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Coby TFTV4028 LCD TV won't turn on. Blue light is on, but pressing power button doesn't do anything.

I am trying to troubleshoot this as to whether it is the main board or the power supply. There is 110V AC at the input to the power supply board VP270UG01-GP ver. 1.0, and the fuse tests ok, but the outputs never have the stated voltage 5V, 24V. Pin 9 on CN3 is labeled as PSON on the board, which I guess is a signal telling the power supply to wake up, but this never changes from 0V when the power button is pressed. Is it more likely to be the main board 002-FV40-2810-00R ver 1.0 not sending the required signal that is the problem? Is there a way to verify this before I order and replace the wrong part?

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  • Coby Master
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Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Pull up older posts. In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.
Before going further; try a hard reset first. If it does not help you, replace the main digital board. There are two methods to reset TVs. The first is simple to do; a Hard Reset. The other is somewhat skilled; is a Factory Reset (System Reset). To make it a hard reset, just unplug the TV from AC mains wall socket, and re-plug it back after 15 minutes or so. If you do this by overnight is better. This procedure will make it a hard reset. If you want to make it a system reset [Factory Reset]; you have to enter its service mode option, and select the factory reset option. If you wish to get some details; visit the site linked here.

Posted on Jan 03, 2017


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Posted on Jan 02, 2017

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SOURCE: I have a NS-LCD37-09 tv. No picture or backlight

Your main board is faulty. I've done several of these but haven't been able to figure out which component is actually bad these yet. I've simply had to replace the board itself, and it fixes it every time. One thing you can do to get your backlights to come on (and so you know I'm not Jive'n you) Is unplug the three wire bundle that spans from power supply to main board. This will usually make the backlights fire up. I even had one that after I left it that way for a minute (with the backlight on) it suddenly started working again! But this was short lived. :-(
One time I even tried recapping the entire main to see it that would fix it. It did not. I think it might be something to do with the small chip labeled SL37HA37. It's a 16 legged bastard near the 3-wire plug I told you to pull. It's that or possibly the bigger IC near it that has a heat sink on it. The ball grid array solder joints may be faulty. Just guesses, if any smart guys out there figure this one out, be sure to tell the rest of us please!
Thanks, Chris Boise LCD

Posted on Apr 23, 2010

  • 1 Answer

SOURCE: ILO LCD, Power supply issue, MLT169B. 24v output is dead.

I want to know R3 value

Posted on Dec 27, 2010

  • 11361 Answers

SOURCE: Sharp Aquos LC-42DH77E 42" LCD TV TV appears to

The PNL-POW (LCD panel Power) and the PS-ON will be 0V until the main board send out the signal to turn them on, it is working.
Do you get backlights?
Did you check the fuses on the Inverter board? You power supply is working.
This service manual may match your chassis:

Basic LCD monitor and TV troubleshooting guide:
Failed TV and Monitors pictures:
Learn about bad caps:
Capacitors kit: he can make you a set of caps.
Or, just make sure to use caps with low ESR, 105c, high ripple current and long life rating such as PANASONIC FM or FC series.

Posted on Jun 01, 2011

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that is main board issue..

Posted on Jun 15, 2012

  • 1182 Answers

SOURCE: Power supply board troubleshooting - p50x01au

If you have a service manual, please match the voltages as per that and problems might be in areas where these do not match. But read on what condition these voltages are to be checked, this is usually written in a service manual, i.e, without any signal or feeding some signal etc.

Posted on Aug 06, 2012

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