be my first choice.
Some have wireless back speakers to allow for easier installation.
RCA RT2781BE 1000W Home Theater System with Bluetooth
This unit has two optical inputs and one digital input.
This is an inexpensive surround sound speaker system that should connect to your Panasonic TV optical output. Very available and I wanted to give you at least one option. Wires etc are a mess but the surround sound can be amazing. I would check all the reviews if you decide to go with this type of audio system. They can be confusing and in your case you need to have input control of volume with optical.
The following link is the manual for this particular Home theater System.
http://rcaav.com/wp-content/uploads/2014/11/RT2781BE_IB_0708.pdf
These audio systems can be very expensive. Less expenesive sorround can still provide great listening results.
Hope this helps?
These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices. http://electronicshelponline.blogspot.com/
Sounds like you have a bad input board and it is only time before you lose three. If it is under warranty get it in otherwise start tracking down the part. Most of these are a plug and play device once the tv is apart.
Check the Input Source: Make sure you have selected the correct input source on your TV for the device you are using. Use the remote control to cycle through the input options until you find the one connected to your video source.
Check Video Connections: Ensure that all video cables (such as HDMI, component, or composite cables) are securely connected between your TV and the device you are trying to watch content from. A loose or faulty cable connection could result in a loss of video signal.
Restart the TV and Video Source: Try restarting both your TV and the device you are trying to watch content from. Power off both devices, wait a few moments, and then power them back on. This can sometimes resolve temporary glitches or issues with the video signal.
Check for Software Updates: Make sure your TV's firmware is up-to-date. Sometimes software updates can resolve compatibility issues or bugs that may be affecting video playback. Check the settings menu on your TV for an option to update the firmware, or visit the manufacturer's website for instructions on how to do so.
Reset Video Settings: If you've made any changes to your TV's video settings, such as resolution or picture mode, try resetting them to their default values. This can sometimes resolve issues with video playback.
Try a Different Device: If possible, try connecting a different device (such as a DVD player or gaming console) to your TV to see if the issue persists. This can help determine whether the problem lies with the TV itself or with the original device you were using.
Contact Panasonic Support: If none of the above steps resolve the issue, it's possible there may be a hardware problem with your TV. In this case, you may need to contact Panasonic customer support for further assistance or to schedule a repair.
Check the Power Cord: Ensure that the power cord is securely plugged into both the TV and the power outlet. Make sure there are no visible signs of damage to the power cord or the plug.
Inspect the Power Outlet: Try plugging another electronic device (such as a lamp or a phone charger) into the same outlet to verify if it is functioning properly. If other devices work fine, then the issue is likely not with the power outlet.
Check for Tripped Circuit Breakers: Check your circuit breaker or fuse box to see if a circuit breaker has been tripped or a fuse blown. If so, reset the circuit breaker or replace the fuse and try plugging in your TV again.
Test with Different Power Source: If possible, try plugging your TV into a different power source altogether, such as a different room or building. This will help determine if the issue is specific to the power source you were previously using.
Contact Panasonic Support: If none of the above steps resolve the issue and your TV still does not power on, it's likely that there is a hardware problem with the TV itself. In this case, you may need to contact Panasonic customer support for further assistance or to arrange for repairs. Be sure to provide them with details of the troubleshooting steps you've already taken.
Turn off and unplug the projector.
Locate the lamp cover on the projector.
Remove the lamp cover.
Take out the old lamp.
Insert the new lamp.
Replace the lamp cover.
Reset the lamp hours:
Press the Enter button to display the "Option" menu.
Use the 5 or 6 button to select "Lamp Runtime".
Press and hold the Enter button for approximately 3 seconds.
The "Lamp Runtime" will change to "Time Reset [Power Off]".
Turn off the power and disconnect the power cord.
Finally, plug in and turn on the projector.
Remember to consult your projector's operating instructions manual for specific details and safety precautions. How to change Panasonic vx 400 xga projector lamp change or replace (youtube.com)