Akai LCT3201AD

[trains58554]

Hi guys,

I have an Akai LCT3201AD tv that is not working quite right. We have already replaced all the caps on the power supply bord and a few on the main board. Which gave the tv some more live but it does not stay on.

It gets all the way to flashing the logo for about a half second and then the power supply shuts down that is also when the backlight first turns on.

Thanks

[budm]

Re: Akai LCT3201AD

Look under the black heat sinks to see if there are more caps under the heat sink. These MAGMEET POWER SUPPLY board like to put caps under the heat sink, which is bad idea.
http://s807.photobucket.com/albums/y...98A%20REV1_4C/
Check and see if the 24V power supply is still putting out 24vdc when the backlights go out.

[trains58554]

Re: Akai LCT3201AD

Hi budm,

We have replaced all the caps even the ones under the heat sinks. When the backlights go out it turns the power supply off and we no longer get 24V.

[budm]

Re: Akai LCT3201AD

OK the 24V went into shutdown due to either it detects shorted circuits in the inverter board or it is told to shutdown by the main board.
So disconnect the cable to the inverter board and see if the 24V will stay on or not.
Can we see good pictures of how all the boards are connected together?
We also need to lacte the PS_ON pin on the power supply board to see if that signal goes away at the same time as the 24V.

[trains58554]

Re: Akai LCT3201AD

Ok I do remember us checking to see if the power supply stays on with the inverter power disconnected and it does stay on. I also got some more pictures.

Thanks

Jay

[tom66]

Re: Akai LCT3201AD

The 24V drops out with the inverter connected, but is OK with no inverter?

[trains58554]

Re: Akai LCT3201AD

Yep that is exactly what is happening.

[tom66]

Re: Akai LCT3201AD

Can you get hold of some car headlamp bulbs and try wiring two in series across the 24V, and see if it drops out as well? Not sure about US, but car headlamps in UK are 65W, so that's a modest load on the inverter output (though for a 32" full load is around 130-150W...)

[budm]

Re: Akai LCT3201AD

Do you have #921 (12v, single element car lamp)? Put them in series and hook it up the 24v terminals and ground terminal on the power supply board and see if they will stay lit.
Or use 1157 low element of each bulb in series first.
http://www.run-n-lites.com/bulbspec.asp

[Jahson]

Re: Akai LCT3201AD

On the last picture power board im not sure but the 2 caps in the bottom left look bugled. Could be the light reflection.

[trains58554]

Re: Akai LCT3201AD

Hi

I looked and did not find any car lamps. Is there anything else I can use to test it?

@Jahson, in the last photo thoese two caps are bad as that is an early photo I just posted it so you and others can see the labeling for the white connector.

Thanks

Jay

[budm]

Re: Akai LCT3201AD

You can use 75Watts 120V lamp, its cold resistance is about 12 Ohms, try using it as a load for now.

[trains58554]

Re: Akai LCT3201AD

I could only find a 60W 120V bulb. I tried that as load and it did not shut down. I also was able to test if the PS_ON power went away after the 24v drops out and yes it does.

Jay

[budm]

Re: Akai LCT3201AD

Try two lamps so it will have more load.

[trains58554]

Re: Akai LCT3201AD

in series?

[budm]

Re: Akai LCT3201AD

In parallel

[trains58554]

Re: Akai LCT3201AD

Ok I tried that and the first 2-3 times it just shut down then it turned on and stayed on. I also heard a hissing sound from the power board.

[budm]

Re: Akai LCT3201AD

OK, we need to look at the inverter board next. That is the darn DARFON board. Please take good closed up pictures of the whole board and then the small sections like 1/4 each so I can see the components and labelling clearly.

[trains58554]

Re: Akai LCT3201AD

Ok I got some more pictures.

[budm]

Re: Akai LCT3201AD

By the way, you already checked all the fuses on the inverter board?