I recently repaired a Sabre LCT47PBKA TV and thought I would share it as I could not find anything related to this TV or its' power supply on BadCaps.
My wife recently went to visit her sister and the brother in-law sent his TV back with her in hopes that I could fix it. It was an off brand so I figured it would be a problem with the capacitors.
I connected it to power and it showed no signs of life. I take the cover off and as expected the power supply had bloated caps. I first thought it would just be a matter of replacing the capacitors until I saw the scorch mark on the plastic insulation on attached to the back of the supply. I found two burned surface mount resistors burnt up, the four current sense resistors open, and the APFC FET shorted.
Figuring out what the values of the surface mount resistors was the going to be the biggest challenge. I was trying to calculate what they should be based on the 1653A datasheet but I did not have much faith in the results. Then I happened to find a schematic that seemed to match this power supply. After making sure the values around the 1653A chip matched the schematic, I felt comfortable using the values listed for R27 and R18.
I found the surface mount resistors I needed on some scrapped power supplies I keep around for just such an occasion. I found a couple of current sense resistors that would be equivalent in value to the four original ones, and a 20N60 in my parts box. I replaced the bad capacitors with ones I had on hand, then powered it up to see if it would work. The APFC chip (1653A) was not fried and the supply worked.
I then ordered the parts I needed from Digikey to repair it properly. Before I placed my order, I looked of the rest of the TV and found the capacitors on the inverter board blown. I suspect these capacitors were what caused the power supply to work itself to the point of failure.
After replacing all the capacitors on the inverters and power supply plus the current sense resistors and 20n60 FETs, the TV came back to life. I have ran it for 48 hours straight and it worked without any problems.
I hope this helps someone else having problems with this same power supply / TV.
My wife recently went to visit her sister and the brother in-law sent his TV back with her in hopes that I could fix it. It was an off brand so I figured it would be a problem with the capacitors.
I connected it to power and it showed no signs of life. I take the cover off and as expected the power supply had bloated caps. I first thought it would just be a matter of replacing the capacitors until I saw the scorch mark on the plastic insulation on attached to the back of the supply. I found two burned surface mount resistors burnt up, the four current sense resistors open, and the APFC FET shorted.
Figuring out what the values of the surface mount resistors was the going to be the biggest challenge. I was trying to calculate what they should be based on the 1653A datasheet but I did not have much faith in the results. Then I happened to find a schematic that seemed to match this power supply. After making sure the values around the 1653A chip matched the schematic, I felt comfortable using the values listed for R27 and R18.
I found the surface mount resistors I needed on some scrapped power supplies I keep around for just such an occasion. I found a couple of current sense resistors that would be equivalent in value to the four original ones, and a 20N60 in my parts box. I replaced the bad capacitors with ones I had on hand, then powered it up to see if it would work. The APFC chip (1653A) was not fried and the supply worked.
I then ordered the parts I needed from Digikey to repair it properly. Before I placed my order, I looked of the rest of the TV and found the capacitors on the inverter board blown. I suspect these capacitors were what caused the power supply to work itself to the point of failure.
After replacing all the capacitors on the inverters and power supply plus the current sense resistors and 20n60 FETs, the TV came back to life. I have ran it for 48 hours straight and it worked without any problems.
I hope this helps someone else having problems with this same power supply / TV.
Attached Files