WS48511 no led activity at all from power button, feels like DM issue but different.

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lulsas
WS48511 no led activity at all from power button, feels like DM issue but different.

So I finally decided to fix my old WS48511. I found all the information about the Caps going bad on the DM power module, etc. When I went to check none of the caps were bulging. I used my multimeter to test resistance and every cap increased to infinity. I know this is just a rough , rough indicator they "may" be ok but everything I've read finds people with failures with bulged caps. On a whim I decided to check the power button and it completes the circuit fine. The TV has zero response when the power button is pushed. The power on led does not flash or come on at all. If I use the manual reset, the led will blink for about (havent timed exactly) 30 seconds steady then shut off. A couple of years ago when I was still using it i did have a period when it wouldn't turn on just like now. Out of the blue it started working again and did so until I bought a new tv. Now that it's been sitting for a year or so, it won't turn on again. Looking for some direction, tips, anything otherwise the tv is headed for recycling. 

 

Perhaps I should replace all the caps on the dm power module anyways?

Big Fe
This is a long shot. Try

This is a long shot. Try disconnecting the front panel circuit board cable and then use the remote to turn on the set. I've seen this cure a similar problem with that model.

lulsas
I'll be damned. It worked. I

I'll be damned. It worked. I would love to know the tech answer behind this. I haven't put the tv back together yet, but I was able to see the picture in each projection lense (front is is off atm). Thank You oldtech2.

lulsas
Ok, so I have it back

Ok, so I have it back together. Operates fine with the front panel board disconnected but fails to register any remote control commands with it connected. Since I've tested all the paths on the front panel circuit board I'm assuming the issue is on the main board (inside TV). Anybody have any details on this problem for this model?

EXtek
lulsas said: Ok, so I have it

lulsas said: Ok, so I have it back together. Operates fine with the front panel board disconnected but fails to register any remote control commands with it connected. Since I've tested all the paths on the front panel circuit board I'm assuming the issue is on the main board (inside TV). Anybody have any details on this problem for this model?

He can correct me if I'm wrong, but I dont think oldtech was suggesting that disconnecting the board would actually repair the set. Before assuming there is a fault in the main board I would check the front control board first. It could be simply a failed tact switch fouling up the works.

lulsas
@EXtek: I had the front board

@EXtek: I had the front board out already and I hooked to the negative and tested each button with my multimeter. Each button broke and completed it's circuit properly so I'm not sure at this point. Everything points to a problem on the front panel circuit board but I'll be damned if I can find a short anywhere. I have a fair working knowledge of electrical stuff but am an expert by no means. I'm up for any ideas or theories I can test. Despite my testing the circuit board/buttons and it checking out my gut is telling me it's something in that front circuit board I'm not finding.

EXtek
 

 

lulsas said: @EXtek: I had the front board out already and I hooked to the negative and tested each button with my multimeter. Each button broke and completed it's circuit properly so I'm not sure at this point. Everything points to a problem on the front panel circuit board but I'll be damned if I can find a short anywhere. I have a fair working knowledge of electrical stuff but am an expert by no means. I'm up for any ideas or theories I can test. Despite my testing the circuit board/buttons and it checking out my gut is telling me it's something in that front circuit board I'm not finding.

 

The functions on the front are not actuated by 0 ohms resistance (or dead short) coming from the switches. With the exception of the power switch there is a resistor in each of the switches path. So even if a tact switch is not dead short it could be a case where its not opening up all of the way, or has a high rsistance. This could send a false command to the main board and foul up the works. You may have to go through (one at a time) and desolder switches on one side breaking their connection from the pc board and see if you can operate it normally using the remote. According to the info I have here there should be 10 switches. But before doing any of that, there is a 7.5 volt Zener diode on the board, check it first.

 

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