Magnavox 42mf439b/f7 not powering on.

[MCNorris]

My tv suddenly wont turn on, the standby light is on and there's a slight click when you plug it in other than that nothing. The board is BA94H0F0103 2 A. Can't find much info about it, if anybody can help I'd really appreciate it.

[selldoor]

Re: Magnavox 42mf439b/f7 not powering on.

Pictures might help? Tested ALL the fuses.

See here https://tvrepairtips.org/philips-a94...v-power-supply

If that is guaranteed working at $20 sounds a bargain!

Not that we know for sure if yours is faulty

[MCNorris]

Re: Magnavox 42mf439b/f7 not powering on.

I tested the fuse and none of the caps look bad here's a picture of the board

[selldoor]

Re: Magnavox 42mf439b/f7 not powering on.

Suscon Caps may be suspect even though they dont look bulged.
Any bulged caps on the Main/logic Board - picture? any fuses?

If the power light is on that suggests you have 5 volts. Can you test the voltages being output from the power supply board. I cant see any indication
on the board of what they should be - perhaps you can see? If not set your meter on 200vDC and test each pin and list the results. Black Probe fixed to a
ground screw probe each pin with red probe. If less than 20vdc on all then
reduce the setting to 20vdc to get a more accurate result.

As you are a new poster I would ask you to take care there are voltages that can kill.
So dont touch anything else on the board until asked to.

[Caleb]

Re: Magnavox 42mf439b/f7 not powering on.

That board has a gob of zener diodes, since you have standby your primary is probably ok. Using a multimeter in diode mode I would check every one of those zener diodes if you get a solid beep on any one lift a leg off board and see if the diode tests bad or you have a short on board. I circled all the ones I could see with the primary suspect in my mind the one circled in yellow and red in the top right corner. These have a bad habit of failing on these cheap power supplies. And since you are new here testing is done with the tv UNPLUGGED.

[MCNorris]

Re: Magnavox 42mf439b/f7 not powering on.

I tested the power output and got red 4.3; black -4.3; white -4.3.

I have a pretty cheap multimeter without a buzzer I'm not exactly sure how to test a zener, continuity? sorry I'm new to some of this.

[selldoor]

Re: Magnavox 42mf439b/f7 not powering on.

I tested the power output and got red 4.3; black -4.3; white -4.3.

I have a pretty cheap multimeter without a buzzer I'm not exactly sure how to test a zener, continuity? sorry I'm new to some of this.

Not sure what you have tested there. You should have been testing the
voltage going to the logic/main board - perhaps the gray flat cable bottom right in your picture. We need more pictures showing what lead goes where.

If you have not done any electronic repairs on computers/ monitors then a tv
may be a step too ambitious, not to mention dangerous.

Suggest you read this - relates mainly to monitors but there is a lot of test information in there including a diode. You can also find how to test things by googling " How do i test a ******** with a multimeter."
https://www.badcaps.net/forum/showthread.php?t=10419
Start at post 19

[MCNorris]

Re: Magnavox 42mf439b/f7 not powering on.

Thanks a lot for the link, here's a few more pictures. I'm semi familiar with this stuff just not to this level, I'm a diesel mechanic and I've not messed around much with any non-auto electronics really.

[selldoor]

Re: Magnavox 42mf439b/f7 not powering on.

Ha! well I dont know a lot about Tvs - the board you have shown us so far does have a power supply on it but I think the proper power supply is the one part showing on the top left of the middle picture. Can you post full a picture of that board

[budm]

Re: Magnavox 42mf439b/f7 not powering on.

Please show the whole back side of the TV so we can see how all the boards are connected together. This TV has master power supply (where the power cord is connected to) and the sub-power supply.
See if these are the boards you have in your TV.
http://www.shopjimmy.com/catalogsear...navox+42mf439b

[MCNorris]

Re: Magnavox 42mf439b/f7 not powering on.

That board is the one I posted first

[MCNorris]

Re: Magnavox 42mf439b/f7 not powering on.

Here's a picture of the whole back, it has all the board on that webpage

[selldoor]

Re: Magnavox 42mf439b/f7 not powering on.

We really need good clear pictures of YOUR board.

Looking at other boards can sometimes help but it is akin to the chap who went to the doctors as he has a pain, and the doctor says "we will need to take some xrays to help diagnose the problem." The patient replies - "no need,
my brother had a similar pain and I have brought in the xrays he had done.

[budm]

Re: Magnavox 42mf439b/f7 not powering on.

This is going to tough since none of the connectors has any labels on them to show the pin function. The standby power supply is OK, but cannot tell if the PS_ON signal is present or not.

[Andrew F. Ali]

Re: Magnavox 42mf439b/f7 not powering on.

SELLDOOR-Think I'll use that X-ray diagnosis joke in a meeting I have to attend in a bit. Hee! Hee!

[MCNorris]

Re: Magnavox 42mf439b/f7 not powering on.

All these pictures are of my tv

[selldoor]

Re: Magnavox 42mf439b/f7 not powering on.

All these pictures are of my tv

I know that but the only really clear one of the main power supply is the shopJimmy one

Can you spot what might be wrong with this section of your board

[MCNorris]

Re: Magnavox 42mf439b/f7 not powering on.

Ok I get ya, I can't get a very good picture of the whole tv as I have to hold the camera up pretty far. I'll retake pictures of each board the picture of the whole back was more for reference of how everything was hooked up like budm asked for.

[MCNorris]

Re: Magnavox 42mf439b/f7 not powering on.

Here's some more pictures hope they are clearer.

[selldoor]

Re: Magnavox 42mf439b/f7 not powering on.

Yes they help a bit - on th epicture in post 2 topleft corner there are two links
labelled power on Hi and Power on H2 . With your meter on 20vdc put black on a ground screw and test for a voltage on the links. Do not touch the heatsink.
Did you work out how to test all those diodes? does your meter have a diode test - will have a diode symbol on the selector if it does.