Magnavox 46ME313V/F7 powers on and off

[cory1108]

Can anyone help me trouble shoot a magnavox 46me313v/f7. I am very much a novice when it comes to tv repair but have fixed a couple for myself and friends. Original issue was when u plugged in the indicator light would flash continually so I suspected bad components on power board. I purchased a used power board and when installed the tv would then start up as soon as u plugged into power would stay on 10-15 seconds then power off and repeat until power was disconnected. The only way I could keep it from continually powering off and on was to disconnect the connector for the ir sensor board. If i disconnect then reconnect it goes into standby mode. If u hit power button it starts doing same thing. Any ideas as to what could cause this issue?

[cory1108]

Re: Magnavox 46ME313V/F7 powers on and off

Please.... anyone have any ideas that can help??

[budm]

Re: Magnavox 46ME313V/F7 powers on and off

https://www.badcaps.net/forum/showthread.php?t=39740

[HiDesertRat]

Re: Magnavox 46ME313V/F7 powers on and off

Post the pictures! Bud can do wonderful things with them!

I am just getting into this stuff, but I would suspect the IR board or even the remote. Is there something sending a constant signal to the IR board telling the tv to turn on and off?

Tried to find a wiring diagram for your set but couldn't find one for that model number. Does your TV have a On/Off button? Does it make a difference if you use the panel button or the remote?

You disconnect the IR board, plug in the TV and it goes to standby, right? If I read the diagram of the set I was looking at correctly, when you use the panel On/Off button it applies a ground to pin 6 of the connector. If your button was stuck, it would have a ground there all the time. Thus, turning the set on and off. It is just a shot, but check the button out.

If that isn't it. Maybe you can leave the IR board disconnect and manually apply a ground to the pin to see if the set will come on and stay on. Don't leave the ground connected, it is just supposed to be a momentary application of ground.

[cory1108]

Re: Magnavox 46ME313V/F7 powers on and off

I will post pics asap, in mean time I do have schematics. They should be attached if they upload properly.

[cory1108]

Re: Magnavox 46ME313V/F7 powers on and off

And to partially answer your question HidesertRat; the function board feeds into the ir board and then into main board. I can disconnect the function board and it has no effect. Have to disconnect the ir board before anything changes. My initial thought was a bad ir board but I'm not sure what to test to make sure before I order replacement

[budm]

Re: Magnavox 46ME313V/F7 powers on and off

OK, let me download the service manual and study them.
So far shopjimmy does not show any boards for your TV for me to look at.

[cory1108]

Re: Magnavox 46ME313V/F7 powers on and off

Here are pics of boards

[budm]

Re: Magnavox 46ME313V/F7 powers on and off

OK, we can try killing the output signal for the IR receiver output by shorting pin 1 and pin 2 of the IR receiver and see if the problem will go away.

[HiDesertRat]

Re: Magnavox 46ME313V/F7 powers on and off

Cory, this TV does look very much like the Emerson I am working on. May have the same problem, may not.

@Bud: You are helping us both, so hopefully, you don't get confused as the symptoms seem to be the same. On mine, I did disconnect the 9 pin ribbon cable on the main, basically taking the IR and front panel out of the loop. Then shorted pin 6 and 7, momentarily, on the main (like when you push the on button). Results were the same. TV came on, 5 seconds later, it went to standby. Would that work here? Should it have worked on mine?

@Cory: Listen to Bud, he is the expert here. I, like you , am just trying to learn my way around in these things. I have experience in electronics, but TV theory is not my strong suit.

[budm]

Re: Magnavox 46ME313V/F7 powers on and off

On this may have the IR receiver problem, so lets try killing the IR signal first.

[cory1108]

Re: Magnavox 46ME313V/F7 powers on and off

Shorted pins 1 & 2 and there was no change. Continued to power on and off

[budm]

Re: Magnavox 46ME313V/F7 powers on and off

OK, check the resistance between pin 1 (3.3V) and pin 7 (GND) to see if it shows low resistance, the check the DC Voltage on the same two pins to see if it shows 3.3VDC.
BTW, TV unplugged.

[cory1108]

Re: Magnavox 46ME313V/F7 powers on and off

3.238v what range should resistance be?

[budm]

Re: Magnavox 46ME313V/F7 powers on and off

I expect it to to be >500 Ohms.
It is strange that if you disconnect the IR, the will not be cycling which point the problem from the IR is sending erroneous signal to the main board, but we ground out the IR signal and it is still doing the same thing. It does not make any sense at this point. We also know that it is not form the switch board since you disconnected it and it still doing the same thing.
OH, and what Voltage do you get at pin 5 (remote pin) when you grounded out the IR signal?

[cory1108]

Re: Magnavox 46ME313V/F7 powers on and off

Let me check again but I got 54 ohms

[cory1108]

Re: Magnavox 46ME313V/F7 powers on and off

56.6 ohms

[cory1108]

Re: Magnavox 46ME313V/F7 powers on and off

Disconnected 9 pin connector and it went to 61 ohms

[budm]

Re: Magnavox 46ME313V/F7 powers on and off

That means the resiStance at pin 3 (VCC) of the IR receiver MUST BE <1 Ohm. Check the resistance on pin 3 and ground of the IR RECEIVER. Cap 4051, or 4056, or the IR is shorted.
https://www.badcaps.net/forum/attach...3&d=1415336886

[cory1108]

Re: Magnavox 46ME313V/F7 powers on and off

Pin 3 is 268 ohms