Magnavox 42MF230A No Picture, Model info?

[XtraETN]

Hey! I've been reading around these forums for a bit. I'm about to buy a 42" Magnavox 42MF230A. The guy is selling it for 20$ and the plasma turns on but theres no picture as it seems.

Does anyone know anything about this model? Would it be a good deal if its a cheap repair? thanks for the input!

[XtraETN]

Re: Magnavox 42MF230A No Picture, Model info?

Any input anyone?

[Nocta]

Re: Magnavox 42MF230A No Picture, Model info?

I've got no much experience with tvs but I guess that a lot of things could cause something like that.

$20 doesn't seem like much. I'd buy it and try.

[tibimakai]

Re: Magnavox 42MF230A No Picture, Model info?

Most likely buffer boards/Y-sus board which can be expensive . It's probably a Philips.

[cliff_hootarski]

Re: Magnavox 42MF230A No Picture, Model info?

Looks like the guts are Samsung.

http://www.shopjimmy.com/catalogsear...lt/?q=42MF230A

Does it have sound?

[XtraETN]

Re: Magnavox 42MF230A No Picture, Model info?

I think i might of phrased the problem wrong. I meant the tv wont switch on. Im guessing stuck on standby? Im picking up the tv in a few minutes

[XtraETN]

Re: Magnavox 42MF230A No Picture, Model info?

Alright so I got the TV. The previous owner said that it wouldn't turn on, but after clicking the power a few times got the picture showed up one, but then soon after it wouldn't turn on again. Does it sound like a capacitor problem? I opened it up but see no bulging or blown capacitors. So now I'm lost ;(

The first thing I noticed as soon as i plugged in the panel, the red power LED turned on. Seems strange to me that the light would always stay on even with the TV off. I can't seem to turn it off either, pressing all the buttons.

I press the power button and hear the relay click and the red light turns blue, however nothing on the screen turns on. Pressing the power button again turns the blue light back to red.

Any help would be appreciated! I have small to moderate knowledge of circuits though. Thanks! I uploaded pictures of the boards in the panel, if you need more close ups i'll be glad to include them!

[tibimakai]

Re: Magnavox 42MF230A No Picture, Model info?

the picture is clear?
The heatsinks on the buffer boards are hot or warm?

[XtraETN]

Re: Magnavox 42MF230A No Picture, Model info?

when you say the buffer boards do you mean the board in picture 3? If so, then yes after leaving on the panel for a few minutes (blue LED on), the bigger heat sinks seems very hot.

[XtraETN]

Re: Magnavox 42MF230A No Picture, Model info?

I measured the output voltages from the power supply and got

Va = 71V
Vscan = Negative Oscillating between 0 -180?
Vs = 206
Ve = 84.7V
Vset = oscillating between 198.0 - 198.3

All the voltages look good except for Vscan.
Is Vsc the same as Vscan?

What would this voltage oscillation mean? Would it still lead to a burnt IPM on the Y-Sustain board?
Touching the heat sinks, they seem very hot. However I didn't touch the largest one yet (not shown in any of my photos) that was under the panel holder bar so not sure about that one. It was a pain trying to remove the Y-sus board an I don't want to place it back yet in risk of damaging those ribbon cables leading to the screen I think.

[tibimakai]

Re: Magnavox 42MF230A No Picture, Model info?

the six little ones on each board(total 12) on the third picture. there is an upper and a lower Y buffer board. Each controls half the screen.

[XtraETN]

Re: Magnavox 42MF230A No Picture, Model info?

yes the ones on the buffer board did also feel hot to the touch.

[tibimakai]

Re: Magnavox 42MF230A No Picture, Model info?

When I changed the buffer board on two previous 42" philips TVs the little heatsinks were almost cold.
See if this helps you:
http://blog.coppelltvrepair.com/2010_03_01_archive.html

[XtraETN]

Re: Magnavox 42MF230A No Picture, Model info?

I'm confused on which pins I'm suppose to measure?

[Nocta]

Re: Magnavox 42MF230A No Picture, Model info?

I guess he means this entry: http://blog.coppelltvrepair.com/2010...er-boards.html

Seems pretty clear to me which pins you should measure.

[tibimakai]

Re: Magnavox 42MF230A No Picture, Model info?

In my beginner opinion, if do you fill hot heat sinks on those two boards, you need to replace them.
Then you can have the Y sus board bad too.
On my TVs that I have repaired I had picture all the time, there were some pinkish staticy horizontal lines, so the buffer chips were not shorted yet.
If you don't have picture, then most likely you have shorted buffer chips and they may have damaged the Y sus board too. Usually it's recommended to replace all three together. Read on that connel site about this. There is a guy on Youtube showing how to replace these chips. Not easy, I have tried it.

[XtraETN]

Re: Magnavox 42MF230A No Picture, Model info?

Well I found the burned out IC chip on the Lower buffer board left with alot of burnt residue on the top of it.
I tested that Top buffer board and there seems to be no shortages and its still working, I'm guessing.

I don't think replacing the IC now is an option since it looks burnt through the pcb. So now the only option is to replace the Lower board.

Question now, is there a problem with the Y-main board which would of caused the burned IC? and what should I test for to check that the Y-main is still working.

Is there a way to test the main chip on the Y-main?
I'm also currently testing for shorted resistors, diodes, and other components.

I found one opened fused in the photo shown below. Anyone know what component could of caused this blown fuse?

[tibimakai]

Re: Magnavox 42MF230A No Picture, Model info?

I never worked on a Y sus board before, so I can't help there, but I would check all the Fet transistors for short, diodes, fuses, maybe even capacitors.
So just to be clear, you don't have a picture right?
Y upper buffer board controls the upper half of the screen and the lower the lower half of the screen. Each half is divided in six, as how many chips do you have on a buffer board.
What I have read on these and other forums, that if a buffer board is shot, the Y sus board is bad too.
I would like to learn how to repair Y/X sus boards myself. I know that there is pretty big component(box looking) with a big heatsink on it and in that a diode is usually blown.
Look here maybe you learn something:
https://www.youtube.com/results?sear...l0l83l83l1l1l0.

[XtraETN]

Re: Magnavox 42MF230A No Picture, Model info?

Heres pictures of the Y-sus board.

I meant to say the open fuse I found in the previous post was on the Y-main board.

How do you test a fet and transistor?

I don't see any blown/bulging capacitors, still testing a few resistors. Diodes seem to be fine. A found the big chip under the giant heatsink for about 10-20$ on ebay so should be easy to replace. But is there a way to check it if it is shorted?

[selldoor]

Re: Magnavox 42MF230A No Picture, Model info?

I dont know how new you are to this but can I just say I hope when you are feeling how hot heatsinks are that (a) they are often meant to be hot, that is how they work. and more importantly (b) I hope this touching is with the power off for 5 minutes or so. Remember you are dealing with a Faulty TV and the heatsinks can in any case carry a voltage that will give you a nasty jolt. If the power is on and you get jolted onto the primary circuit ??? - nasty.