Working on a TV can be difficult and dangerous due to the high voltage circuits inside. Always remember to unplug any TV before trying to service it and if unsure of the proper procedures, seek the service of a trained professional.
I'm sorry to hear that your television is malfunctioning and I would like to assist you. From the description of the issue, it appears that the television is attempting to start up, but the fast green blink is an indication of shutdown. I would assume that the shutdown is being commanded by the micro-processor due to some type of deficiency, but the 12 code indicates no problems. Due to safety concerns, I cannot advise you on the ballast due to the voltage being well above 220 Volts, but I can say that this does appear to be a little on the low side. The current that the ballast is capable of producing can be extremely hazardous and potentially life threatening and I do not recommend working with it.
I think that we need to determine if this is the fast shutdown flash that you are seeing at the attempted turn on, or the normal green blink. If there were an issue with the ballast or the lamp, it would likely show up with a code. An issue like this should be addressed by a television technician who is familiar with this chassis and I recommend contacting a local television repair service or following this link:
Sears Home Services
, to arrange a repair appointment with a Sears Television Technician.
Please let me know if you would like any further assistance.