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  Topic Review (Newest First)
09-26-12 04:42 AM
Spannerz
Re: The Magnavox 42mf337b LCD repair thread

MASSIVE BUMP

THIS IS FANTASTIC!

There are dozens of forums with the fault of "whining" philips/magnavox pfl... power supply, none with a fix. This is awesome, and I hope somehow people will link to from these other sites, and I will probably do that also.

I did this exact same (very similar) fix for a power supply in a lift system! years ago, even removed the burnt out transformer, diodes pre-stage components and installed an external power supply. But I never even once thought of doing it to fix my TV. (I will probably be preforming this surgery with 2x 12v car batteries tomorrow! haha)

Please, can you write a detailed explanation, in a final summary post, describing the steps taken, what was removed and what was installed. (Is it possible to use a smaller power supply?) This will help many people on many forums, with many dead magnavox/philips TV's.

Thanks mate you've just re/opened my eyes.

TAGS: 715T2432-2 715T2432-3 ADPF24300R1P philips magnavox 42PFL7422 whining buzzing power supply TPT1.2a la
01-16-12 10:05 AM
lcaillo
Re: The Magnavox 42mf337b LCD repair thread

Just of the record, Home Theater Shack does not recommend users add external power supplies to a unit in this manner. There are many potential problems that one could encounter and many safety issues involved. We do not restrict users sharing experience, but we cannot make recommendations that have a high probablility of creating safety and functional hazards.



01-15-12 09:02 AM
jeffescortlx
Re: The Magnavox 42mf337b LCD repair thread

Quote:
colonelget wrote: View Post
I hate to bump an old thread but I was just wondering if anyone was ever to find a solution to this problem. I'm having the same "chirp" issue. I'm an electronics novice. I can test some components with a meter and solder but that about it. I ordered a "repair kit" for the board off ebay it came with replacement caps for C953 C952 C951 and C955. It also had 2 replacement diodes for ZD902 and ZD904. I replaced all the components but i still have the chirp and no picture.
Yes I did find a solution to this problem. After swapping half the parts on the 24v side of the power supply, and it was still chirping and squeeling, I gutted it. I installed a meanwell 350 watt 24v power supply and tied it into the 24v side. I left the 12v section alone.
It still works great to this day. No more noise.

But, you need to do some test to see why your not getting a picture. Is your power supply making 12 & 24v? You need to have the power supply pluged into the TV and turn it on to get the 24v side to turn on.
01-14-12 08:53 PM
colonelget
Re: The Magnavox 42mf337b LCD repair thread

I hate to bump an old thread but I was just wondering if anyone was ever to find a solution to this problem. I'm having the same "chirp" issue. I'm an electronics novice. I can test some components with a meter and solder but that about it. I ordered a "repair kit" for the board off ebay it came with replacement caps for C953 C952 C951 and C955. It also had 2 replacement diodes for ZD902 and ZD904. I replaced all the components but i still have the chirp and no picture.
11-15-11 03:06 PM
jeffescortlx
Re: The Magnavox 42mf337b LCD repair thread

You might see more then 12v at that cap, I think there is a voltage regulator after that, that will bring it to 12 volts. So dont be surpriesed if you see 15volts or so.
11-15-11 03:00 PM
RetreatWI
Re: The Magnavox 42mf337b LCD repair thread

I don't have much experience troubleshooting, and those step by step instructions are exactly what I need.
11-15-11 02:53 PM
jeffescortlx
Re: The Magnavox 42mf337b LCD repair thread

I would'nt worry about the rest of the TV just yet. I did'nt have any problems with any thing else, besides the power supply.
The power supply was full of problems for me, capXon cap's, failed MOSFET, failed diodes and a noisy transformer.

Keep on trouble shooting the PSU.
Remove it from the TV, flip it upside down on your work bench, plug in the AC cord and put your volt meter on the single cap that's by it's self. You should see 12 volts. If not, check the large high voltage cap, you should see 200+ DC volts there. If you dont see the high voltage, then you have a problem with the bridge rectifier or the fuse (or other traces) are blown.

Use common sence when doing this. Dont let the board short out on any thing, and dont touch any thing.
11-15-11 02:45 PM
RetreatWI
Re: The Magnavox 42mf337b LCD repair thread

I didn't think it was the problem either. I replaced all 4 of those caps. I'm going to check caps in other boards to see if any are visibly bad.
11-15-11 02:37 PM
jeffescortlx
Re: The Magnavox 42mf337b LCD repair thread

Quote:
RetreatWI wrote: View Post
Could this be the problem? This is from the Philips/Magnovox web site

"By pressing the POWER button on the side of the TV, the mode will toggle from OFF to either STANDBY or ON. If the POWER button is pressed and then the LED on the bezel is red, the TV is in STANDBY mode and will need to be turned on using the remote control. If the POWER button is pressed and then the LED on the bezel is green, the TV is ON."
Naw, I dont think this is the problem. I've noticed with mine some times the light is red, and some times the light is off, depending on if the sleep timer was set or just shut off. But it still allways turns on from the front panel button no matter what.

You see the 3 electrolytic caps grouped together? Thats the 24v switched section. The electrolytic cap across from them by it's self is the 12v constant output (it's a 35v cap IIRC). The 24v output will only fire up when plugged into the TV and the TV sends the signal to turn on. The 12v output is allways on as long as there is a 120v line cord plug into it. If the cap say's 200+ what ever volts, then your in the wrong part of the power supply.
11-13-11 07:00 PM
RetreatWI
Re: The Magnavox 42mf337b LCD repair thread

Could this be the problem? This is from the Philips/Magnovox web site

"By pressing the POWER button on the side of the TV, the mode will toggle from OFF to either STANDBY or ON. If the POWER button is pressed and then the LED on the bezel is red, the TV is in STANDBY mode and will need to be turned on using the remote control. If the POWER button is pressed and then the LED on the bezel is green, the TV is ON."
This thread has more than 10 replies. Click here to review the whole thread.

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