Magnavox 42mf231d/17

[gorr35]

When my Plasma TV (Magnavox 42mf231d/17) wasn't getting any power....just clicking relays. I figured replacing the bulging capacitor (1500uf 10v) on the power supply board would fix it. After replacing it, still nothing....until I came across another cap on the Y-Sustain Board. This one I noticed is bulging also but it seems to be leaking from the bottom and running down the PCB as you can see in the blurry picture, I circled the cap in question in yellow. Can someone please tell me how to take this board out? I removed the screws and cables but something is still holding it down tight. Could it be the large heatsinks? Are they attatched from the bottom side? If so how do I get those off without having to take everything apart just to get to them? Plus would a bad cap on the Y-Sustain board cause no power at all?

[hoadle]

Re: Magnavox 42mf231d/17

Are you check the fuse at quick disconnect cable?
Here the service manual for you TV (Magnavox 42mf231d/17 & Magnavox 42mf231d/37) they can show you how
http://www.mediafire.com/?qwtwzmmjy2f

[PlainBill]

Re: Magnavox 42mf231d/17

When my Plasma TV (Magnavox 42mf231d/17) wasn't getting any power....just clicking relays. I figured replacing the bulging capacitor (1500uf 10v) on the power supply board would fix it. After replacing it, still nothing....until I came across another cap on the Y-Sustain Board. This one I noticed is bulging also but it seems to be leaking from the bottom and running down the PCB as you can see in the blurry picture, I circled the cap in question in yellow. Can someone please tell me how to take this board out? I removed the screws and cables but something is still holding it down tight. Could it be the large heatsinks? Are they attatched from the bottom side? If so how do I get those off without having to take everything apart just to get to them? Plus would a bad cap on the Y-Sustain board cause no power at all?

Good pictures, thanks.

Probable diagnosis: One of the chips on the Y-buffers has shorted, taking out a driver transistor on the Y-Sustain. This overloads the power supply. A simple test is to unplug the power cable to the Y-Sustain and see if the TV powers up. You won't get any picture, but you should get sound.

The expensive fix is to replace both Y buffers and the Y sustain. Figure $80 each for the buffers and the sustain.

The cheap fix is to replace all 12 buffer chips, the shorted transistor, and the leaky cap. The buffer ICs run about $10 each, the transistor is about $7, and the cap about $1.00.

Or you could recognize that a new 1080P plasma TV could cost under $500.

More information on the buffers and sustain problem can be found on the Coppell TV repair blog.

PlainBill

[gorr35]

Re: Magnavox 42mf231d/17

OK PlainBill I tried disconnecting the power cable from the Y-Sustain and same thing. Won't power on....just clicking from what sounds like the relay on the OFPB (Pictured) also still no lights at all from the power button. I guess I need to invest in a good Multimeter.....preferably one that reads high microfarad caps, like 0.5 - 2000uf or higher.

[PlainBill]

Re: Magnavox 42mf231d/17

OK PlainBill I tried disconnecting the power cable from the Y-Sustain and same thing. Won't power on....just clicking from what sounds like the relay on the OFPB (Pictured) also still no lights at all from the power button. I guess I need to invest in a good Multimeter.....preferably one that reads high microfarad caps, like 0.5 - 2000uf or higher.

Well, it's possibly not a capacitor problem. Here's the usual start-up sequence..

1. The TV is plugged in, the power supply is providing 5V standby. The standby processor is waiting for someone to hit the power button, either on the remote or the top of the TV.
2. The power button is pressed. The standby processor does a few simple tests and turns on the main power supply. It then begins monitoring the voltages out of the power supply, as well as voltages generated on the main board. If any of them are out of spec, it shuts down the main supply.
3. When the supply voltages are all stable the standby processor starts the main processor, which performs a self test, then initializes the display. If IT finds a problem it may command the standby processor to shut down the power, or it may continue operating.

In any case, the next step would be to check if any of the power supply voltages are missing when the power supply turns on.

PlainBill

[gorr35]

Re: Magnavox 42mf231d/17

Well PlainBill I will consider everything you suggested and will check those. An electrician came by to fix my heater and he saw me pulling one of the fuses out of the tv (as Hoadle suggested) so he offered to check them with his meter. He checked them all and said one of them was shot.....it happens to be the one on the power supply board. I couldn't read the tiny markings on it but I believe it's an 8amp 250v ceramic fuse. What would cause the fuse to blow? A number of things? I'm assuming with my limited experience that replacing the fuse isn't going to fix the problem because a bigger problem caused it to blow in the first place? I will check or have someone check what you suggested but if I can't fix it cheap then I will sell it for parts.

[mushu1430]

Re: Magnavox 42mf231d/17

PlainBill, I have a similar problem, My tv powers up, the power light stays on, get the two clicking relays no picture or sound at all. I also had the same capacitor on the y main leak out and i replaced it. Checked all the voltages(vs,va,vscan,ect), all of them are into spec with whats on the board. All my fuses are fine. Stumped, any help would be great.

[mushu1430]

Re: Magnavox 42mf231d/17

PlainBill, I have a similar problem, My tv powers up, the power light stays on, get the two clicking relays no picture or sound at all. I also had the same capacitor on the y main leak out and i replaced it. Checked all the voltages(vs,va,vscan,ect), all of them are into spec with whats on the board. All my fuses are fine. Stumped, any help would be great.

For some reason now when the y main is plugged into the pcb the vscan jumps up to 250 and stays there if i unplug it it goes back to 190 where it belongs

[PlainBill]

Re: Magnavox 42mf231d/17

For some reason now when the y main is plugged into the pcb the vscan jumps up to 250 and stays there if i unplug it it goes back to 190 where it belongs

That indicates a problem with the Y-Sustain. In another thread I have referred to a Coppell TV Repair blog that describes the problems with the sustain boards for the plasma panel in this TV. The gentleman describes a technique for identifying shorted buffers and a shorted sustain.

I have said it repeatedly, many of the problems found in plasma tvs are well within the skill level of 'do it yourself' electronics repair. I've dealt with bad caps in the power supply, bad switches in the DC-DC converter, bad main logic board, dead power supply, and failures of the Z-Sustain on the LG 3x? panel. All of them can be easily and economically repaired. Spending $10 - $90 for parts to repair a 42" plasma makes sense. I can't justify spending $240 given the low price of new plasma TVs.

[Popov]

Re: Magnavox 42mf231d/17

Please help. Can anybody tell me parameters of C281 capacitor which is on main power supply board and under heat sink with s/n steaker? Mine is burnt-out.

[gorr35]

Re: Magnavox 42mf231d/17

Please help. Can anybody tell me parameters of C281 capacitor which is on main power supply board and under heat sink with s/n steaker? Mine is burnt-out.

Not trying to be rude but why are people posting questions in my thread rather than creating their own?

[Popov]

Re: Magnavox 42mf231d/17

Not trying to be rude but why are people posting questions in my thread rather than creating their own?

Sorry, I just have exactly the same TV with the same problem. To continue investigation I need to fix the capacitor problem first. Then I can provide results of my investigation with possible working solution which hopefully can help you and other people.

[Popov]

Re: Magnavox 42mf231d/17

Can someone please tell me how to take this board out? I removed the screws and cables but something is still holding it down tight. Could it be the large heatsinks? Are they attatched from the bottom side? If so how do I get those off without having to take everything apart just to get to them?

gorr35, there is a big soft robber like compound under the board. To remove the board you have to pull the board very slowly from the chassis. I recommend to disconnect both upper and lower Y-buffer boards first before removing the board.

[gorr35]

Re: Magnavox 42mf231d/17

Please help. Can anybody tell me parameters of C281 capacitor which is on main power supply board and under heat sink with s/n steaker? Mine is burnt-out.

If your board is the same as mine then I don't see the C281 in question.....maybe an uploaded picture would help.

[Popov]

Re: Magnavox 42mf231d/17

If your board is the same as mine then I don't see the C281 in question.....maybe an uploaded picture would help.

Here is a picture. The C281 cap is right under the red arrow next to the big white resistor and another C280 blue high voltage cap.

[gorr35]

Re: Magnavox 42mf231d/17

If you are refering to the blue ceramic cap, I believe that is a 0.22uf 25v.

[Popov]

Re: Magnavox 42mf231d/17

If you are refering to the blue ceramic cap, I believe that is a 0.22uf 25v.

The cap is not showing on the picture since it's under the aluminum heat sink, almost touching a heat sink black IC. Mine was completely burnt out so I don’t know color or even form. If this is a cap which is the closest to the heat sink and right next to C280 2200pF 1 kV one, this is the one I am looking for! Thank you very much!!! I will let you know what I will find since I have a problem with Y-sustain too.

[gorr35]

Re: Magnavox 42mf231d/17

The cap is not showing on the picture since it's under the aluminum heat sink, almost touching a heat sink black IC. Mine was completely burnt out so I don't know color or even form. If this is a cap which is the closest to the heat sink and right next to C280 2200pF 1 kV one, this is the one I am looking for! Thank you very much!!! I will let you know what I will find since I have a problem with Y-sustain too.

Yes that is the one i'm talking about.....it looks similar to the one pictured.

[Popov]

Re: Magnavox 42mf231d/17

Yes that is the one i'm talking about.....it looks similar to the one pictured.

Is it marked as 224 25V, 224 250V or 222 250V?

[Popov]

Re: Magnavox 42mf231d/17

Is it 25V or 250V?