I have a th-42pz77u It stoped working. when its plugged in the red light blinks 13 times? the tv wont come on is this fixable?

Yes almost anything is it is simply a matter of costs and parts availability.
What is happening is the internal "Fault" that is causing the Protection Circuitry , to detect the problem and attempt to shut down the set, keeps restarting the set, because as soon as it shuts down, the "Faulty" component(s) cool down?, and the "Fault" ostensibly "Clears" so the PSU starts up again, only for the component(s) to heat up, whatever, again and fail, so it shuts down, and if left unattended, this would continue on until the part eventually failed. As related this is called a "Hic-upping Power Supply". Any fault that involves the power supply is usually quite serious, and needs a professional, usually, unless one is familiar with servicing current day, televisions.
And in my professional recommendation, you should get a "Quote" for repair, from, an, Approved Service Center. Now, this point is very important for a good result, Always contact, their "Local" or a, "Head Office" Panasonic, in your case. Ask them, for a referral to an authorised servicing center, where you ask for a "Quote". Now, when you get the information you want, then you can decide as to repair of replacement.
The reason we want an approved agent, is that way, all the engineers are trained on their own brand sets, they have seen almost all faults, and will get the job done quicker, and for less cost, and usually have parts on hand, also sometimes, there has been a service bulletin in issued and the repair may be subsided or even free. There are many, many, many reasons that display this symptom, one must work through the troubleshooting steps to isolate and identify, the Cause and repair that and any damage done.

I think there is a problem with STR. You better visit any authorised Panasonic service centre, they will solve this.