LG DR389 dvd with Dim display

[Grunder]

Hi, LG DR389 dvd with dim display. Cap C122 1000uf 16v (5.3v rail) was "puffy" replaced. no result. Ribbon cable to front controls/ display (see photo) pin 8. marked 5.3volts measures 5.3volts. Pin 17 marked -29volts measures -25.7 volts. replaced C129 47uf/50v (-29v rail). Voltage still 25.7 volts. Soldered numerous possible o.c. print on front controls. No result.

[Grunder]

Re: LG DR389 dvd with Dim display

obviously done something wrong- no photos - will try again

[Grunder]

Re: LG DR389 dvd with Dim display

photos LG DR389 dvd dim display

[Grunder]

Re: LG DR389 dvd with Dim display

Guess if you select 8 photos, and then click upload it will take awhile for system to digest. this time uploaded one at a time. Either PC slow or me just in a rush. Sorry, newbie at this.)

[Chungalin]

Re: LG DR389 dvd with Dim display

VFD (Vacuum Fluorescent Display) needs a large negative voltage (-29V) for enabling each segment and a low AC voltage (FD+, FD-). You can check AC at VFD pins 1-2 and 31-32 (2 outer pins, each side), all VFD are the same.

Check also C120 (AC).

Service Manual available at ElectroTanya.

[Grunder]

Re: LG DR389 dvd with Dim display

Thanks Bro, will check it out tomorrow when i come in.

[Grunder]

Re: LG DR389 dvd with Dim display

Thanks Chungalin, downloaded diagram and found the 3v3 zener was short circuit. replaced but it didn't solve the problem (see attached photos)

1) On the diagram the voltage at the transformer is marked -25 volts, a bit further on it is marked -29 volts. It measures -25.6 volts wrt gnd (which one is right?)

2) Arrows point to D134 and call it D128. On the pcb its numbered D134.

3) FD+ with respect to FD- : measures +5.5volts.

4) FD+ with respect to ground: measures -19.2volts.

5) FD- with respect to ground: measures -22.8volts
The difference between FD+ & FD- = 3.6v (Zener ZD151 = 3.3v)

6) R170 measures 99.56kohm marked as 100kohm so okay.

7) Resistors 158 161 162 160 (68 ohms) in parallel combined value 17 ohms.
Is this some kind of adjustment as the display gets dimmer/ brighter?

8) Concerning point 7) I bridged out the resistors and the display does get a bit brighter (i've removed the bridge.)

9) C120 & C129 & C122 (originally puffy) have been replaced. The Zener BZX84 3v3 was replaced with a regular radial zener.

10) The chopper transformer was removed during repair to make life easier.

The display is still not bright as it should be. Will go with point 8) if no other resolve. I feel this repair is a real waste of time. (W.O.F.T. Waste Of "F" Time).

[Grunder]

Re: LG DR389 dvd with Dim display

Hi, Job closed and returned insufficient service information. All pieces for the generation of FD- & FD+ & -29v rail have now been replaced with no resolution. Boo Hoo