NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

[tom66]

Got another 50" plasma to repair... NEC PX-50XR5G with Pioneer plasma panel. This is a nice 1365x768 NEC plasma with HDMI. It's about 5 years old.

This one powers up with a good picture for about 10 seconds, but then shuts down with a blinking red LED, half second interval with endless count.

Found the service manual for the US version (with DVI) but it should be close enough. http://www.scribd.com/doc/41506648/PlasmaSync-50XM4. If anyone has a Scribd subscription can you please download it as PDF and PM me.

The particular error code indicates a fan event, so I need to locate the particular source of this fault.

I don't think I've ever seen a heatsink that big in a plasma TV....... that's for the Y-sustain and it's air cooled. I believe this model is intended to be mounted vertically or horizontally so it's got to have a good heatsink.

Also, it is full of Chemicon and Hitachi (primary) caps on the PSU, and Nichicon, Panasonic, Rubycon and Chemicon across the rest of the unit. Very nice. RRP - a mere £1,400.

[tom66]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

OK, some tests -

Each fan has a Vin, GND and ALARM pin. The ALARM goes high when the fan slows down too much (it's some kind of inertial switch, it's not a clock signal.)

Both fans fail with ALARM at same time, so I doubt a particular fan is giving a problem.

The supply to the fans drops BEFORE the fan ALARM signal - this is confirmed on the scope... Blue is power, yellow is ALARM (ignore spikes, they seem to be noise due to ground loops, I hope. May be a problem...)

[tom66]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

Ah, downloading the manual from Scribd is quite easy if you know how. And it doesn't involve a cent.

Simply pretend to be an iPhone 3.0 using a user agent changer in your favourite browser, and then all downloads are... free. Will upload some manuals soon, from Scribd to free manuals site in sig.

[tom66]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

Correction - blinking GREEN LED, not red.

Some more waveforms - First image shows difference between controlled shutdown (white) and plug removed shutdown. Second image shows control signal to regulator drops out (yellow) THEN regulator voltage falls (blue) - so the question is, why is the regulator control signal dropping out?

I have a feeling the error code isn't correct because the manual is slightly different.

[Securityman]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

Good luck Tom, sorry i cannot help but did not want to see you talking to your self.
I wish i could help you for once.....

[tom66]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

VERY TENTATIVE - Unplugged the speaker amp board, and it's run for at least 3 minutes now. Fingers crossed that the SP-ALM signal on it was causing difficulties.

[tom66]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

Well, over an hour running and it's still going. Plugged the speaker amp board in, and it shut down in 10 seconds. So, clearly some fault with the speaker amp. I'm going to either think about leaving it out (and mentioning that you'd need an external amp to use it with sound, as it doesn't have speakers built in anyway) or replacing the amp with a board like this. I favour the second option.

http://www.ebay.co.uk/itm/2-X-15Watt...#ht_2459wt_962

[vinceroger69]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

glad you managed to figure it out tom just looks a well built set the second option does look good at least you can sell it as a fully working set and maybe get more money for it. good to hear you got your college placement you wanted hope it goes well for you.

[tom66]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

OK, so some more tests -

The SP-ALM signal going LOW indicates a fault; with the SP-ALM high, there is no shut down. With the speaker amp board unplugged, SP-ALM goes high, and the TV works.

I then checked the outputs with a known good audio signal being fed in. The output of one amp is DC with occasional clicks downwards (every few hundred ms). The other channel is completely flat. So, I think the amplifier IC is in itself faulty. I will see if I can replace the amplifier IC by hot-airing it off, if I can get it. It's a M61571AFP by Renesas.

[tom66]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

BTW, it's definitely fixed now. I decided I don't have enough time before university to fix the amp so I'm selling it without sound. The picture is fantastic!

[yellowglasses]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

Thank You for posting.
I have a NEC PX-50XM5A
I was about to order a new power supply, then found your posting.
I disconnected my Audio board and the TV works again- same problem as you
Thank you

[Wiggly_worm]

Re: NEC PX-50XR5G - Shuts down after 10 seconds with 4 or 5 blinks

I have an NEC PX-42XR4G with a pioneer plasma panel and have a similar fault ! Might try and power it up with audio amp disconnected !!! I have six blinks from red LED on digital board and the monitor refuses to come out of standby ?