Riddled TV Repair Forum
Service Menu and Manual Schematics
 
   
 FAQFAQ   SearchSearch   RegisterRegister 
   Log inLog in 
rca M50WH74S   Goto page 1, 2  Next  
Post new topic   Reply to topic    Riddled TV Repair Forum Index -> TV Repair
 
Author Message
mariusz



Joined: 30 Nov 2008
Posts: 12

PostPosted: Sun Nov 30, 2008 11:29 am    Post subject: rca M50WH74S Reply with quote

the chassis #is ATC351A When I pluge the tv in and press the power button it acts like it comes on and then the blue power light on the front blinks 5 times,the light on the power board comes on and the fan inside is on.I have looked at the lamp but it looks ok,I cannot seem to find much about this model of tv.I have read posts about other rca tv's and alot of info points to the flyback transformer,but I cannot find one for this model.The tv has no sound and no picture,and it sounds like it is clicking on the power board.It looks like two of the capacitors 200v 390uf 85C have a slight bulg to them,and the other one is flat.
Google

PostPost subject: Advertisement

Jesse Mack



Joined: 22 May 2008
Posts: 600
Location: The Last Frontier

PostPosted: Mon Dec 01, 2008 11:42 am    Post subject: Reply with quote

No offense, but is seems you have little knowledge about this technology so I will try to explain what is going on.

1: This set has no flyback, that technology is fading fast.
2: If you read your owners manual, it explains that if you have the lamp door off, the front power LED will blink 5 times or if your lamp is bad it will blink 5 times.
3: If you have removed the back, you have to manually restrain the lamp door switch or you will just get the 5 blink symptom.
4: Now, if you are hearing the "clicking sound" that is most likely the spark gap trying to fire the lamp.
5: If you have removed the lamp, observe the direction that the wires go that the lamp plugs into. Do this with the set unplugged.
6: After you find the board that the large wires go to, use a flashlight to find a 1/4 inch diameter 3/8 inch long white device with a bare wire coming out if each end going through the circuit board.
7: Reassemble the lamp and restrain the lamp switch in the on position and plug the unit in.
8: Observe, do not touch anything, the device I described earlier.
9: Do not touch anything (There is 14,000 volts present if the ballast is working.)
10: If, when you turn the set on the white device described earlier lights up momentarily and the lamp does not fire, replace the lamp.
11: If, when you turn the set on and the device does not momentarily fire (light) you may have a bad ballast but I will wait until you have the answer before proceding. Note: the device will light up everytime you hear the clicking sound.
12: Again, do not touch while set is plugged in.

Hope this helps

Jesse
mariusz



Joined: 30 Nov 2008
Posts: 12

PostPosted: Mon Dec 01, 2008 7:33 pm    Post subject: Reply with quote

thank you Jesse for the reply,And no I have little knowledge about the flyback's but I new I could not find anything in the set that looked like all the fly's I seen on the net.The device you describe I have done this and it does light up,and so I will order a lamp.I have a little experience,I fixed a hitachi ultra vision by soldering in the two convergence chips.Thank you very much,I just wanted to make sure before I bought alot of stuff I did not need,because this tv was given to me and the guy told me It had been fixed before and he did not want to spend anymore on it.
theharddrive



Joined: 25 May 2011
Posts: 7
Location: Orange

PostPosted: Wed May 25, 2011 11:28 am    Post subject: Same Television different issue Reply with quote

Hello,

I am working on this same television, but I am having a different issue. The television will come on for a short period generally ranging between 3-30 seconds before it shuts itself off.

I have removed the back and removed the entire light engine assembly.

Once removed I secured the lamp housing safety switch and plugged in the tv. Everything seems OK. I turn the power to the television on now, and everything comes on like it should. The lamp lights up. I can see the color wheel spinning. And I can see the picture being displayed. (performed this step once with the bulb not actually inserted in next to the color wheel so I could see if it was spinning or not)

This all leads me to believe the issue is the power supply. I removed the power supply and closely examined it and on the bottom side there appears to be two chips that are blown. I'm not 100% sure if the little chips can blow, but these two chips have a line of a dark looking goo stretching an inch or so from the chip on the board.

I know what flux looks like and it is not flux so I assume the chip has exploded.

Any suggestions would be greatly appreciated
slinteriors



Joined: 05 Apr 2009
Posts: 32
Location: North Carolina

PostPosted: Wed Jun 01, 2011 9:49 am    Post subject: Reply with quote

Whats the board location numbers of the items your refereing too? Let me know and I will let you know what they are.
Google

PostPost subject: Advertisement

theharddrive



Joined: 25 May 2011
Posts: 7
Location: Orange

PostPosted: Wed Jun 01, 2011 1:23 pm    Post subject: Board Location #s Reply with quote

The board location #'s are IC809 & D828.
slinteriors



Joined: 05 Apr 2009
Posts: 32
Location: North Carolina

PostPosted: Wed Jun 01, 2011 1:40 pm    Post subject: Reply with quote

D828 is a SMD Diode STPS3L40U RCA part number 273946. IC 809 is a IC L5973D switch RCA part number 273956 If you need further assistance let me know.
theharddrive



Joined: 25 May 2011
Posts: 7
Location: Orange

PostPosted: Wed Jul 13, 2011 9:36 am    Post subject: Q Reply with quote

So I ended up just ordering another board as I could not find one of the chips.

The board I received had the EXACT same chips with a goo looking like it blew out the side of the chip. The people insist to me that it is just glue.

Here is a picture of the board I received. Is this just glue as they are telling me?

http://i1206.photobucket.com/albums/bb455/theharddrive/IMG_20110712_133659.jpg
slinteriors



Joined: 05 Apr 2009
Posts: 32
Location: North Carolina

PostPosted: Wed Jul 13, 2011 10:24 am    Post subject: Reply with quote

Is it identical to your board? I have never seen glue such as that but have see silicon used in high stress areas, But have never seen anything even remotely like that for a surface mount.
theharddrive



Joined: 25 May 2011
Posts: 7
Location: Orange

PostPosted: Wed Jul 13, 2011 10:26 am    Post subject: Board Reply with quote

Yes, it was an identical board. Of course the spray from the goo was slightly different, but other than that exact same board.

I was thinking the same thing. I have seen lots of boards out of a lot of different units, but I have never seen anything that even closely resembles this.
Display posts from previous:   
Post new topic   Reply to topic    Riddled TV Repair Forum Index -> TV Repair All times are GMT - 6 Hours
Goto page 1, 2  Next
Page 1 of 2

 


Disclaimer: All information provided by RiddledTV is strictly for information purposes only. Please observe all warnings displayed on your electronic
devices. This information should only be used to help diagnose work, and all service should be performed by a qualified technician.
Contact Us       Privacy Policy       Copyright © 2015 RiddledTV.com       Advertise on RiddedTV.com