Question about Marshall Televison & Video

Open Question

We have a Marshall VR72P-2C, Dual 7-inch monitor, rack-mounted. The backlights were getting very dim, and we discovered that the inverter boards are bad (the unit was "repaired" by Marshall barely a year ago). Nobody seems to have replacements for the board assemblies, and the LCD modules (AUO model A070FW02) are now listed as obsolete. Are there any newer (LED backlight) versions that would be direct substitutes for these, or, does anyone know of a source for the replacement inverter boards for these?

Posted by Keith Kintner on

Ad

5 Related Answers

Anonymous

  • 44 Answers

SOURCE: Replacing backlight inverter board

Not always but usually the inverter board is part of the display panel, way to much money to bother fixin.

Posted on Jul 03, 2008

Ad

Anonymous

  • 58 Answers

SOURCE: "Upgrade" of Backlight Panel

just replace what failed.
I replace the surface mount FETs on the inverters.

Posted on Dec 06, 2008

Ad

Chi Chu

  • 8457 Answers

SOURCE: How difficult is it to replace backlight inverter on a LCD TV?

Replacing LCD inverter board is very easy.Does not involved in any soldering.It a long board in shape.Just take ur tv aparts,use a Philip screw driver take out 6 Philip screws each board and connections.Do the reverse to install the LCD inverter boards.Tries Websites like Shopjimmy.com,Ebay.com to buy refurbish LCD inverter boards.

Posted on May 01, 2010

budmrtn

Bud Martin

  • 11361 Answers

SOURCE: I got a ELO 1524L LCD touch monitor. The back

You should have 2 wires for 12~15 power going in, which you already indentified, 2 more wires should be for ground return, you can check for them by using Ohm meter between the chassis and probe the wire for less then one Ohm resistance. The other two wires, 1 wire will be for Dimming control (usually 0 = dimmed, 5vdc = full brightness), 1 wire will be for BACKLIGHT ON/OFF (0v= OFF, 4~5VDC = ON) control.
Dose the fuse on the inverter board check out OK? You can use other inveter board as long as the lamp connectors are the same and you just have to match the input signal pin. I have done many.
http://s807.photobucket.com/home/budm/allalbums

http://en.wikipedia.org/wiki/Capacitor_plague
See example of the fuse on the inverter board.


3209760.jpg

Posted on Jul 11, 2010

Martin Murray

  • 1623 Answers

SOURCE: Replaced caps on the psu / inverter board, but

your inverter has gone , if you can see the screen faintly then the inverter isnt illuminating the backlight
it needs replacing

Posted on Mar 03, 2011

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

How do I fix an Acer B273H monitor that has no backlight


More than likely the problem is with the inverter. If you are able to disassemble the monitor, the inverter board should not be difficult to replace. Here is a copy of the service manual - http://www.manualslib.com/manual/249154/Acer-B243hl.html.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/dave_fb2c45146b845cea

Oct 08, 2014 | Acer B273H 27 inch Monitor

Tip

Basic LCD Monitors troubleshooting guides


By Bud Martin
First if you can, try the monitor with other PC first to make sure it is not the PC problem.
Notes: We are dealing with high voltage that can kill you! so if you are not sure what you are doing, please have it fixed by the pro that has proper tools and safety equipment. Try to use GFI outlet and isolation transformer when work around the TV set and DO NOT DEFEAT THE GROUND PIN OF THE OUTLET/POWER CORD.

The monitor will have at least 2 circuits boards, one board will be the logic board where the video cable from PC is attached to, the second board used in most monitors today is the Power supply/backlight inverter board combinations. Some monitors will have separate power supply module and backlight inverter board.
The monitor should be connected to the running PC otherwise it will go into standby mode.
The operations of each board:

1) The Power supply board:
It takes the 120vac 60Hz and converts it to high voltage DC (around 160~170vdc filtered by the 80~150uf 250~450vdc cap) by the bridge rectifiers to be used by the switching power supply circuits that converts this DC voltage into high frequency (around 50~100 KHz) AC for driving the step down transformer. The outputs (usually 2 outputs) of the transformer will be rectified by the diodes to produce the regulated 5vdc for the logic board, and regulated 12~20vdc (12vdc is usually for screen up to 17inch, 16~24vdc for 18~24 inch screen).

The power supply circuits are always on (unless the monitor uses the power switch that actually disconnects the power from the outlet which is rarely used these days) which means that it is running 24/7 using the monitor or not, any spikes and surge will be fed into the monitor power supply.

Common problems:
Blown fuses, bad caps (leaking/bulging tops or bottom seals, please note that bad cap may look normal but it can have high ESR (Equivalent Series Resistance). The DC filter cap should be low ESR type for using in the switching power supply; general purpose electrolytic types will not last very long in switching power supply circuits. Poor solder joints, over heated components.

Testing:
Plug the monitor in but do not activate the power switch so the backlight inverter circuits will be off. Check the 5vdc and the 12~24vdc to make sure they are OK. They should be tested with the load, you can use 6V 1A (6watts) lamp for the 5vdc, and car lamps such as 1157 (12v 8watts lo/26watts high) turn signal brake lamp using high filament connection for testing the 12~18vdc (or use two 1157 in series for 19~24vdc) for the backlight inverter circuits.
If the power supplies are working, the output voltages should be steady at the rated voltages. The power supply will go into shut down if it detects too much current draw due to false in the power supply or short circuits in the backlight inverter or in the logic board.

2) The backlight inverter circuits:
It takes the 12~24vdc and converts it to high frequency AC to drive the inverter transformers CCFL (Cold Cathode Fluorescent Lamp) assemblies. The transformers will drive the CCFL by applying the start up voltage (around 1500~2000v), when the CCFL start conducting, the voltage will drop down to about 500~800v.
The inverter has detection circuits to detect open circuit if the lamp is not attached or does not fire up after the start up voltage is applied, it will go into shut down. It will also shut down if the lamps draw too much current due to ages (when lamp gets old it will draw more current).
The inverter gets two signals from the logic board, one is the backlight ON/OFF signal, the other one is the Dimming signal for the lamps.
Common problems:
Bad filter caps, resonant caps (in the inverter output circuits), blown transistors/IC, shorted or open transformer winding.
Testing:
You should have spare lamps for testing the inverter circuits.

3) Logic board:
The logic board get the signals from the VGA (ANALOG) or DVI (DIGITAL) and processes them and feed them to the LCD panel T-CON (Timing Controller) board on the back of the LCD panel.
It also sends out two signals (backlight ON/OFF and Dimming) to the inverter circuits when the monitor is on and getting the signals from the PC.
If the logic board does not get the signal from the PC, it will put monitor into standby mode.
The 5vdc feeding it is converted to 3.3v, 1.8vdc by the switching buck converters to run the processor.
The logic board also sends the 5vd or 12vdc power for the T-CON board, if the voltage is not there, you will see white/grey glowing screen only.
Not much repair you can do on the logic board unless you have the full service manual and surface mount repair station.

4) CCFL and Inverter circuits testing:
If you don not have the inverter and lamp tester boxes you may be able to do a simple test by using these steps:
If the screen flashes on for a second, you can disconnect all the lamp connectors and connect it into one of the transformer output connector and see if you will see the flash on the screen, if you do, then try it with another transformer output connector to see if it also get the flash on the screen.
Repeat the procedure with other 3 lamps. If all the lamps do flash on for seconds then more likely the lamps are OK. If lamp only flash on one of the transformer output then you will know that the problem in that transformer inverter circuits.
If none of the lamps flash at all then the problem is in the inverter circuits, power supply, or not getting the on signal from the logic board.

Bad caps
http://i.fixya.nethttp://i.fixya.nete17e9cc.jpg

Power supply/inverter board (L), Logic bd. (R)
http://i.fixya.nethttp://i.fixya.netbc19983.jpg'

Dead T-CON bd, blown fuse. Get glowing screen only.
http://i.fixya.nethttp://i.fixya.net4fbd9e1.jpg

T-CON board's fuse F101
http://i.fixya.nethttp://i.fixya.net8506e44.jpg

Inverter board surface mounted fuses, F1 and F2

http://i.fixya.nethttp://i.fixya.net1bf6596.jpg
Bad lamps (Blackened ends, burnt /poor soldering)

http://i.fixya.nethttp://i.fixya.net5c8952e.jpg

http://i.fixya.nethttp://i.fixya.net4e5e9a1.jpg

Bad LCD panel (solid vertical lines)

http://i.fixya.nethttp://i.fixya.netffe90fe.jpg

Bad LCD panel due to bad T-CON board
http://i.fixya.nethttp://i.fixya.netef48b18.jpg
Failed TV and Monitors:
http://s807.photobucket.com/albums/yy352/budm
http://en.wikipedia.org/wiki/Capacitor_plague
Make your own test lamps: http://www.badcaps.net/forum/showthread.php?t=19987

on Sep 25, 2010 | Computers & Internet

1 Answer

3 year old LG model L196WTQ Flatron screen has gone blank (black)


It's probably a backlight or backlight inverter issue if the problem occurs on all sources and the onscreen menus. (The backlight itself usually fades or makes the on-screen image change to pink/red.) With a bad backlight, you'll usually see a very dim image if you look at the monitor from an inch from the screen. Block the room light from overwhelming this image (sometimes a carefully positioned flashlight will help you see something). If the inverter or video board is bad, you will see nothing. For an out-of-warranty monitor, open up the back of the monitor and remove the shielding. Look for any scorch marks or bulging or damaged capacitors. (Sometimes other parts will fail on this part but these can be spotted easily. Capacitors look like cylinders on a tripod.) The scorch mark and smoke may indicate a resistor or zener diode that had been used as a fuse and is now gone.

If you borrow (or have a) high-end multimeter (able to measure high frequencies - 50 kHz) or an oscilloscope, hold the multimeter probes a fraction of an inch apart about an inch above the inverter board and power up the monitor. If you see a 1 or an actual value, you have a good inverter. If you see a reading near 0, the board is bad or the multimeter can't resolve the frequency.

In either case, you can buy a replacement inverter for $50-150 and just do a simple swap. Disconnect all of the wires (connections are similar to molex and ribbon cables in a computer) and remove board (a few screws usually). Connect the cables to the new inverter. (If you google backlight inverter replacement, you'll find videos and text descriptions.) Note the part number on the board, including the Rev number, and order the exact one (shopjimmy.com or lcdparts.net are good starting points). Universal inverters do exist but can result in reversed controls (up to lower the brightness). Replacing individual parts on the board is cheaper but more prone to not tracking down all of the bad parts.

If the inverter is good, then it's probably backlights themselves (several in most monitors). These are sandwiched on the perimeter of the monitor (usually under some tape that holds the lamp, reflector and other parts together. You need to order by length and width and get ones for your monitor size. Separate the panel from the bezel. Remove the tape, and separate the reflector (make a note of how things are put together) then you have to Dremel (or use another rotary tool) to remove the plastic to get the backlight out. (They are often molded into the frame.) Then put in the new backlight and reassemble everything. See http://www.lcdparts.net/howto/default.aspx for more information but for an overview: http://www.inventgeek.com/Projects/BacklightFix/overview.aspx. Then push the new backlights into place, reconnect the wires and close up the sandwich of tape and other parts around the screen. Then replace it in the bezel.

With a good spare backlight, you can test an inverter for condition (plug together and turn on the monitor while the box is open). Similarly a good inverter can test the backlight.

I hope this helps.

Cindy Wells

Feb 22, 2011 | Computers & Internet

1 Answer

I have a dual LCD Marshall Electronics V-R72P-2C. All LEDs are lit, with no displays. Any ideas of problem, or how I could troubleshoot?


I would first try the fuses. There is a 3 amp, surface mount fuse on each board. [F1] Even if the LED's are on, the fuse is probably bad.

Jan 29, 2011 | Marshall Televison & Video

1 Answer

Monitor has gone dark. Have checked connections and cables. Also attempted a system reboot and power down. No luck


Do you have the power light lit (standby or on)? If that light is not on, then it is probably the power supply.

Otherwise it is the board that translates the signal to the screen, the backlight or the inverter. It's a backlight or backlight inverter issue. (The backlight itself usually fades or makes the on-screen image change to pink/red.) With a bad backlight, you'll usually see a very dim image if you look at the monitor from an inch from the screen. Block the room light from overwhelming this image (sometimes a carefully positioned flashlight will help you see something). If the inverter or video board is bad, you will see nothing. For an out-of-warranty monitor, open up the back of the monitor and remove the shielding. Look for any scorch marks or bulging or damaged capacitors. (Sometimes other parts will fail on this part but these can be spotted easily. Capacitors look like cylinders on a tripod.) The scorch mark and smoke may indicate a resistor or zener diode that had been used as a fuse and is now gone.

If you borrow (or have a) high-end multimeter (able to measure high frequencies - 50 kHz) or an oscilloscope, hold the multimeter probes a fraction of an inch apart about an inch above the inverter board and power up the monitor. If you see a 1 or an actual value, you have a good inverter. If you see a reading near 0, the board is bad or the multimeter can't resolve the frequency.

In either case, you can buy a replacement inverter for $50-150 and just do a simple swap. Disconnect all of the wires (connections are similar to molex and ribbon cables in a computer) and remove board (a few screws usually). Connect the cables to the new inverter. (If you google backlight inverter replacement, you'll find videos and text descriptions.) Note the part number on the board, including the Rev number, and order the exact one (shopjimmy.com or lcdparts.net are good starting points). Universal inverters do exist but can result in reversed controls (up to lower the brightness). Replacing individual parts on the board is cheaper but more prone to not tracking down all of the bad parts.

If the inverter is good, then it's probably backlights themselves (several in most larger monitors). These are sandwiched on the perimeter of the monitor (usually under some tape that holds the lamp, reflector and other parts together. You need to order by length and width and get ones for your monitor size. Separate the panel from the bezel. Remove the tape, and separate the reflector (make a note of how things are put together) then you have to Dremel (or use another rotary tool) to remove the plastic to get the backlight out. (They are often molded into the frame.) Then put in the new backlight and reassemble everything. (http://www.lcdparts.net/howto/default.aspx) but for an overview: http://www.inventgeek.com/Projects/BacklightFix/overview.aspx Then push the new backlights into place, reconnect the wires and close up the sandwich of tape and other parts around the screen. Then replace it in the bezel.

With a good spare backlight, you can test an inverter for condition (plug together and turn on the tv while the box is open). Similarly a good inverter can test the backlight.

I hope this helps.

Cindy Wells
(inverters usually fail before CFL backlights or the video board)

Oct 15, 2010 | Westinghouse 19" Widescreen Flat Panel LCD...

1 Answer

Screen light goes on then dims so low you cannot read


Try attaching an external monitor to the laptop & see if you could get any display on it. If this is successful, then you might have either a faulty LCD cable or screen inverter board.
The LCD cable transfers data signal from the motherboard & video card to the LCD screen. It also supplies high voltage DC power to the screen inverter board. The screen inverter board works as a power supply for the backlight lamp mounted inside the LCD screen. It converts low voltage DC power to high voltage AC power needed for the backlight lamp.

Sep 06, 2010 | Compaq Presario CQ60-220US PC Laptop

1 Answer

Very dim monitor


Try attaching an external monitor to the laptop & see if you could get any display on it. If this is successful, then you might have either a faulty LCD cable or screen inverter board.
The LCD cable transfers data signal from the motherboard & video card to the LCD screen. It also supplies high voltage DC power to the screen inverter board. The screen inverter board works as a power supply for the backlight lamp mounted inside the LCD screen. It converts low voltage DC power to high voltage AC power needed for the backlight lamp

Sep 04, 2010 | Computers & Internet

1 Answer

I have a CTX s761 lcd monitor. The image on the screen will be clear for about a minute, then it gets very dark and can only see a ghost of the image. Power off and back on and it does the same thing...


It's a backlight issue. (The backlight itself usually fades or makes the on-screen image change to pink/red.) With a bad backlight, you'll usually see a very dim image if you look at the monitor from an inch from the screen. Block the room light from overwhelming this image (sometimes a carefully positioned flashlight will help you see something).

The backlights are sandwiched on the perimeter of the monitor (usually under some tape that holds the lamp, reflector and other parts together. You need to order by length and width and get ones for your monitor size. Remove the tape, and separate the reflector (make a note of how things are put together) then you have to Dremel (or use another rotary tool) to remove the plastic to get the backlight out. (They are often molded into the frame.) Then put in the new backlight and reassemble everything. (http://www.lcdparts.net/howto/default.aspx) but for an overview: http://www.inventgeek.com/Projects/BacklightFix/overview.aspx . lcdparts.net sells backlights for some laptops and monitors. There are other sources.

The inverter board or the video board can also fail but you usually won't see any image when those fail. For an out of warranty monitor, open up the back of the unit and remove the shielding. Then look for any scorch marks or bulging or damaged capacitors. (Sometimes other parts will fail on this part but these can be spotted easily. Capacitors look like cylinders on a tripod.)

If you borrow (or have a) high-end multimeter (able to measure high frequencies - 50 kHz) or an oscilloscope, hold the multimeter probes a fraction of an inch apart about an inch above the board and power up the monitor. If you see a 1 or an actual value, you have a good inverter. If you see a reading near 0, the board is bad or the multimeter can't resolve the frequency.

In either case, you can buy a replacement inverter for $50-150 and just do a simple swap. Disconnect all of the wires (connections are similar to molex and ribbon cables in a computer) and remove board (a few screws usually). Connect the cables to the new inverter. (If you google backlight inverter replacement, you'll find videos and text descriptions.) Note the part number on the board, including the Rev number, and order the exact one (shopjimmy.com or lcdparts.net are good starting points). Universal inverters do exist but can result in reversed controls (up to lower the brightness). Replacing individual parts on the board is cheaper but more prone to not tracking down all of the bad parts.

With a good spare backlight, you can test an inverter for condition (plug together and turn on the monitor while the box is open). Similarly a good inverter can test the backlight. If the inverter or video board is bad, you will see nothing

I hope this helps.

Cindy Wells

Jul 27, 2010 | Computers & Internet

1 Answer

LCD model viewSonic vx2235wm, screen is dark, no visual display. However, blue light at the bottowm is on.


It's a backlight or backlight inverter issue. (The backlight itself usually fades or makes the on-screen image change to pink/red.) For an out-of-warranty monitor, open up the back of the monitor and remove the shielding. Look for any scorch marks or bulging or damaged capacitors. (Sometimes other parts will fail on this part but these can be spotted easily. Capacitors look like cylinders on a tripod.)

If you borrow (or have a) high-end multimeter (able to measure high frequencies - 50 kHz) or an oscilloscope, hold the multimeter probes a fraction of an inch apart about an inch above the board and power up the monitor. If you see a 1 or an actual value, you have a good inverter. If you see a reading near 0, the board is bad or the multimeter can't resolve the frequency.

In either case, you can buy a replacement inverter for $50-150 and just do a simple swap. Disconnect all of the wires (connections are similar to molex and ribbon cables in a computer) and remove board (a few screws usually). Connect the cables to the new inverter. (If you google backlight inverter replacement, you'll find videos and text descriptions.) Note the part number on the board, including the Rev number, and order the exact one (shopjimmy.com or lcdparts.net are good starting points). Universal inverters do exist but can result in reversed controls (up to lower the brightness). Replacing individual parts on the board is cheaper but more prone to not tracking down all of the bad parts.

If the inverter is good, then it's probably backlights themselves (several in most TVs). These are sandwiched on the perimeter of the monitor (usually under some tape that holds the lamp, reflector and other parts together. You need to order by length and width and get ones for your monitor size. Remove the tape, and separate the reflector (make a note of how things are put together) then you have to Dremel (or use another rotary tool) to remove the plastic to get the backlight out. (They are often molded into the frame.) Then put in the new backlight and reassemble everything. (http://www.lcdparts.net/howto/default.aspx) but for an overview: http://www.inventgeek.com/Projects/BacklightFix/overview.aspx

With a good spare backlight, you can test an inverter for condition (plug together and turn on the tv while the box is open). Similarly a good inverter can test the backlight. With a bad backlight, you'll usually see a very dim image if you look at the monitor from an inch from the screen. Block the room light from overwhelming this image (sometimes a carefully positioned flashlight will help you see something). If the inverter or video board is bad, you will see nothing

I hope this helps.

Cindy Wells

Jul 27, 2010 | ViewSonic VX2235wm LCD Monitor

1 Answer

I got a ELO 1524L LCD touch monitor. The back


You should have 2 wires for 12~15 power going in, which you already indentified, 2 more wires should be for ground return, you can check for them by using Ohm meter between the chassis and probe the wire for less then one Ohm resistance. The other two wires, 1 wire will be for Dimming control (usually 0 = dimmed, 5vdc = full brightness), 1 wire will be for BACKLIGHT ON/OFF (0v= OFF, 4~5VDC = ON) control.
Dose the fuse on the inverter board check out OK? You can use other inveter board as long as the lamp connectors are the same and you just have to match the input signal pin. I have done many.
http://s807.photobucket.com/home/budm/allalbums

http://en.wikipedia.org/wiki/Capacitor_plague
See example of the fuse on the inverter board.


3209760.jpg

Jul 11, 2010 | Elo 15" Touch Monitor

Not finding what you are looking for?
Televison & Video Logo

Related Topics:

58 people viewed this question

Ask a Question

Usually answered in minutes!

Top Marshall Televison & Video Experts

The Knight
The Knight

Level 3 Expert

76352 Answers

Cindy Wells

Level 3 Expert

6099 Answers

Marvin
Marvin

Level 3 Expert

85239 Answers

Are you a Marshall Televison and Video Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...