Hello gurus out there ,i got a Sanyo LCD TV with no sound and no picture...when turne on the blue indicator light comes on directly,checked voltages on power supply board i get the 5v ,when connected to the main board with the inverter disconnected i get all the required voltages that is 5v 12v and 24v going to the inverter board and the to indicator from red turns to blue when activated on the remote....the moment the inverter board is connected and the tv is turned on i get 24v and then immediately it discharges to 0v..not sure if its the inverter or the power supply or the main board. What can cause the 24v to drop instantly when tv is turned on. Cheers.

 

Hello there,

Modern TV's are somewhat complicated, but in spite of this i was able to fix one of mine by replacing the low voltage electrolytic capacitors.

The symptom was the same. The TV would seem to power up, but would turn right off before i could get any picture.

This also happened with a computer power supply i had where the computer would randomly turn off by itself and the problem got progressively worse as time went on.

Both of these problems were solved by replacing the electrolytic caps, mainly the ones that were for the high or medium current low voltage supplies. In some cases i could see brown stuff that came out of the top or bottom of the caps. The cases were almost always bulged out at the top as they are made to do that if there is too much internal pressure. Typical values are 1000uf and 2200uf and are typically used to filter the 5v, 12v, 15v, or 20v supplies so they would have low voltage ratings like 10 to 30v or so. The high voltage caps (200 volt ratings) always seemed to be ok.

So check the electrolytic caps as all of them have limited life spans. That could be the answer. Of course there are a lot of parts that could go bad in these things so there is no guarantee that it is definitely the caps, but it's worth a shot.

 

Hello there,

Modern TV's are somewhat complicated, but in spite of this i was able to fix one of mine by replacing the low voltage electrolytic capacitors.

The symptom was the same. The TV would seem to power up, but would turn right off before i could get any picture.

This also happened with a computer power supply i had where the computer would randomly turn off by itself and the problem got progressively worse as time went on.

Both of these problems were solved by replacing the electrolytic caps, mainly the ones that were for the high or medium current low voltage supplies. In some cases i could see brown stuff that came out of the top or bottom of the caps. The cases were almost always bulged out at the top as they are made to do that if there is too much internal pressure. Typical values are 1000uf and 2200uf and are typically used to filter the 5v, 12v, 15v, or 20v supplies so they would have low voltage ratings like 10 to 30v or so. The high voltage caps (200 volt ratings) always seemed to be ok.

So check the electrolytic caps as all of them have limited life spans. That could be the answer. Of course there are a lot of parts that could go bad in these things so there is no guarantee that it is definitely the caps, but it's worth a shot.[/QUOT


Hello Mr AL,

I did replace the smaller caps but the ones you mentioned were looking fine no bulges from the top or side,no visible leakage,its very strange when the inverter board is disconnected the 24v is present ,but when it is connected to the power supply i can see the volts drop from 24 to quite low status(with the help of my DMM) .will try and replace all the other caps on the lips board and see what happens .thank you very much for your reply cheers.

 

Hello there,

You are welcome,and i hope you can find out what is wrong.

A small note:
When you typed your message you had typed within the quotes from the quoted message so it came out as one big quote with no following message. Here is a quote of your message:

Hello Mr AL,

I did replace the smaller caps but the ones you mentioned were looking fine no bulges from the top or side,no visible leakage,its very strange when the inverter board is disconnected the 24v is present ,but when it is connected to the power supply i can see the volts drop from 24 to quite low status(with the help of my DMM) .will try and replace all the other caps on the lips board and see what happens .thank you very much for your reply cheers.

 

Along with the capacitor issue (most common) you can also get a backlight fault, which over drives the invertor, pulls too much current and causes the power supply to get stuck in a fault state.