Insignia NS-P502Q-10A Suspected bad Y-Main Board

[thewilly]

This is the first I've messed with a TV. I have experience with analog guitar amplifiers and general household electrical.

My 50" Insignia plasma turned off while I was watching it. When I tried to turn it back on it would click and try to turn on then shut itself off. I did some reading then opened up the back and started troubleshooting. I believe it is the Y-Main board, there is also a separate Y-Buffer on this model.

I looked over the tops of the boards and did not see any apparent damage or burns and checked all removable resistors for continuity and they passed.

I disconnected the cable to the Y-Main board and powered it up, the TV turned on and stayed on.

I reconnected the Y-Main and disconnected the Y-Buffer. The TV turns on then shuts itself off.

I inspected the Y-Buffer when it was out and didn't see any indications of burnt components. I did not fully remove the Y-Main but do not see an issue from the top of the board, there's no bulging caps.

I think I've got it isolated to the Y-Main.

Should I replace both the Y-Main and Y-Buffer or would I be safe to just replace the Y-Main for now to see if that fixes it? Or if it turns out to be the Y-Buffer would I risk frying my new Y-Main if I don't replace both at once?

Thanks for the help!

[ReeceyBurger123]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Seems like the Ymain but I aint helping further till you help us. Thanks.

[thewilly]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Seems like the Ymain but I aint helping further till you help us. Thanks.

sure, happy to help. whatcha lookin for?

[ReeceyBurger123]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Pictures and meter readings please, use the search feature and google to help you along the way. Test the Psu Vs and Va voltage with and with out Y connected and Ysus voltages.

[thewilly]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Pictures and meter readings please, use the search feature and google to help you along the way. Test the Psu Vs and Va voltage with and with out Y connected and Ysus voltages.

Here are readings with the Y-main disconnected:

With the Y-main disconnected the TV stays turned on

PSU Vs: 209
PSU Va: 56

These are both per the spec label.

Here are the readings with the Y-main connected

With the Y-main connected the TV turns itself off then attempts to turn on again a few seconds later then shuts off again and continues in this loop.

PSU Vs: 0.8
PSU Va: peaks at 22

Y-main VScan test point: peaks at 0.4

I didn't notice other test points on the Y-Main board

I have not tested pins to the Y-buffers

I have checked all fuses for continuity and they pass

Here is a link to view high res photos: https://postimg.org/gallery/1ca5xxp08/

Full TV Back:


Spec Label:


PSU Board:


Y-Main & Y-Buffer:




Thank you for the help! Please let me know if I need to pull more readings and what the next step is.

[thewilly]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Here are readings with the Y-main disconnected:

With the Y-main disconnected the TV stays turned on

PSU Vs: 209
PSU Va: 56

These are both per the spec label.

In case that wasn't clear, the voltages read exactly as expected, I didn't just post the label voltages

[ReeceyBurger123]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Ok what does Vsc do please ? Also these sets are known for a bad Ymain and buffer, same as a Samsung B550.

[thewilly]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Ok what does Vsc do please ? Also these sets are known for a bad Ymain and buffer, same as a Samsung B550.

I didn't see a test point for "Vsc", I did see one labeled VSCAN on the Y-main board. It's not visible in the photos, its jammed in there next to a large transistor and my photo angle doesn't catch it.

I guess the Vsc test point is labeled VSCAN and located on the Y-Main?

I tested the VSCAN point with the Y-main power cable connected, which means that the TV would power on then auto shut-off. The voltage peaked at about 0.4V before the TV shut off.

I just went and tested the VSCAN point with the Y-main board disconnected and it read -130. I didn't test it before because with the cable disconnected I wasn't expecting it would read anything

I checked the Ve too. With the Y-main disconnected (TV stays on) it reads 87. With the Y-main connected (TV powers on then shuts off) it peaks at 0.4.

Thanks for all the help!

[ReeceyBurger123]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

So Vscan on the Ymain with the buffer out stays at -130 ?

[thewilly]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

So Vscan on the Ymain with the buffer out stays at -130 ?

Vscan with the main power cable running to Y-main disconnected but the buffer board connected reads at -103 (130 was a typo)

I have not tested it with the buffer board pulled out

there is another small power cable at the bottom of the y-main that connects to a logic board, i've left that connected for every test.

[thewilly]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

So Vscan on the Ymain with the buffer out stays at -130 ?

With the buffer board pulled out the VSCAN measures around 0, whether or not the power cable from the PSU is connected. There is another power cable between the Y-Main and a logic board that seems to supply some current.

With the buffer board installed and the power cable from the PSU disconnected the VSCAN reads -103. With the PSU power connected the TV automatically shuts itself off, the voltage on VSCAN climbs to less than 1 volt before it turns off

[ReeceyBurger123]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Ysus is faulty then.

[thewilly]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Ysus is faulty then.

Thank you! Would you recommend replacing but the Y-Main and the Y-Buffer at once or would I be safe with just the Y-Main?

[steves7839]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Coppell TV blog has weighed in on this question re a similar Samsung plasma Panel, S42AX-YD01. Search their blog for LJ92-01200A. PlainBill has also weighed in on this forum with an opinion to replace both. Search for the thread "Philips 42PF7320A/37 42" Plasma Repair"

[thewilly]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

Coppell TV blog has weighed in on this question re a similar Samsung plasma Panel, S42AX-YD01. Search their blog for LJ92-01200A. PlainBill has also weighed in on this forum with an opinion to replace both. Search for the thread "Philips 42PF7320A/37 42" Plasma Repair"

Thanks! Those were very informative. I'd suspected that replacing both would be the best/safest option.

[vinceroger69]

Re: Insignia NS-P502Q-10A Suspected bad Y-Main Board

http://blog.coppelltvrepair.com/2010...according.html