insignia NS-L47Q09-10A no sound or picture

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

I will check that today


thanks

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

You get +5v on the mainboard connector, but does the +5v rail get to pin 1, 4 and 7 on U706?

Looking at page 81, U706 gets +5v (via +5VSB) before the other regulators - the other regulators have their +5v (VCC5D) switched through Q703.

You should also check that the +5VSB is getting to all the components in Q703's control circuit.

U706 Pin 1, 4, and 7 are getting 4.97v

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

Q703 pin 1, 2, and 3 get 4.97v

Im not sure how to test the rest of the components in the circuit
For the resistors do I switch the meter to ohms and test both ends with both leads or leave the negative lead on the metal to ground it?

Sorry im a newbie and I haven't gone this far into detail to test these small components

[Agent24]

Re: insignia NS-L47Q09-10A no sound or picture

Yes, to test a resistor put your meter into ohms mode (make sure the device you are checking is OFF first) and connect the probes across the resistors terminals.

However, testing in-circuit may give false readings, you really need to desolder the resistors to test correctly, unless you know there is nothing in parallel with them.


Do you get any voltage on the output of L705? (Opposite side to Pin 10 of U706) - It should be 3.3v

With power off, check the resistance between the output of L705 and ground. What is it?

Sorry im a newbie and I haven't gone this far into detail to test these small components

No worries, we all are at some point

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

Pin 10 of U706 I get 0.455 (2nd picture)

Am I supposed to actually test L705?
Im not sure how to

See the 1st picture am I supposed to place the lead on each of the 4 corners?

1- 0.455
2 - 0.455
3 - 0.397
4 - 0.397

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

How do I check resistance between the output of L705?

Do I put my meter on ohms and check each corner of L705?

[Agent24]

Re: insignia NS-L47Q09-10A no sound or picture

If you wanted to test L705 you would need inductor meter\ring tester but it's probably OK.

It has 4 physical pins but electrically only two pins and thus you have two pairs of pins and each pair will be connected together. From your voltage measurements Pins 1 & 2 are one pair, pins 3 & 4 are the other (since those have the same voltage\same point in the circuit)

I assume you measured each of L705's pins with respect to ground? If so, I would say check on Ohms range between L705 Pin3\4 and Ground. It could be that you have a short or leaky component somewhere on your 3.3vSB rail, since U706 is getting power but not outputting the 3.3v that it should be.

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

Hopefully I did this right

With the red lead on L705 and the black lead on the ground screw
These are the ohm readings with power off

1 - 0.8
2 - 0.8
3 - 0.7
4 - 0.7

[Agent24]

Re: insignia NS-L47Q09-10A no sound or picture

Well, the good part is you did the measurement correctly.

The bad part is that it would appear then that something on that 3V3_STB rail is shorted, assuming your reading is 0.7 Ohms?

That 3V3_STB rail goes to many places on the board, so finding out where the fault is could be tricky.

I do notice in the schematic that 3V3_STB goes to some off-board connectors, so you might be able to narrow it down by unplugging things from the mainboard.

Otherwise, since power supplies and regulators fail more often, you could try disconnecting the input pin (pin 3) of regulator U702, desoldering the ceramic capacitors C767 and C705 and checking again for shorts. (try after each one) as it is a bit more likely to be one of those three items.

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

Yes it is in ohms
So if I understood you correctly

Desolder pin 3 on U702
Then what should I retest?

After that do I resolder pin 3 and desolder the C705 and then retest what components?

And so on with C767?

[Agent24]

Re: insignia NS-L47Q09-10A no sound or picture

Desolder Pin 3 of U702 and again check the resistance between Pin 3\4 of L705 to ground.

First though, disconnect all off-board cables from the mainboard and check resistance between Pin 3\4 of L705 to ground to be sure the fault is on the mainboard and not somewhere else.

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

Ok I disconnected everything from the main board

I got the same ohm readings

1- 0.8
2- 0.8
3- 0.7
4- 0.7 ohms

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

I desoldered pin 3 of U702

I retested pin 1, 2, 3, 4 of L705 and I got the same readings as above

[Agent24]

Re: insignia NS-L47Q09-10A no sound or picture

You could try removing those filtering capacitors, but if it's not them, it could be a variety of things on the motherboard, and may be hard to find.

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

i will remove each capacitor one at a time and check L705

should i resolder pin 3 on U702 or leave it as is after i remove the capacitors?



thanks

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

I will remove the capacitors today

if it turns out not to be these components I will just order a main board

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

Ok so I removed both capacitors

I removed C767 and checked ohms with pin 3 of U702 desoldered
I got the same exact readings as before for U702

Then I removed C705 and same exact readings as before

Im going to order a board from eBay today
Hopefully I get it on Tuesday

[Agent24]

Re: insignia NS-L47Q09-10A no sound or picture

If it is not the supply capacitors and if you have a sensitive enough meter, you may be able to go around the board checking at components that are on that rail, the one with the lowest ohm reading is the shorted part (or a part nearby)

The other option is to supply 3.3v to that rail via a bench supply, and see which component lets out smoke.

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

I dont have a bench supply

[jose6326]

Re: insignia NS-L47Q09-10A no sound or picture

I need help deciding which board to buy

My board is 715G3269-1 (TQ9C8 ZK05201)


The following has the same board number but different bar code number and is missing an hdmi port It was not removed it was manufactured this way

http://www.ebay.com/itm/291165195578...torefresh=true


The following has the same board number but different bar code number but is exactly like the board I have

http://www.ebay.com/itm/261498450350...84.m1423.l2649


I think either one will work