Insignia NS-50P650A11 - Bad Power Supply?

[tds-1541]

I am attempting to repair an Insignia NS-50P650A11 50" Plasma TV that will not power on. It exhibits the following behavior: Immediately after applying AC to the power supply, the boards two relays click on and after a brief period, the relays click off and this cycle repeats it self every 5 to 10 seconds indefinitely.

I verified that all voltages (Vs, Va, 3.3v, 5v, 15v) appear to be in spec except the 15v rail, which appears to dip down below 11v before the relays disengage. Currently, the high-voltage connector that provides power to the X&Y Sustain is unplugged as is the connector to the LVDS control board. The behavior does not change when this connector is plugged in or unplugged.

Is this indicative of a power supply? The power supply is a Samsung BN44-00330A.

Here is a YouTube video which outlines the behavior: https://www.youtube.com/watch?v=iM6aJCe3HWk

Thanks in advance, TDA-1541.

[capkid]

Re: Insignia NS-50P650A11 - Bad Power Supply?

This may be helpful. Your power supply is most likely ok. The TV in the linked thread ended up being the 42" version, but the information should apply. Be careful with board swapping, as a bad board could end up blowing a good board.

https://www.badcaps.net/forum/showth...t=Ns-50p650a11

[tds-1541]

Re: Insignia NS-50P650A11 - Bad Power Supply?

Hmm, I read that form before posting, but none of the symptoms appeared to match mine. Additionally, no combination of connecting or disconnecting connectors has changed that constant click on and off repeating every 5 seconds other than to disconnect the power supply from the main logic board.

I've tested, in circuit using diode mode on my DMM, every large diode/rectifier and transistor/MOSFET on the power supply and both X&Y sustain units and none show dead shorts. Any other tests that you would recommend to verify the X&Y sustain units?

Any thoughts on that 15v rail sagging to under 11v? The owner of the TV indicated that initially, if they let it click away for a long period of time, it would eventually "warm up" and would display a picture. I never witnessed this behavior for my self, but I did notice that the 15v rail started out in the low 11v range and after a few minutes, it climbed to the high 11v range. Perhaps this is unrelated.

TDA-1541

[capkid]

Re: Insignia NS-50P650A11 - Bad Power Supply?

In particular, I'd try the test pattern check that starts around 2:25. This test eliminates the main board from the circuit in addition to checking the control board and screen: http://youtu.be/JjrwTZC5nVg

I forgot to ask about the "heartbeat" indicator on the control board, which is normally an indicator of Y-main and X-main health. It should be blinking at a rate of about once per second.

Lastly, if nothing is apparent from the above test, I'd check the PSU for bad solder joints.

[tds-1541]

Re: Insignia NS-50P650A11 - Bad Power Supply?

Thank you so much for that video. I was unable to get the power supply to stay on without leaving it plugged into the main logic board. I then jumped the PS-ON connector to ground. This forced the power supply to start. After bridging the jumper on the LVDS interface (top most jumper pair) and powering the unit up, I successfully got the multicolor test patterns to show up. The 15v rail was now at 12.35v. I then removed that jumper and powered the unit up (again with the PS-ON shorted to ground) and the TV came to life and the menu's appeared as normal. This seems to indicate that the main logic board, LVDS board and the X&Y sustain/buffer units are functioning properly. After removing the PS-ON to ground jumper, the TV would not stay on, again the 15v rail never getting above 12v before the main logic board pulled the PS-ON signal signaling the power supply to shut down.

This would this seem to indicate a power supply issue. I looked at all the components on the SMPS in detail and I didn't see any bad solder joints. I'm pretty well versed in SMPS design, but this particular SMPS is very cheep online.

Think I should just bite the bullet and purchase one?

[capkid]

Re: Insignia NS-50P650A11 - Bad Power Supply?

It does seem to indicate that the PSU is bad. I'd probably attempt a component-level repair just for my own curiosity , but the board is really inexpensive to purchase.

[tds-1541]

Re: Insignia NS-50P650A11 - Bad Power Supply?

A replacement power supply arrived today and the TV fired up right away upon installation. The VS voltage was almost 5 full volts high, so I adjusted that down right away. Then I looked at VA. The panel calls for 55v. The power supply was outputting 54v. I attempted to bring VA up slightly to match the specifications, but the little potentiometer seems unresponsive across it's entire range. Very strange. Right now, the VA fluctuates between 53.7 and 54.3 depending on the picture on the screen (TV is fully warmed up). Is this an issue at all? What would a lower than spec VA look like/cause?

The TV looks okay. A little "lack luster" compared to my Panasonic G25 Plasma. I'm not sure what it looked like before the failure however, so I have nothing to compare it too.

Repair summary: Insignia NS-50P650A11 50" plasma would not power up and the power supply would rapidly click on and off every 5 seconds. The power supply (Samsung BN44-00330A) was outputting 11v on the 15v rail. A replacement power supply resolved the issue.

Thank you for your assistance, Capkid. It was much appreciated.

[capkid]

Re: Insignia NS-50P650A11 - Bad Power Supply?

Great to hear. 1V doesn't usually make much difference. It's a little strange that turning the POT had no effect.