Insignia NS-L26Q-10A no power

[BurghMan]

----Summary----
My Insignia NS-L26Q-10A TV will not turn on. The front LED never turns on.


----Things Tested----
1) The power supply (715G3418-P01-000-003M) produces 5VDC, but there is never 12VDC or 24VDC produced.
2) I tried to replace the mother board (715G3239-M02-000-005F) with a similar mother board (715G3239-1-1). The connection to the LCD is different, so I didn't connect the LCD, but everything else is the same. When I pressed the power button with this mother board in nothing happened.
3) Nothing on the boards looks damaged.
4) I checked to make sure the power button (on/off switch) is switching properly. I performed a connectivity check and was able to see the connections being made and disconnected when the power button was pressed.
5) The voltage going to the power button is .5VDC.

----Question----
Is the mother board bad? Why won't the 715G3239-1-1 mother board work? Is there anything on the mother board I should be checking?

[vinceroger69]

Re: Insignia NS-L26Q-10A no power

can you post good pictures of the two top connectors on the psu so we can see what the printing is by the connectors may be we can use a resistor to test the psu outputs.

[BurghMan]

Re: Insignia NS-L26Q-10A no power

The 2 connectors on the power supply are pictured below. The connections are labeled as follows….

Connector to the Mother Board (top to bottom):
On/Off
PDIM
+12
+12
GND
GND
+24
+24
PS_ON
+5V
+5V

Connector to 715G3631-P02-000-003S - I'm not sure what this board is:
VS
IS1
GNS
IS2

[vinceroger69]

Re: Insignia NS-L26Q-10A no power

have you got your original man board in the set so we can start trouble shooting from the start?

[BurghMan]

Re: Insignia NS-L26Q-10A no power

Yes all original boards are in.

[selldoor]

Re: Insignia NS-L26Q-10A no power

Its getting late here but you need to try and find a 1k or 0.5kohm resistor.
If no one chimes in also look for fuses - the main one must be ok as you have 5v but there may be others (pics are a bit small) should be labelled F??? and could even be on the back of the board.

[budm]

Re: Insignia NS-L26Q-10A no power

"Connector to the Mother Board (top to bottom):
On/Off
PDIM
+12
+12
GND
GND
+24
+24
PS_ON
+5V
+5V"

Report the DC voltage readings on all those pins when TV is OFF, and when power switch is activated. Black probe of the meter on the chasssis.

[BurghMan]

Re: Insignia NS-L26Q-10A no power

I have a 1kohm resistor and I did not find any other fuses besides the main fuse on the Power Supply board, which has been checked and is not blown.

I tested the voltages of each pin with the black probe on the chassis. Here are the readings I got, they were the exact same when the power button was pressed in:
On/Off = OVDC
PDIM = -0.1VDC
+12 = 0.002VDC
+12 = 0.002VDC
GND = 0VDC
GND = 0VDC
+24 = 0VDC
+24 = 0VDC
PS_ON = 0.412VDC
+5V = 5.017VDC
+5V = 5.017VDC

[selldoor]

Re: Insignia NS-L26Q-10A no power

We could do with a bigger picture of the boards and also the back.
but if it is all connected wait and see if budm comes back on later.

I did see some grey looking resistors - these could be fusible resistors and act as fuses
so please check them for continuity as you would a fuse.

[BurghMan]

Re: Insignia NS-L26Q-10A no power

I will work on getting bigger pictures for you of both boards.

I didn't realize the fuses could be as small as the resistors. I started checking everything labeled FBXXX and came across three instances shown on the picture. It looks as if FB205 and FB202 don't have fuses soldered in. When I check for a connection, the meter reads OL (open loop). Should this be a concern or where these fuses intentionally left off?

[multimeter]

Re: Insignia NS-L26Q-10A no power

I will work on getting bigger pictures for you of both boards.

I didn't realize the fuses could be as small as the resistors. I started checking everything labeled FBXXX and came across three instances shown on the picture. It looks as if FB205 and FB202 don't have fuses soldered in. When I check for a connection, the meter reads OL (open loop). Should this be a concern or where these fuses intentionally left off?

"fb" designations will be ferrite beads,should show very low ohm reading or even dead short when tested

[budm]

Re: Insignia NS-L26Q-10A no power

"On/Off = OVDC
PDIM = -0.1VDC
+12 = 0.002VDC
+12 = 0.002VDC
GND = 0VDC
GND = 0VDC
+24 = 0VDC
+24 = 0VDC
PS_ON = 0.412VDC
+5V = 5.017VDC
+5V = 5.017VDC"
The main board is the problem, it is not sending out PS_ON signal.

[BurghMan]

Re: Insignia NS-L26Q-10A no power

Ok, thanks. I'm assuming I must try to find the exact same main board for a replacement, right?

[multimeter]

Re: Insignia NS-L26Q-10A no power

Ok, thanks. I'm assuming I must try to find the exact same main board for a replacement, right?

there still could be stuff that can be fixed on your mainboard,dont give up yet!

caps,voltage regulators...etc

look for your ps_on rail,trace it back,what components are along the line?

what resistance reading do you get if you red probe to ps_on to black probe chassis ground?

[multimeter]

Re: Insignia NS-L26Q-10A no power

these psu's as a note are used in pc monitors too,hmm gonna check me junk pile,or i wont sleep!

[BurghMan]

Re: Insignia NS-L26Q-10A no power

Which PS_ON trace should I be looking at, the one on the Main Power Supply board, or the one on the Mother Board?

[multimeter]

Re: Insignia NS-L26Q-10A no power

Which PS_ON trace should I be looking at, the one on the Main Power Supply board, or the one on the Mother Board?

im thinking problem lies in the main board(motherboard) from what ive read and concluded

check semi's,and passives backwards along ps_on rail for shorts.

but see if you have a short 1st by checking that rail to cold ground(chassis)

[BurghMan]

Re: Insignia NS-L26Q-10A no power

I checked PS_ON to ground and got 2.12kohms. Does this seem right?

I've been trying to trace out this circuit but its very difficult. There are very little visible traces on this board (see pictures), so I've been using my conductivity meter to see what is connected to what, but I don't know what is supposed to be connected to each other.

So far I can see resistors, capacitors, and ferrite beads. It also looks like there are so inductors, diodes, and integrated chips, but I haven't traced the circuit to those elements yet.

[selldoor]

Re: Insignia NS-L26Q-10A no power

There are 2 voltage regulators in your pic u708 is one - perhaps test those and check the voltage on the caps connected to them.

[budm]

Re: Insignia NS-L26Q-10A no power

Beside the main board not sending out the PS_ON signal, it is also not sending out the INV-ON-OFF signal, you have multiple problems on the main board.