Riddled TV Repair Forum

jimroberts0860 · Joined: 09 Dec 2009 Posts: 11 Location: TN

i have a 37 inch sylvania lcd tv that is blowing the 4a fuse on the power/inverter board. i have taken out all the caps and diodes and all tested fine. i am very new at this (most of my experience comes from putting cap kits on arcade monitors), so any help is appreciated.
model number: lc370ss9
board number: ba8agaf0103
is it possible for the diodes in the rectifier to test okay but fail under a load? should i go ahead and change them? thanks again for any help.

Google

Jesse Mack · Joined: 22 May 2008 Posts: 600 Location: The Last Frontier

The power supply/Inverter is only part of the power supply. There is a large Red & black wire from the inverter to the power supply and you probably have a shorted regulator on the main power supply.

Jesse

jimroberts0860 · Joined: 09 Dec 2009 Posts: 11 Location: TN

it blows the fuse on the inverter even when it isn't connected to the other board. that's what made me think it was localized to the inverter. is that an incorrect assumption? you are far more knowledgeable on the subject than myself i'm sure. could it be one of the regulators on the other board? also, could the diodes in the rectifier test fine will pulled out and then fail when under a load? thanks for your time. it is truly appreciated.

Jesse Mack · Joined: 22 May 2008 Posts: 600 Location: The Last Frontier

SA1901 or Q1930 and Q1931 can blow fuses.
Do this, Unplug set, measure directly across the AC line cord using RX1 of your meter. If you read a short your surge protector is most likely blown. You can unsolder one end of the surge protector (SA1901) and measure across the protector. It should read almost infinity..

If it is shorted you can plug the set in without the protector in place and the set will operate.

Hope this helps

Jesse

jimroberts0860 · Joined: 09 Dec 2009 Posts: 11 Location: TN

so the tv can operate temporarily without sa1901? do i need to bridge the connection? thanks a lot man. i've read a lot of other posts on here and it is very cool of you to try and help so many people. thanks again.

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Jesse Mack · Joined: 22 May 2008 Posts: 600 Location: The Last Frontier

This component is a surge suppressor. Its purpose in life is to deliberatly short out in the case of a surge thereby blowing your house breaker thereby protecting your set from severe power surges. Under normal condition's it does nothing. It should measure open, so if you jumper across it you are guaranteed to blow the fuse as it is directly across the AC line.
Many times, if there is indeed a power surge, they will self destruct in the process and remain shorted theryby blowing fuses.

Clear as Mud Smile

Jesse

jimroberts0860 · Joined: 09 Dec 2009 Posts: 11 Location: TN

sa1901 wasn't the problem i guess. i just went ahead and removed it and tried a new fuse and it blew. i guess i'll move on to Q1930 and Q1931. is there any way to test these guys with a standard dmm, or do i just need to buy them and swap. keep in mind i have very little experience. also i have another tv that is almost identical that is going into protect mode after coming on and saying"digital television". i started another post about it. any idea where to start with it?

Jesse Mack · Joined: 22 May 2008 Posts: 600 Location: The Last Frontier

What is your resistance across the AC line with the set unplugged and a good fuse installed.

Jesse

jimroberts0860 · Joined: 09 Dec 2009 Posts: 11 Location: TN

.909 meg-ohms...that sound right? taking my measurement from the ends of the connection points for the power cord.

Jesse Mack · Joined: 22 May 2008 Posts: 600 Location: The Last Frontier

At the Junction of the cathodes of D1901 and D1902 to the junction of the anodes of D1903 and D1904. Measure the resistance.

Jesse