Power supply Hi, I took the power supply board out of the tv went home and pluged into a variac tried to measure some voltages from test points. But I could not measure anything at all. It was working while in the tv. I then traced the voltage started from where the ac goes into the board.On the white wire and it's related components always measured 7v and the black wire side goes to the fuse and all componets always measured 105v(or whatever I cranked the variac up). There's a varistor between the white/black wire.I am not sure it's good or not. My question is whether it is correct to take the board out and do service as it may not be grounded correctly. Any advices are much appreciated. Pete

Are you able to get some voltage measurements?

To find out what is going on your going to need to measure the power supply voltages and PSON voltage, start with the 5 volt supply if that is normal then test the PSON voltage it should either be 3 to 5 volt and go to about 1 volt or be close to 1 volt and go to 3 to 5 when you push the power button, if you see that change then test the other voltages. if they are all ok the power board is working ok, Be very careful around the power supply, if your not familiar with testing high DC voltage then take it in and have it repaired as the hot side voltage gets close to 400 volts on some sets.

Thunderstorm over the coax or /and the power supply measure the power supply by a defect cannot be measured anymore over an analog hand adjustable power Variac transformer from 0 to 240 volt. because a protection can be given by a defect t-con board (as suggestion) but the variac its good to bypass/ overhaul the build-in safety protection circuit inside the power supply board then sometime if there else are broken or bad components hard to find they can be sometimes intentional burning out or become warmer by twist the variac power slowly up from of zero volt until the max necessary voltage T-con boards that can have a problem with smd components sometimes they can burning out the defects but its only to do if there is no equipment to measure repair or nothing was to find without a service manual or other optical defects , an short-circuit tuner also by thunderstorm sometimes only the little ceramic capacitors what hangs to earth (chassis) if the thunder energy was coming over the antenna coax cable. the power supply can stand in a safe protection mode. then a refurbished board somewhere can be necessary that will give a reset to release the protection mode in the power supply.. Thunderstorm can be strange and much different and i have had 2 times repairing when there was only 1 ceramic short-circuit ceramic capacitor to find thats was with one leg is( on cold-earth) on the chassis. as the one and only defect component. A time in a TV and 1 time in a radio , sometimes its realy strange but comes it over the power supply its hard to find because of more recurring complaints if partial repair in smd circuits. hard to do without necessary tools.

quite possibly have defective panel, since you have replaced X,Y & buffers.

First, inspect the electrolytic capacitors on the power supply board. The top of a burned-out capacitor is often domed instead of flat. You may measure proper voltage with no load, but the bad capacitor will not support a load. (Note: the voltages are usually printed on the board next to the output connector.) The page linked below includes a nice illustration of both good and bad capacitors. Also, check the LED driver board for the same problem. If you don't see anything like that, add a comment to the post to that effect, and we'll look at other possibilities.

CapacitorLCDPARTS net

Hello,

The power light may be flashing or if you are runing with a series light bulb it may be cycling on and off continuously. There may be a chirping or clicking sound from inside the set. (Note: using too small a series light bulb load during testing for the size of the TV may also result in this condition.)

If there is a low voltage regulator or separate switching supply, it could be cycling on and off if the horizontal output, flyback, or one of its secondary loads were defective.

Does this TV have a separate low voltage regulator and/or switching power supply or is it all part of the flyback circuit? For the following, I assume it is all in one (most common).

Some simple things to try first:

Verify that the main filter capacitor is doing its job. Excessive ripple on the rectified line voltage bus can cause various forms of shutdown behavior. An easy test is to jumper across the capacitor with one of at least equal voltage rating and similar capacitance (make connections with power off!).

Use a Variac, if possible, to bring up the input voltage slowly and see if the TV works at any point without shutting down. If it does, this could be an indication of X-ray protection circuit kicking in, though this will usually latch and keep the set shut off if excessive HV were detected.

Hello,

The power light may be flashing or if you are runing with a series light bulb it may be cycling on and off continuously. There may be a chirping or clicking sound from inside the set. (Note: using too small a series light bulb load during testing for the size of the TV may also result in this condition.)

If there is a low voltage regulator or separate switching supply, it could be cycling on and off if the horizontal output, flyback, or one of its secondary loads were defective.

Does this TV have a separate low voltage regulator and/or switching power supply or is it all part of the flyback circuit? For the following, I assume it is all in one (most common).

Some simple things to try first:

Verify that the main filter capacitor is doing its job. Excessive ripple on the rectified line voltage bus can cause various forms of shutdown behavior. An easy test is to jumper across the capacitor with one of at least equal voltage rating and similar capacitance (make connections with power off!).

Use a Variac, if possible, to bring up the input voltage slowly and see if the TV works at any point without shutting down. If it does, this could be an indication of X-ray protection circuit kicking in, though this will usually latch and keep the set shut off if excessive High Voltage were detected.

Hi my name is Roety,
I can help you with your issue ,
If you have no TV menu either check for any swollen capacitors on the power supply.
If none are found measuring voltages will localize the defective board or boards the voltage test points are marked VA and VS on the panel and boards.
If disconnecting boards restores these voltages the suspected boards must be replaced .
Tech labor is about $250 plus parts.
Suspected boards
power supply
Y sus main & Y buffers 　
Logic board
mainboard
panel
　
　
If I have helped you with your issue
If you have more questions you can still respond
I will reply asap
Thanks

I’m happy to help further over the phone at https://www.6ya.com/expert/eric_ab7c09ec01841771

Good Day;
Make sure when measuring voltages that your'e on the proper ground, all TV's this day has two grounds. The HIT has #'s near the components, LED's that light or do not light. YES, get info to trouble shoot further.
Good Luck, big IRISH.

Good Day;
Make sure when measuring voltages that your'e on the proper ground, all TV's this day has two grounds. The HIT has #'s near the components, LED's that light or do not light. YES, get info to trouble shoot further.
Good Luck, big IRISH.