Take Apart Tuesday No. 1: Samsung Flat Screen Monitor

On Monday one of our members brought in some spare flat-screen monitors. They had gotten that droopy syndrome pivoting monitors sometimes come down with.

Most of them work just fine for our purposes, but one of them popped and didn’t light up when it was tested that night.

The next day, with the sun shining, no internet, and a cable guy on the roof, ripping it to pieces seemed the only thing to do. Take it Apart Tuesday was born.

Hardware Hacking Basics

If you are going to start hacking things to pieces here are some good tools have:

• Assorted screw drivers (the computer sets are nice, but really just a regular flat head and basic Phillips is enough to start. They’re all we used for this)
• A knife (just in case)
• Blue masking tape (to tape down screws)
• A sharpie (to label the blue tape, if needed)
• A camera (so you know where things went)
• Small led flash light (makes part numbers easier to read)

Once you want to start seeing what does or does not work, rather than just an anatomy lesson add:

• A fused multimeter
• Internet access to look up part numbers

Super Basic safety:

• Be unplugged. (Not having things plugged into the wall is obvious, but remove internal batteries, too. )
• Check that all switches are in the off position.
• DO NOT touch large capacitors.
• Wear safety glasses if you are prying anything apart. (TIP: if you are near sighted, you’ll want to be wearing your glasses anyway to make reading part numbers easier)
• Wearing rubber soled shoes never hurts.

If you are going to take on a more radical parts harvesting than we’re doing here , i.e. desoldering individual items to use in a different circuit, be really really careful about fumes.  Solder has a number of chemicals that are incredibly harmful to breathe, so, bare minimum, have a fan and a window open, please.

Here is an Instructable on just that:
http://www.instructables.com/id/Recycle-old-PCB-components/

Our Victim: The Samsung LCD Monitor Model 244T S

The easiest part to salvage is the AC -> DC power converter, but the basic parts overview for the whole system is:

• 8 Circuit Boards
  1. PCB 1 The buttons for the front, connected to the video board [Flickr]
  2. PCB 2 The USB hub: BN41-00663A (SMSC USB2504-JT) [Flickr]
  3. PCB 3 Power converter: PSLF101401A, connected to the Board 4 in two places [Flickr]
  4. PCB 4 Video In / Processing: BN41-00659B [Flickr]
  5. PCB 5 LCD power supply: LCD Inverter board GH151A [Flickr]
  6. PCB 6 Logic Board: 240WUC4LV0.5 [Flickr]
  7. PCB 7 240M1S6LV0.4: No Google results but was connected to Logic board/long edge of LCD and has Rail-to-Rail Input-Output Op Amps (5420CRZ) [Flickr]
  8. PCB 8 240M1L01G_2LV0.1: Again no Google results, connected to short edge of LCD from logic board [Flickr]
• LCD
• Back Light & Filters
• Various pieces for the housing

There is now a section on the WIKI dedicated to Take Apart Tuesday so as people play with the different parts we can all keep learning. If you want to help identifying parts and aren’t sure where to start here are some good sites to start with:

To know what you’re looking at:
http://www.uchobby.com/index.php/2007/07/15/identifying-electronic-components/

To figure out what an IC is you can stick the part number into Google or find some help at the following two sites:
http://www.chipdocs.com/
http://www.educypedia.be/electronics/datacomponent.htm

We didn’t really think we’d be documenting this when we started so there are gaps and stuff, but here is the general overview.

http://www.flickr.com/photos/carlynorama/sets/72157623164028170/detail/

(we don’t have the flickr plugin yet… coming)

Harvesting the Power Supply

What popped during testing was probably one of the tubes in the back light.  If we were um, actually trying to fix it, we’d go through part by part seeing what broke. The first thing to check would be the power supply.

The power supply converts AC voltage into usable DC voltage.  Here are the steps we took to see if it was working. Tom took the lead on this part.

Notice in the images of the back area that the “HOT” or high voltage/AC area is marked off in black. This is the part that can hurt you so be careful working with components in this area.

Step 1: Unplugged it, made sure the switch is was off.

Step 2: Checked for continuity across the fuse (most likely thing to be broken)

Step 3: Checked the main capacitor for charge build up

These large capacitors can hold on to a charge for a long time and zap you.

Step 4: Plugged it in, turned it on, tested DC outputs

The low DC voltage pads read true, but no love on the 24 V connection, so to see if the problem was somewhere in the AC -> DC conversion we…

Step 5: Checked across the Bridge Rectifier

Everything looked good, in excess of 100 V there! HOT!

Step 6: Plugged it back into PCB 4 to check if there was something extra going on.

If you noticed, one of the pads in the low voltage part is labeled on/off.  We plugged that connector back into PCB 4 and let the power flow into that board, too. We got back a 3.3 V signal on the On/Off pad and then found that the 24 V pads lit up, too.  IC502 on PCB 4 is a 3.3 V regulator. A little more checking could find out if PCB 4 is just passing voltage straight back or if there is a system check happening in some other part of the circuit which gives the all clear.

The End: So now at the very least we have a 6V and multiple 24 V AC to DC power supply that we can use in other projects.Yay!