Emerson lc407em1 Turns on screen only flashes, then off

[proaudiosoft]

Hi, I am new to these forums, I have repaired several tv's , Just wanted to see if I could get some help on this one. The powerboard (and other boards) have no visible bad caps. Power seems ok at any marked voltage points on the power board. The inverter visibly looks ok too. When power is pressed the green light comes on, flashes 15 times, then back to red. I was thinking the problem is possibly the inverted since the screen just flashes very briefly then off like a second later. but If I unplug the inverter from the circuit, the TV still flashes green 15 times green then off. does this mean its not the inverter, or the tv is going into protection mode again without it?

And insight or help I would so much appreciate. I can post any pictures if need be. Thanks, Roger

[tom66]

Re: Emerson lc407em1 Turns on screen only flashes, then off

The inverter board doesn't feed back an error signal to the main board on most TVs (I only know of Sony and Panasonic LCDs that do this), so you may be looking more at a power supply or main board fault. In order to tell you more, we will need pictures of the chassis layout.

[proaudiosoft]

Re: Emerson lc407em1 Turns on screen only flashes, then off

ok, thanks tom. I am off tommorow and will def post some pics. definately so appreciate it

[proaudiosoft]

Re: Emerson lc407em1 Turns on screen only flashes, then off

The inverter board doesn't feed back an error signal to the main board on most TVs (I only know of Sony and Panasonic LCDs that do this), so you may be looking more at a power supply or main board fault. In order to tell you more, we will need pictures of the chassis layout.

Here are a few pics of the layout.... Thanks

[tom66]

Re: Emerson lc407em1 Turns on screen only flashes, then off

Oh dear. This is not a very well made TV.

Do you have a digital multimeter?

If you don't: Beg, borrow or buy one, you will need it to test things.

If you do: On the left hand side of this picture is the inverter board. Turn the TV on. Place your black multimeter probe on the chassis. Set meter to 200VDC and make sure red probe in VOLT, black probe in COM. Then look at the connector on the power supply whcih goes to the inverter. Probe each pin starting from the red ones, numbering as you go up. Tell us what your meter reads.

Note -- Do not touch any part of the power supply while the unit is plugged in or shortly after power off.

[proaudiosoft]

Re: Emerson lc407em1 Turns on screen only flashes, then off

Yes I have an volt/ohm meter, esr meter and other testing equip. I just noticed D1208 is missing off the power board. the fuse was missing to when I received this tv so, looks like someone else was working on it. Also the board looks like D1208 burnt. I am going to order a new diode. I remember reading that exact diode beeing faulty on another with the same model as mine. could be the culprit for sure. I read that last night, I believe you gave input on that nicely Any advise on anything else I should check before replacing the diode? Thanks tom..... Roger

Oh, the inverter I tested that connector last night. Oh, I will check the inverter again and let you know too. It look like the voltages were good last night, from what I could read on the power board at the connector pins anyway

[budm]

Re: Emerson lc407em1 Turns on screen only flashes, then off

I would inspect that power supply board real close at the bottom side to see if any works are done to it, check those diodes in circle. That large 450VDC cap should have 160VDC on standdby, about 380V when powered on.
Also report the voltage readings on that white multi-pin connector on the top right of the power supply board that goes to the other board, there are labels by the pins of the connector.

[proaudiosoft]

Re: Emerson lc407em1 Turns on screen only flashes, then off

I would inspect that power supply board real close at the bottom side to see if any works are done to it, check those diodes in circle. That large 450VDC cap should have 160VDC on standdby, about 380V when powered on.
Also report the voltage readings on that white multi-pin connector on the top right of the power supply board that goes to the other board, there are labels by the pins of the connector.

I dont see anything else messed with in the power supply but the one zener diode removed. The diodes you circled I just checked again, they seem ok (.400 to .950 and open the other direction, no shorts).
The pin connector readings are as follows:
tuner+35v = 41v
lcd + 12v = 12v
lcd + 12v = 12v
power on + 3.5v = 3.5v
power on + for tv 6.5v = 9v
power on + 3.5v for reg = 5.5v
24v for amp = 27v

The Large Cap you told me to test is 38v standby 11v on (tested on jumper near it). The D1208 diode seems to be missing like I said, I ordered it, but I do recall someone in another thread on a similar tv with the same PS telling them they are better off leaving it out.

Any help continuing appreciated much

[budm]

Re: Emerson lc407em1 Turns on screen only flashes, then off

"The Large Cap you told me to test is 38v standby 11v on" That cannot be right. Is the meter in DC? The Negative leg of that cap the primary side ground ref for the primary circuit , you cannot use the chassis ground as the ref.

[proaudiosoft]

Re: Emerson lc407em1 Turns on screen only flashes, then off

"The Large Cap you told me to test is 38v standby 11v on" That cannot be right. Is the meter in DC? The Negative leg of that cap the primary side ground ref for the primary circuit , you cannot use the chassis ground as the ref.

Meter in AC. I was using the TV chassis as ground though. Using the line in ground as ground I get 6.5 in standby, and 60v with power on. Is this ground ok?

[budm]

Re: Emerson lc407em1 Turns on screen only flashes, then off

No, you need to get to the trace that is connected to the negative leg of that cap, you cannot use the chassis for the ground ref point since that cap is in the primary side (deadly side, so DO NOT TOUCH anything in the hot section).
Chassis is the ground ref point for the cold side of the circuits.
Meter set to DC.

[proaudiosoft]

Re: Emerson lc407em1 Turns on screen only flashes, then off

No, you need to get to the trace that is connected to the negative leg of that cap, you cannot use the chassis for the ground ref point since that cap is in the primary side (deadly side, so DO NOT TOUCH anything in the hot section).
Chassis is the ground ref point for the cold side of the circuits.
Meter set to DC.

Of course. I have 5v stby, and 347 on

[proaudiosoft]

Re: Emerson lc407em1 Turns on screen only flashes, then off

Anything?

[proaudiosoft]

Re: Emerson lc407em1 Turns on screen only flashes, then off

received diode today. gonna install and post results ...

[proaudiosoft]

Re: Emerson lc407em1 Turns on screen only flashes, then off

no change after installing diode. turn on, green light flashes 15 times, then powers off to red light. screen flashes on then off after around the 13th green light flash. I did notice if I disconnect the inverter the green light will flash 19 times, then steady on for a sec or two, then back to red light. is it possible the inverter is the problem, and the tv turns off without it?

[budm]

Re: Emerson lc407em1 Turns on screen only flashes, then off

We will have to locate the diagram next, unless someone in the forum had fixed this same board before.

[proaudiosoft]

Re: Emerson lc407em1 Turns on screen only flashes, then off

We will have to locate the diagram next, unless someone in the forum had fixed this same board before.

here are a couple...

[budm]

Re: Emerson lc407em1 Turns on screen only flashes, then off

OK, I have seen this circuit before:
https://www.badcaps.net/forum/showth...erson+lc407em1

[budm]

Re: Emerson lc407em1 Turns on screen only flashes, then off

I look at the diagram, so far your 5v and PFC Voltage booster (345V) are working. I need to read the manual to figure out the flashing LED codes. The circuit has sensing PROTECT1, PROTECT3, cannot find PROTECT2 yet, need to find out if one of them is bad or not.

[tom66]

Re: Emerson lc407em1 Turns on screen only flashes, then off

If you get the FUNAI part number for this board (begins with BA9) I may be able to find a schematic, if you don't already have one.