Expert: cleggsan - 7/5/2009

Question
QUESTION: TV shuts off intermittently and will not respond to remote or buttons on tv. Power light comes back on, and the tv will show the last channel window but otherwise black screen. It requires unplugging for several minutes to reset, then works ok until it happens again, maybe a day, or week or month later. No storms or malfunctions of other electrical items in house.

ANSWER: It is most certainly an errant power supply or some subsection of the main power supply.  It generally requires replacement of a rectifier, zener or some part of the regulating system.  Cost of repair is likely to be in the range of $200 if you can lug it in to the shop; more if they must come to your residence.

Hope this helps.
C



---------- FOLLOW-UP ----------

QUESTION: Thanks for the reply.
This tv is 6 months old.
Also, since it can work for a month without symptoms, will service be able to dx the problem if it is not actively malfunctioning?
Lastly, one sevice center said that since I have to unplug to reset, it is called "board lockup" and this means a bad board. They said power issues don't usually cause non-resonse of the controls, but rather repeated shut-offs and functional controls. Do you think this is a possible solution, and, again, can this be tested if not actively malfunctioning?

Answer
A good tech can find out what is wrong with the set.  The power supply has a protection mode which causes the shutdown.  Also, there is a memory chip that a Sharp repair center can connect to and read out the fault history.  A shop that talks about replacing a board is not a good place to go to.  You need a shop that can isolate the malfunctioning parts and replace the part at the circuit level, not at the board level.  

The term "board lockup" indicates to me they are not a component level troubleshooting shop, but they are just board replacement jockeys.  You may want to talk to a couple other service centers.

Try this site for a repair shop near you:

http://www.tvrepairpros.com/

Best wishes,
C