LG RH7521W Digital Video Recorder - No video on first wake up from standby

[Peter5510]

Hi All,
I have this DVR for several years and lately the schedule recording either garbage video or black screen. The audio is OK. After several hours on standby, first wakeup will either have garbage video or black screen. Doing a shutdown and restart after that, everything is OK. I have reformatted the hard disk and the problem still persist.

Can I say that the component of the power board is failing ? If yes, which one should I look at ? Or which one is the main suspect ?

Any repair tips would be much appreciated.

Thanks in advance.

 

[Peter5510]

This is the service manual.
https://www.manualslib.com/manual/692252/Lg-Rh7521w.html
In page 3-29 is the power supply block diagram. 33VT supply to tuner.
In page 3-41 is the psu circuit diagram. Connector P1701 pin5 is 33VT.
C137 is connected to this line. Possible this the problem ?

 

[Relayer]

Can I say that the component of the power board is failing ? If yes, which one should I look at ? Or which one is the main suspect ?

The problem could be on any of the voltage rails. You need to check each one with a voltmeter in the units fault condition to determine which voltage is low or high.
Once you can eliminate other rails from being defective and isolate the right one, its impossible to tell you where to start.
Please let us know what you find.
Regards,
Relayer

 

[Peter5510]

@Relayer,
Thank you very much.
Indeed. I need to check all the voltage supplies to the tuner. Strongly suspect sync voltage.
I found a bandage solution. Just program a short recording about 10 minutes prior to the actual one.
This will ensure the schedule record is OK.
Anyway, I will scrap this unit once they terminate analog broadcast in 2017 in Singapore.