Question about Sony SDM-HS73P 17" LCD Monitor

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Monitor won't turn on, no led.

My monitor won't turn on. I am an electronic technician myself, so I started checking. I have both 5 volts and 12 volts from the inverter board that feeds the video board.These voltages are marked on the inverter board. The On/Off line is measuring 0.15 volts, and the Dimming line is 2.6 volts. I also measured 3.3 volts on each side of the power switch, and pushing it makes no difference. I checked the switch itself, and it is good. This tells me that a voltage regulator is working. If the control for turning on this monitor must come from the video board,or must the ON/off line be a voltage developed from the inverter board sent to the video board? If so, this may suggest a problem such as a defective opto-isolator on the inverter board. I cannot find good service literature on this.

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Re: Monitor won't turn on, no led.

If you have a monitor which has an external power that power supply can be substituted for another one by soldering the positive and negative cords to the back of the circuit board, but I found out that I have to stick something into the power jack to push down a contact thing so that it does not connect with another part of the jack that shorts the connection. I found this out on my own just now. Free lcd monitor, didn't work because it had no power supply and the power button was busted. I am going to school to be a computer engineer, sorry if I don't have the right terminology.

Posted on Aug 01, 2010

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Re: Monitor won't turn on, no led.

Hi guys, just been reading your posts on the symptoms regarding this montor. I have a very similar problem whereby, no power light is displayed and monitor is totally dead. Any idea where i can get a replacement graphics card? My chip states LHS93K v1.0 THANKS ALL

Posted on Jun 01, 2008

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Re: Monitor won't turn on, no led.

I am having the same problem with one of these monitors, however, i'm in a unique situation. I have one that works and one that doesn't.

I narrowed it down to being the power controller / video signal processing circuit board in this LCD. When I swapped this part alone (after checking the power supply very carefully), the dead monitor came to life. The model number of this part (Manufactured by LG, NOT SONY) is LHS73K. The Version 1.2 is the dead one, the version 1.3 is the good one. Even though the plastic connectors are slightly different, the pinouts are the same and the pins do line up, so I swapped the controllers, and the dead monitor came to life. I notice the dead controller card's GENESIS IC gets slightly warmer than it does with the working one.

I took some high resolution pictures of the 2 cards, and highlighted (light yellow boxes) some differences....

(i'm hosting the pictures on my own file server because they are 1.5mb each, and fixya puts a limit on the file size you can attach a picture with)

Working v1.3 Image: <url></url>
Dead v1.2 Image: <url></url>

I am going to do some more work and see if I can bypass the soft-switch with a hard-switch to turn the power supply on in the dead monitor, if that works, i'll update the post and let everyone know what and how I did it.

Posted on Nov 27, 2007

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Re: Monitor won't turn on, no led.

If the LCD has an internal power supply, then the inverter circuit should be on the board as the power supply. If the power supply is external, then the inverter circuit will have it own board.

What is the output of the Inverter circuit? It should have 12VDC going in, but around 50VAC going to the CCFL bulbs.

The "no led" should be a sign. Your getting voltage, but what about current? It still can be the power supply. All LCD monitors should have a "soft switch", or software driven switch to turn the CCFL lamps on and off.

It is hard to find literature on LCD repair, experience is the best teacher on this subject. This might take several emails or postings to help find the answer.

LCD monitors are a computer. You can break them into several parts, Power, I/O, and processing. Power is the easiest to trouble-shoot and repair. Processing is the hardest.

I fixed one LCD monitor by re-seating the software EEPROM. The process could not do its job if it can not read the software EEPROM.

If one of your IC's is shorted, you can always tell using a can of air. Get one of those cans of air and tip it upside down and spray the entire board until it all turns white. Now apply power to the system. If an IC is shorted, it generates more heat than anything else. It will be the first to loose the white condensation. Don't worry this is safe, done it several times.

Posted on Nov 16, 2007

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