Emerson hdtv troubleshooting

[ddarn]

Ok,since my Dynex is in the process of being troubleshot,I will go ahead and start this new thread for my Emerson.I had electrical strike that I believe either came in on the power line and/or via the satellite coaxial cable.
It is an Emerson LC320EMZ.....I am attaching the power board pictures of the front and back.I apologize if the images are hard to view because I am using a camera phone under a house light.Thanks for your help!

[selldoor]

Re: Emerson hdtv troubleshooting

given that the tests for a lightning strike/power surge will be the same for
most tvs why not parallel the tests and just tell us the results?

As you say the pictures are almost useless for troubleshooting.

[martino]

Re: Emerson hdtv troubleshooting

You can take some info from your other thread as in to start measuring some points..
Powerboard disconnected from everything else,plugged in,meaurement across that large cap in the HOT section,meter on DC high voltage as you can expect up to 400 volts(167 in standby).
Is there anything printed by the cable going to the mainboard? Looking for the standby voltage..
Is there a board number on the powersupply? (then we can find a schematic)

[ddarn]

Re: Emerson hdtv troubleshooting

its reading 48.2 mV.......off the sticker on the board:120820p19a a17ft-mpw p/o:e7226690
L:11072-03277......at another spot its got ba17f1f0102 5. this one looks like its going to be more difficult to spot..would you like me to take a better picture of the front and back of the board?

[martino]

Re: Emerson hdtv troubleshooting

yes a good close up of the HOT side of the board(around where it plugs 110v in and the big cap etc..)
48mv on the main cap? meter was on DC voltage ?
I think we need to trouble shoot this one even before the main filter cap,lets wait for the pictures...I will try and dig up a schematic..

[ddarn]

Re: Emerson hdtv troubleshooting

Yes in DC...pics to come..

[selldoor]

Re: Emerson hdtv troubleshooting

Tested the fuse?

If that is ok there are 4 diodes just above where it says cold on the right hand side of the board in your picture. Can you test those.

[ecking767]

Re: Emerson hdtv troubleshooting

check the main board, and post pictures of the main board.

[ddarn]

Re: Emerson hdtv troubleshooting

power board pics of the hot area...fuse was good.

[selldoor]

Re: Emerson hdtv troubleshooting

Ok like I said you need to test the 4 diodes top right in those last pictures

and also the 2 white boxes are inrush resistors - check them for continuity.

Neither test requires power to the board

[martino]

Re: Emerson hdtv troubleshooting

see pic...

Check #1 as you would check a fuse...TV UNPLUGGED!!!!
#2 are 4 diodes(as suggested earlier by selldoor),TV UNPLUGGED!!!.
Put meter on diode scale,measure each diode from the one leg to the other leg.then reverse your probes and test again...

http://www.youtube.com/watch?v=qSDRsz5-t7I

[ddarn]

Re: Emerson hdtv troubleshooting

what is #1? ...I checked the 4 diodes top to bottom ,left to right as seen in the pic..readings are as follows 1-4.55m ohms/(reverse leads-open)..2-4.27 M (rev-open)...3--4.13M(rev--open).....4- 4.39 M (rev-open).... both resistors 1.3 ohms.My meter doesnt have a different diode setting..it is placed with my ohm setting.

[martino]

Re: Emerson hdtv troubleshooting

I forgot to add pic...

[budm]

Re: Emerson hdtv troubleshooting

"power board pics of the hot area...fuse was good." What do mean by WAS GOOD? Is it still good? There is not much in the rectifier circuit, the 4 Diode are set up as a bridge, the Cathode of two Diodes (D601, D602) are tied together, then it is connected to those tow white fusible resistors (R602, R611), the output side of the resistors are connected to the + of the main filter cap, the Anode of the other two diodes (D600, D603)are tied together and then are connected to the - of the cap. So there must be an error in reading some where.
These are better pictures provided by Shopjimmy.
See how the main filter cap is charged up to 170VDC.
You should also check and see if the Surge Arrestor SA601 is not shorted due to the surge.

[martino]

Re: Emerson hdtv troubleshooting

I'm wondering if the 110 ac even makes it to the bridge.

[budm]

Re: Emerson hdtv troubleshooting

He should test for AC right at the L and N as I marked them,or if the fuse is blown (he said it WAS GOOD) or those two AC line filter inductors are also blown open. There is not much to the circuit, he should be able to do resistance test from the Line and Neutral terminals all the way to the diodes. see post 14 drawing.
It is hard to do long distance troubleshooting if the information are not correct.

[martino]

Re: Emerson hdtv troubleshooting

I was wrong too,in post #13 I circled part#1(Surge Arrestor SA601),thinking it was in series with the 110 line..
Now looking at your #14 pic drawing its parallel...

[ddarn]

Re: Emerson hdtv troubleshooting

I forgot to add pic...

1 is 1.19 m ohms

[selldoor]

Re: Emerson hdtv troubleshooting

Ok -see the plan budm drew for you. Locate on the bottom of the board
where the mains lead pins are and where the BIG cap pins are.

Working on a non conductive surface have just that board with the bottom
face up. Set your meter on VAC 600 and with the board plugged into the main test the voltage on the two mains lead joints. CAREFULLY.

Next change your meter to 600vDC ( I cant remember is yours an allranging one? ) anyway with it on 600v DC test the voltage across the BIG Cap joints Again CAREFULLY

[ddarn]

Re: Emerson hdtv troubleshooting

oops forgot to have the board plugged in when I checked the big cap ....so I will be starting the readings over ...the big cap reads 160.8 vdc with power, vac is overlimit..