Dynex DX-22LD150A11 no pix no sound

[jalinsta]

My grandaughter,s Dynex tv was dead. Replaced SG6742 in power supply.
Now have 12v, 5v, red led comes on and changes to blue but nothing else works. There is no voltage on BL_ON, no voltage on Dim, 0.2 v on AC-OFF-detect. 5Volt regulator on main board is good. no sound, no pic, no backlight. No back light is out because one winding is open in the inverter xformer.
The tv went out during a thunder storm. There is no visable evidence that it was hit by lightning. Fuse was not blown. How can i check the screen, if it is bad, it will not be worth repairing. Recommendations ?

[CapLeaker]

Re: Dynex DX-22LD150A11 no pix no sound

Check PSON signal from main board to PSU

[jalinsta]

Re: Dynex DX-22LD150A11 no pix no sound

Thanks for your reply to my post. I have some knowledge on repairing CRT type tv,s but no experience repairing LCD tv,s. I don,t find any markings on the main board or power supply to indicate where i can find the PSON signal. In relationship to CRT TV,s, what is PSON and where can i find it. Is it AC or DC signal. I do not have a schematic.
I have a scope if needed.

[jalinsta]

Re: Dynex DX-22LD150A11 no pix no sound

PSON must be called BL-ON on Dynex tv,s. This signal is 3.2 v. I have 12v on the power supply going to a 5 volt regulator on the main board. Have 5 v out of the regulator to the main board.

[budm]

Re: Dynex DX-22LD150A11 no pix no sound

Dynex probably uses STBY for PS-ON (>2.5VDC = ON, <1V = OFF), the PS-ON is for turning on the rest of the power supply cicuits., the BL-ON is for turning the backlights circuit/backlcks, >2.5VDC = Backligts ON, <1V = Backlights OFF, DIM is the backlights dimming control, it can be analog 1V~5VDC typical, or PWM.
How about uploading good clear pictures of the boards so we can see how they are connected together.

[jalinsta]

Re: Dynex DX-22LD150A11 no pix no sound

7 Pictures uploaded, attached.

[CapLeaker]

Re: Dynex DX-22LD150A11 no pix no sound

These pictures need to be a straight shot. For example, we are interested on that power supply picture top left there is a connector. Can't read the pinouts as the cable is hiding them.
Anyhow provide the measurements we asked for so we can figure out what board has trouble.

[jalinsta]

Re: Dynex DX-22LD150A11 no pix no sound

Power supply connectors attached. When turned on the pilot led goes from red to blue.
Pin 1. DIM - -0.01 vdc
BL_ON - 0 vdc
Lamp-Err - 0 vdc
12 terminals - 12.13 vdc
5VBS - 5.0 vdc
AC_off_Det - 0.19 vdc
Power supply has 4, 2 pin sockets where plugs from the screen plug into.

What value is the high voltage that goes to the screen for the backlight.
Thanks for your help.

Jack

[budm]

Re: Dynex DX-22LD150A11 no pix no sound

Main board is not sending the command signal (BL-ON) to turn on the backlights circuit, no dimming control signal either.
'AC_off_Det - 0.19 vdc' This one I am not sure if it is normally HI, or normally LO.
Backlights lamp striking Voltage can be from 1500~2500V, and running Voltage can be from 1000~1500V all depend on the lamp size. Do not try to measure the Voltage with your DMM.
'No back light is out because one winding is open in the inverter xformer' If one of the two High Voltage winding is open, you still should see the backlights flash on for seconds before the protection circuit kicks in.