westinghouse LVM-47w1

[multimeter]

Re: westinghouse LVM-47w1

it stays lit probably about 3-5 seconds, im 90% sure its this cap that is buzzing (almost sounds like a cricket) right after the lights go out, when i disconnect the inverters from the power board and power on it doesnt make that noise, so with my logic either the boards are causing it to make the noise or the noise is causing the boards to turn off

on that capacitor you have highlighted on the solder side,either the light is weird,or those are ring cracks around those pins,can you check and reflow those if they are,it could be the arcing sound your hearing

[smai]

Re: westinghouse LVM-47w1

there could be a a boarder line resistance short happening ,can you do a resistance test to ground on the +rails on the inverters?,you should see lots of of kohms,if there is a few ohms,that could indicate a short somewhere,and will have to check the transformer drivers for shorts,passives etc

a short would filter back through the feedback circuits ,and cause some reverse voltage,and that may be the sound your hearing from that capacitor under more load,and the mainboard shuts the psu down and so on

you lost me on this one, where are the +rails? if it is the black circles then with the meter set on 20M they all are about .32 except a few were 3.89 on 200M they all are about 1.1-1.3

i think it is the picture but will reflow anyway

[multimeter]

Re: westinghouse LVM-47w1

no not those,i mean the on the inverter,you have all the connectors from the psu/mainboard bringing in the voltages to the inverter yes?,

well those would be your +rails to check for low ohms to ground,in other words there maybe a low ohm short there that is shutting of the psu etc.

if the inverter isnt happy it will send back a signal through the feedback circuits,and that will tell the psu to shutdown.

[smai]

Re: westinghouse LVM-47w1

okay with the plug disconnected ohm meter set to 200M
master board
VBL 1.3
VBL 1.3
VBL 1.3
VBL 1.3
VBL 1.3
GND 1.0
GND 1.0
GND 1.0
GND 1.0
GND 1.0
VSEL 2.0
E_PWN 2.0
L_PWN 2.0
BL_ON 1.6

Slave board
VBL 2.2
VBL 2.2
VBL 2.2
VBL 2.2
VBL 2.2
GND 1.0
GND 1.0
GND 1.0
GND 1.0
GND 1.0
NC open
NC open

VBL is where the 24V are coming in from the power board, VSEL down is connected tot he main board

i just checked them again the master VBL are all 1.1 and the salves are 1.6

[multimeter]

Re: westinghouse LVM-47w1

okay with the plug disconnected ohm meter set to 200M
master board
VBL 1.3
VBL 1.3
VBL 1.3
VBL 1.3
VBL 1.3
GND 1.0
GND 1.0
GND 1.0
GND 1.0
GND 1.0
VSEL 2.0
E_PWN 2.0
L_PWN 2.0
BL_ON 1.6

Slave board
VBL 2.2
VBL 2.2
VBL 2.2
VBL 2.2
VBL 2.2
GND 1.0
GND 1.0
GND 1.0
GND 1.0
GND 1.0
NC open
NC open

VBL is where the 24V are coming in from the power board, VSEL down is connected tot he main board

and thats megaohm yeah?

[smai]

Re: westinghouse LVM-47w1

i just checked them again the master VBL are all 1.1 and the salves are 1.6

yea the meter is set to 200M

[multimeter]

Re: westinghouse LVM-47w1

those readings dont indicate a short then...going to have a read back through thread again

[multimeter]

Re: westinghouse LVM-47w1

have you re-solderd the inverter transformers,and what looked like cold joints on that capacitor in earlier post?

[smai]

Re: westinghouse LVM-47w1

i didnt resolder the transformers, but i did do the cap

[multimeter]

Re: westinghouse LVM-47w1

do the transformers,they can suffer with cold joints too

[smai]

Re: westinghouse LVM-47w1

should i just grab a heat gun and reflow the whole pcb and inverter boards ?

[multimeter]

Re: westinghouse LVM-47w1

not really ,could do more damage then good without the right gear

hand-draulic im afraid...

[smai]

Re: westinghouse LVM-47w1

when i was talking the board off i thought i would try powering it on with the bulbs disconnected interesting result

on the slave side when any of the bottom 4 bulbs are connected the cap makes that noise with everything else is connected and those 4 are unplugged no noise, the backlight still shuts off in any situation

[multimeter]

Re: westinghouse LVM-47w1

so it could be tube failiure then,do you have a spare set of good ones and plug those in?they would definatley cause your symptoms

[smai]

Re: westinghouse LVM-47w1

no spares, since this monitor has 2 inverter boards would it have 12 tubes or 24? i can move a tube to another spot and see if the problem moves with it right ? where would i even get a new tube ?

or cani i move he inverter board down and plug the bulbs into a different plug and see if the problem is still there

[multimeter]

Re: westinghouse LVM-47w1

could be either 12 or 24,moving a tube to a different position wont make any difference,if there is a bad tube,the feedback circuits will know and shut down.

i keep tubes from tv's for testing stuff like this,makes it easier if you do a lot of tv repairs.

[smai]

Re: westinghouse LVM-47w1

could be either 12 or 24,moving a tube to a different position wont make any difference,if there is a bad tube,the feedback circuits will know and shut down.

i keep tubes from tv's for testing stuff like this,makes it easier if you do a lot of tv repairs.

right but that will tell me if the tube is bad or the board is bad

so if i plug number 9 into the 8th spot (no noise with 8) and i get the noise that will tell me the tube is bad right ? if i dont get the noise then something on the inverter board is bad right ?

[smai]

Re: westinghouse LVM-47w1

new symptom

there is a ribbon connected to the top and bottom of the board when i disconnect the bottom one it will power on like theres nothing wrong although in not sure all bulbs are on and the monitor is a little noisy, bad tubes ?

[multimeter]

Re: westinghouse LVM-47w1

if they are starting to fail they will draw more current,which is overloading everything,it mite work what your asking.

if you had a spare one,you could swap one at a time,until the inverter stays on

[smai]

Re: westinghouse LVM-47w1

is there any way to test the bulb? would i need 160 DCV straight to the tube ?