Hello All, So I am working on the PSU of said tv, got it free, opened it up, saw 4 or 5 obviously swollen caps and a blown AC main in fuse T8AH250v. Inspected all components and have found no visibly damaged parts. When I removed the 2 large voltage caps 270uf 450v found one to be slightly melted on positive leg and both rattled when shaken.
So ordered new fuses and all caps, replaced every electrolytic on the board and the fuse with correct series and ratings and polarity. Powered on through light bulb tester, with only ac voltage applied, no other cables connected to PSU.
Now PSU clicks every second, when it clicks the light bulb flashes bright then back to dim. But does not blow the fuse. So have a short somewhere. There is no schematic that I can find to help troubleshoot.
During the time supply is plugged in and clicking, it has the following Stable voltages with no fluctuating to relays clicking.
5vStby = +5.3v
5vSW = +5.2
12vssb= +12.2v
VA Supposed to be 55-65v = +5.9v
The vs_on pin goes high 3.2v to low 1.2v or so in time with relay clicking, meter is a little slow to read precise volts though. No other voltages present + or -.
Now for the strange part, the fault led on the board is on solid not flashing any code. The codes are printed on PCB.
So upon further testing found a 5 band resistor on ac in side connected across Neutral and Load traces before the thermistor to read open with meter. Removed from circuit and retested. It has violet,green, yellow, gold, green bands.
I used Digi Key's resistor calculator to determine it is supposed to be a 75.4 ohm 5%. Tested with meter reads nothing until put on 2000kohms. it then reads 756kohms. It also reads the same on the cheap ESR tester I got off ebay.
I am thinking its bad, supposed to read 75.4 ohms or so with meter set to 200ohms. Am I correct? Sorry for the long post, but I have tested almost everything on the board for shorts and have not been able to find any.
All fets, diodes and main rectifier test ok in circuit. Thanks.
So ordered new fuses and all caps, replaced every electrolytic on the board and the fuse with correct series and ratings and polarity. Powered on through light bulb tester, with only ac voltage applied, no other cables connected to PSU.
Now PSU clicks every second, when it clicks the light bulb flashes bright then back to dim. But does not blow the fuse. So have a short somewhere. There is no schematic that I can find to help troubleshoot.
During the time supply is plugged in and clicking, it has the following Stable voltages with no fluctuating to relays clicking.
5vStby = +5.3v
5vSW = +5.2
12vssb= +12.2v
VA Supposed to be 55-65v = +5.9v
The vs_on pin goes high 3.2v to low 1.2v or so in time with relay clicking, meter is a little slow to read precise volts though. No other voltages present + or -.
Now for the strange part, the fault led on the board is on solid not flashing any code. The codes are printed on PCB.
So upon further testing found a 5 band resistor on ac in side connected across Neutral and Load traces before the thermistor to read open with meter. Removed from circuit and retested. It has violet,green, yellow, gold, green bands.
I used Digi Key's resistor calculator to determine it is supposed to be a 75.4 ohm 5%. Tested with meter reads nothing until put on 2000kohms. it then reads 756kohms. It also reads the same on the cheap ESR tester I got off ebay.
I am thinking its bad, supposed to read 75.4 ohms or so with meter set to 200ohms. Am I correct? Sorry for the long post, but I have tested almost everything on the board for shorts and have not been able to find any.
All fets, diodes and main rectifier test ok in circuit. Thanks.
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