xxx13 Video Interference Elimination & Blinking Green Light Fix.

 

Author:  Jonathan Rodda  03/02/07

 

Acknowledgements

 

This fix was not discovered by me.   A great debt of gratitude is owed to Servicetech, Phantom319, Craigr, Robert Vermazen and all those who invested their time in solving these two problems. 

 

Background

 

Many xxx13 users have experienced two common problems.  The first is video interference that appears in either 1080i material and/or the On Screen Display (OSD) window in all scan rates.  It consists of faint horizontal lines spaced about 5mm apart.  These lines scroll vertically, slow down then reverse direction.  The lines fade away and this cycle repeats. 

 

The other common problem is a constantly blinking green power light during which the TV cannot be turned on.   Sometimes the TV will shut itself off and the power light will continue to blink. 

 

Both of these problems are caused by failing capacitors on the DM module.  If either of these symptoms is present, repair the DM AS SOON AS POSSIBLE.   Once the capacitors fail, they can cause catastrophic damage to the rest of the DM module and this board costs about $1000 to replace.

 

The DM module is a micro PC that controls many functions from processing digital audio and HDTV to generating the OSD graphics.   When the TV is connected to a power source, the front panel green light will blink for about a minute indicating that the DM is booting up. 

 

As a side note, some of the shutdown problems were fixed with a firmware update.  If you have this problem, first check that you have version 003.03 of the firmware.  With the remote enter MENU 0-3-7-0 and the Option menu will appear displaying the firmware version.  Hit the MENU button again to exit.  You can obtain a firmware update on a compact flash card from Mitsubishi by calling their customer support line.

 

Affected Models

 

The xxx13 series, based on the V23 chassis, have experienced problems with their DM module and there are two versions of this board.  The WS-55813, WS-65713, WS-65813 and WS-73713 all share the same DM module: 934C067002 ASSY-PWB-DM and the remaining xxx13 models use: 934C067001 ASSY-PWB-DM.

 

Solution

 

The fix for both the video interference and blinking green light is to replace all four electrolytic capacitors on the DM module.  The original capacitors are 1000uF 16V 105C radial lead, and measure 10mm in diameter and 16mm tall.  Space it tight; the shield offers little clearance and the capacitors are mounted close together.  Replacement capacitors should be as close to 10x16mm as possible. 

 

The factory installed capacitors fail due to excessive heating and should be replaced with high endurance, long life capacitors.  Robert Vermazen has done an analysis of why the factory capacitors fail and you can see the details in Craigrís post #828622 here.  It is also a good idea to add a fan to the DM module to provide additional cooling.

 

WARNING!

The following instructions should be followed by a qualified service person only.  Opening  the TV will expose you very high voltages so therefore use caution.  Doing the wrong thing could very easily render your TV unusable.  This is for information purposes only and neither I nor The Home Theater SPoT can be held responsible for any damage or injury that may result from attempting this repair.

 

Materials

 

For this repair you will need a Phillips screwdriver, low wattage soldering iron, a desoldering tool, and four electrolytic capacitors.  For the optional fan replacement you need a PC cooling fan, zip ties, foam tape (or  weather stripping) and a 12v AC to DC power adapter.

 

Craigr recommends Panasonic 10,000 hour high temp capacitors (part number: P13119-ND ) and they can be purchased from http://www.digikey.com.  I also recommend the Radio Shack desoldering tool cat# 64-2060.  Itís only $10 and will make quick work of removing the old capacitors without damaging the board.

 

Procedure

 

This is a fairly simple repair for those with a little soldering experience.  Start by unplugging the TV and remove the rear panel.  If you are going to install a fan, position it on the right side of the shield (as seen from the rear) and mark its outline with a pencil.  It is easiest to install the fan with the shield removed from the TV, but by marking its mounting position first, you will avoid placing the fan on a part of the shield that has an obstruction.  The DM guide partly covers the capacitors that need cooling and the metal tray under the CRTs also restricts fan placement.

 

 

Unplug the coax and digital audio cable (if present) from the DM rear panel and remove the plastic panelís mounting screws and panel.  Pull out and set aside the PWB-DEMOD board.  It is a small vertical card just to the left of the DM and has a broad copper grounding spring.  This step is necessary to access one of the DM shield mounting screws.  See picture below.

 

 

 

The DM and the shield are removed vertically so in order for there to be enough clearance, the chassis needs to be pulled toward the rear of the TV.  All the electronics are mounted on a tray that can slide back like a drawer to make servicing easier.  Unplug the USB and Firewire cables from the top of the DM.   Unplug the cable that runs from the front input jacks to the connector on top of the terminal board and unscrew the grounding strap from the top of the doubler shield.

 

 

Remove the board slide.  It is a narrow fiber board that stretches the width of the TV above the rear of the chassis and shields the light box from scattered light.  It is held in place by a long black screw on either side of the TV.  Use caution as the board may fall when the screws are removed.

 

Undo the wire ties on the cables going to the front of the TV.  You will need slack in these wires as you slide the chassis out.  You will also need to unplug some of the connectors on the shorter wires.   Remove the screw (a) on the edge of the chassis and screws (b) on the xx813.  See diagram below. 

 

 

Release the chassis lock tab on either side of the chassis.  The tray may be a bit hard to slide, so alternately tug on the left and right edges to rock the tray rearward.  Go slowly in case youíve missed freeing a wire bundle.  Pay attention to the large red anode wires and other cables on the right hand side as they are clipped to the frame of the TV.  Pull the chassis back until the DM shield will clear any obstructions above.

 

Note:  Do not use a power screwdriver on the following screws as it is very easy to strip the threads.   Remove the screws holding the DM shield.  There are two on top of the shield, two in the rear base and one in the middle of the base on either side of the shield (see photo above).  The DM shield can be snug and hard to pull up. Gently rock the shield front and back while applying upward force. You may want to hold down the board below (DTV-TUNER) to avoid disturbing the ribbon connectors to the signal board. The DM itself also comes out straight up, but it is not nearly as tight.  Handle the DM by the edges to avoid static damage.

 

If you hold the DM with the components facing you and the external connectors on the left, you can find the capacitors in question in a cluster on the top right corner of the board.

 

 

 

Here is what a typical capacitor failure may look like:

 

 

The top of the capacitors shown above may only have a slight bulge, but they have indeed failed.  After removal, these four capacitors measured 209uF, 203uF, 29uF and 7uF!

 

Desolder and replace all of the capacitors at the same time.  When inserting the new capacitors, pay close attention to the polarity.  The rear of the board has the positive terminal labeled and the longest lead is positive.  The capacitor body has the negative terminal marked by dashes running down one side.  All the capacitors have the same orientation: 

 

 

 

Insert all four capacitors as close to the board as possible.  The Panasonic capacitors are 4mm higher than the stock capacitors and there is very little extra room inside the shield.

 

 

 

If you are going to install a cooling fan do so now.  Stick some foam tape or adhesive weather stripping to each corner of the fan.  This will minimize fan vibration noise and provide the fan with some clearance from the shield.  The shield has a thin ridge that runs diagonally and prevents the fan from sitting flush, but the foam tape will allow the fan to straddle the ridge.

 

 

Place the fan on the pencil lines you drew earlier and secure two diagonal corners of the fan with small zip ties through holes in the shield.  The zip ties are flat and their low profile will allow the shield to slide over the DM board without getting caught.  Pictured above is an 80mm 12v 340mA PC fan which is powered by an external 12v supply.  You can run your fan from a 6v power supply to minimize noise, but test it first as not all PC fans will spin up with just 6v.

 

Installation

 

Installation is the reverse of removal.  The DM will slide down onto the four connectors at its base and there is a plastic vertical guide to ensure proper alignment of the board.  Be careful not to bend the copper grounding springs that touch the connector end (rear) of the DM as it slides back into place.  Carefully slide the DM shield back over the DM board and be careful not to snag the taller capacitors.  Install the 6 screws that secure the DM in place.  (Note that the two screws on the top of the DM shield are different from the other four).  Plug the PWB-DEMOD card back in and ensure that its copper ground spring is touching the left edge of the DM shield.

 

Slowly slide the chassis back into the TV and be careful not to pinch any wires running to the front of the TV.  The chassis should click as the release tabs lock into place.  Secure the chassis with the long black screws.  Reconnect all the wires you had removed and secure the excess slack back into the wire ties.  Plug the USB and Firewire connectors back on the top of the DM and plug the cable from the front inputs back onto the top of the terminal board.  Screw the grounding strap to the top of the doubler shield.  Do not over tighten it as it is easy to break the threaded mounting plate on the shield.  Install the DM rear cover and screws.  Reconnect the coax antenna and digital audio cable back into the DM (if applicable).

 

Lastly, put the board slide back and remember that it could fall unless properly screwed in place.  Double check all the connectors on the boards to be sure you havenít missed reconnecting anything.  Install the rear cover of the TV and route the optional fanís power cable over the top of the rear cover to avoid pinching the cable.

 

Plug the TV back in and the front light should blink for about a minute as the DM boots.  When the light has turned off, power up the TV and verify operation.  If all goes well, your TV should boot in about one minute and there should be no more interference in the picture or OSD.

 

Have fun, and be careful!