Insignia NS-LCD32-09 with power on/off issues

[waitery]

Have an Insignia NS-LCD32-09 with power issues, meaning that it turns itself on and off by itself at will. I took the back of the set off and measured the standby voltage on the power board, which should be at 5volts and it's anywhere from 4.95 to 4.99 volts. I am thinking that it is touching the threshold voltage and turning itself on and off. Power board model number is 715T2804-1.

Caps all "look" good and there are no visable issues with other components, burn/scorch marks, etc.

Any thoughts or ideas on what I can do for next steps?

[multimeter]

Re: Insignia NS-LCD32-09 with power on/off issues

try unplugging the tv buttons from main board,could be sticky tactile switches and see how it goes,could also be a dry joint,the 4.95 to 4.99 volts is fine,most are never spot on what the voltage legends say

[waitery]

Re: Insignia NS-LCD32-09 with power on/off issues

try unplugging the tv buttons from main board,could be sticky tactile switches and see how it goes,could also be a dry joint,the 4.95 to 4.99 volts is fine,most are never spot on what the voltage legends say

Thanks MM, I tried exactly that, thinking that the side board was not working properly, but no effect. It just seems to power on when it gets warm and then powers itself off and then cycles again.

[multimeter]

Re: Insignia NS-LCD32-09 with power on/off issues

Thanks MM, I tried exactly that, thinking that the side board was not working properly, but no effect. It just seems to power on when it gets warm and then powers itself off and then cycles again.

how long before it shuts off when tv is on?
it could also be a capacitor issue,try heating the psu with hot air around the output caps,and see if it stays on longer.

you have the standby voltage that goes to the on signal,does the on signal voltage drop off when the fault occurs?

[waitery]

Re: Insignia NS-LCD32-09 with power on/off issues

how long before it shuts off when tv is on?
it could also be a capacitor issue,try heating the psu with hot air around the output caps,and see if it stays on longer.

you have the standby voltage that goes to the on signal,does the on signal voltage drop off when the fault occurs?

It seems to cut in and out at like 5-7 minute intervals. I pulled the output caps that feed the 5V line, thinking I had a high ESR issue or a lowered capacitance issue, but all three caps were good all the way around (ESR and Capacitance were both better that the nominal values).

When I put my meter on the 5volt STB line and the tv swithes on by itself, the voltage dips to 4.93 volts and then comes back up to 4.98-4.99 volts, but I have never seen it go to 5 volts at any time.

[tom66]

Re: Insignia NS-LCD32-09 with power on/off issues

What about the other rails?

[crashp3]

Re: Insignia NS-LCD32-09 with power on/off issues

Sent the SM to tom66 for this set... I'm sure it'll be posted to his site soon

[waitery]

Re: Insignia NS-LCD32-09 with power on/off issues

What about the other rails?

Hi Tom, the other rails check out perfectly. 24.2 volts and 12.15 volts and everything is steady. No problems there, it's just this low standby voltage that is under 5 volts.

[tom66]

Re: Insignia NS-LCD32-09 with power on/off issues

It's up

[budm]

Re: Insignia NS-LCD32-09 with power on/off issues

When it goes off, see if the 12V and 24V go away, these two voltages are turn on by the PS_ON signal as shown in the diagram. See if the PS_ON also goes away. See page 52 of the service manual.
Please note that there is error on how CN902 is labeled and connected on page52. See page 50 at CN701 for correct pin out.

[waitery]

Re: Insignia NS-LCD32-09 with power on/off issues

It's up

Thanks so much, guys! To be honest, it's been a while since I looked at a schematic. So both caps in the 5 volt line are good, as I have pulled and tested them on an ESR meter. What are the logical next steps to follow?

[tom66]

Re: Insignia NS-LCD32-09 with power on/off issues

I think the standby voltage is fine, but can you check the 24V on the power board or the inverters? If you need help, post a picture of the power board and the test point can be highlighted.

[waitery]

Re: Insignia NS-LCD32-09 with power on/off issues

I think the standby voltage is fine, but can you check the 24V on the power board or the inverters? If you need help, post a picture of the power board and the test point can be highlighted.

Yes, you bet. I will post a picture shortly.

[waitery]

Re: Insignia NS-LCD32-09 with power on/off issues

Yes, you bet. I will post a picture shortly.

Here is a pic of the power board.

[budm]

Re: Insignia NS-LCD32-09 with power on/off issues

Please post the pictures using advanced/attachment function, posting in-line pictures will cause the page to load up real slow. Thanks.

[waitery]

Re: Insignia NS-LCD32-09 with power on/off issues

Please post the pictures using advanced/attachment function, posting in-line pictures will cause the page to load up real slow. Thanks.

Bud, I used the attachment tool to attach this pic.

Also, I checked the PS_ON, per the schematic. When the unit turns itself off, the voltage drops off for PS_ON pinout as well. It falls to .059 volts and is steady. Let me know what's next.

[budm]

Re: Insignia NS-LCD32-09 with power on/off issues

since your 5V power supply is OK, and the PS_ON goes away, then it points the problem to be on the main board. You will have to start checking the voltage regulators and solder joints and connections next.
We will need pictures of the main board next.

[waitery]

Re: Insignia NS-LCD32-09 with power on/off issues

since your 5V power supply is OK, and the PS_ON goes away, then it points the problem to be on the main board. You will have start checking the voltage regulators and solder joints and connections next.
We will need pictures of the main board next.

Hey Bud, I just went through all the FETs on the main board and retouched them with solder. We seem to be up and running again and the on off switch is running. I will burn test it for 24 hours and see if it fails. I will let you know.

[budm]

Re: Insignia NS-LCD32-09 with power on/off issues

Well, may be you are getting some where, I hope you have really good magnifying glass to really check all the joints on the board. Crossing fingers!

[budm]

Re: Insignia NS-LCD32-09 with power on/off issues

Still working?