The Magnavox 42mf337b LCD repair thread - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

Reply
 
Thread Tools
post #11 of 28 Old 08-24-11, 02:52 PM Thread Starter
Shackster
Jeff
 
Join Date: Aug 2009
Location: Minnesota
Posts: 84
Re: The Magnavox 42mf337b LCD repair thread

After installing a new set of P6KE120A diodes, TV powers up again and works.
It's quite untill it's running for awhile then the sqeal sound starts up again.

I went ahead and installed new 1500uf & 2200uf caps, the capXon ones that were in there did'nt fail, but I did'nt trust them.

In the 2nd picture, you can see the diodes are raised up off the board now. So if they fail again, and least it wont burn a hole in the board.
Attached Thumbnails
The Magnavox 42mf337b LCD repair thread-power-supply.jpg  

The Magnavox 42mf337b LCD repair thread-power-supply-2.jpg  


Last edited by jeffescortlx; 10-02-11 at 10:15 AM.
jeffescortlx is offline  
Sponsored Links
Advertisement
 
post #12 of 28 Old 09-14-11, 09:17 PM Thread Starter
Shackster
Jeff
 
Join Date: Aug 2009
Location: Minnesota
Posts: 84
Re: The Magnavox 42mf337b LCD repair thread

Now I have a 37MF231D/37 37" LCD Mag/Philips in with problems.
The owner is claiming they hear a squel sound, and it will power it's self off some times.
I have the power suppy out, and it looks like this should be a more clear cut and dry fix.
Cap # 2074 (2200uf 25v) & cap # 2081 ( 1200uf 35v) is buldged out with stuff poping out the top. All electrolitics are CapXon Brand.

Order notes for me self:
# 2081 31mm x 12.5mm
# 2074 26mm x 12.5mm
Good caps:
# 2080 & 2082 25mm x 12.5mm 1000uf 35v
^All 105º with 5mm lead spacing, radial lead.
# 2062 32mm x 30mm 180uf 450v
^10mm lead spacing.
And the cermatic cap that makes the noise off the zenar diodes is # 2063 B 152

Last edited by jeffescortlx; 09-15-11 at 03:20 PM.
jeffescortlx is offline  
post #13 of 28 Old 11-13-11, 09:08 AM
Shackster
 
Join Date: Feb 2011
Location: Acworth, GA
Posts: 10
Re: The Magnavox 42mf337b LCD repair thread

I picked on of these up at the Goodwill that wasn't working. I just replaced the 3 large capacitors, 1 large capacitor, the 2 diodes, and the Mofset. I also put in a new fuse and it still won't power on. Any other suggestions?

Thanks
RetreatWI is offline  
 
post #14 of 28 Old 11-13-11, 11:28 AM Thread Starter
Shackster
Jeff
 
Join Date: Aug 2009
Location: Minnesota
Posts: 84
Re: The Magnavox 42mf337b LCD repair thread

Quote:
RetreatWI wrote: View Post
I picked on of these up at the Goodwill that wasn't working. I just replaced the 3 large capacitors, 1 large capacitor, the 2 diodes, and the Mofset. I also put in a new fuse and it still won't power on. Any other suggestions?

Thanks
Does the constat 12v section of the power supply work?
I ended up just gutting the 24v section and adding a meanwell 350watt power supply.
jeffescortlx is offline  
post #15 of 28 Old 11-13-11, 05:03 PM
Shackster
 
Join Date: Feb 2011
Location: Acworth, GA
Posts: 10
Re: The Magnavox 42mf337b LCD repair thread

I don't have any idea. I am not very well versed in electrical diagnosing. I can desolder and solder. That's about it.
RetreatWI is offline  
post #16 of 28 Old 11-13-11, 05:39 PM Thread Starter
Shackster
Jeff
 
Join Date: Aug 2009
Location: Minnesota
Posts: 84
Re: The Magnavox 42mf337b LCD repair thread

Power it up and check the 12v side. It does'nt need to be connected to the TV for the 12volt section.
Any of the cap's buldged?
jeffescortlx is offline  
post #17 of 28 Old 11-13-11, 05:59 PM
Shackster
 
Join Date: Feb 2011
Location: Acworth, GA
Posts: 10
Re: The Magnavox 42mf337b LCD repair thread

None of the caps were bulged. When you say "power it up and check the 12v side", can you give me instructions on what and where how to check it? Thanks
RetreatWI is offline  
post #18 of 28 Old 11-13-11, 06:55 PM
Plain ole user
 
lcaillo's Avatar
Tech Guru
 
Join Date: May 2006
Location: Gainesville, FL, USA
Posts: 11,121
Send a message via AIM to lcaillo
Re: The Magnavox 42mf337b LCD repair thread

If the connectors or test points are not labled you will need a schematic to be sure where the 12v comes out of the supply.




Looking for me, just google my username. I have used the same one for most sites for many years.
lcaillo is offline  
post #19 of 28 Old 11-13-11, 07:00 PM
Shackster
 
Join Date: Feb 2011
Location: Acworth, GA
Posts: 10
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."

Last edited by RetreatWI; 11-13-11 at 08:09 PM.
RetreatWI is offline  
post #20 of 28 Old 11-15-11, 02:37 PM Thread Starter
Shackster
Jeff
 
Join Date: Aug 2009
Location: Minnesota
Posts: 84
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.
jeffescortlx is offline  
Reply

Bookmarks

Tags
42mf337b , magnavox , repair , thread

Quick Reply
Message:
Options

Register Now




PLEASE COMPLETE ALL REQUIRED FIELDS BELOW... THANKS!

REQUIRED FIELDS ON THIS PAGE
YOU MUST COMPLETE ALL OF THESE

Username
Password
Confirm Password
Email Address
Confirm Email Address
Random Question
Random Question #2




User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
PLEASE READ BELOW PRIOR TO ENTERING AN EMAIL ADDRESS!

ATTENTION!

YOU MUST ACTIVATE YOUR ACCOUNT!

Activation requires you reply to an email we will send you after you register... if you do not reply to this email, you will not be able to view certain areas of the forum or certain images... nor will you be able download software.

AN INVALID EMAIL ADDRESS WILL CAUSE YOUR ACCOUNT TO BE DELETED!

See our banned email list here: Banned Email List

We DO NOT respond to spamcop, boxtrapper and spamblocker emails... please add @hometheatershack DOT com to your whitelist prior to registering or you will get nowhere on your registration.


Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML is not allowed!
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 


For the best viewing experience please update your browser to Google Chrome