NEC PX-42VP4g plasma goes into standby


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NEC PX-42VP4g plasma goes into standby

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Rodoz6
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Mar 8, 2009, 2:31 AM

Post #1 of 22 (21671 views)
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NEC PX-42VP4g plasma goes into standby	Can't Post

My NEC PX-42VP4g plasma panel goes into standby when I turn it on Its boots up runs for 5 seconds and then shuts down to standby. Checked the supplies. The HV 170v supply begins to drop after turn on the cuts off back to standby when it drops tp about 136V. Picture does appear ok before switches itself off. Replaced a couple of caps with low readings and poor ESR but all the others look fine. No schematic for me to work with. Can any body help with this problem? It is evidently a common one for this series but none of the databases seem to have a fix posted. Unusual for such a known problem. This one has me baffled.

I hope someone can advise me how they fixed theirs

Regards Rod

denonjapan
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Mar 8, 2009, 4:30 AM

Post #2 of 22 (21651 views)
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Re: [Rodoz6] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

All i know about NEC monitors are with built-in fans. did u check those 2 are working properly?

denonjapan
made in japan

Rodoz6
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Mar 24, 2009, 12:08 PM

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Re: [denonjapan] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

Thanks for the message This model has no fans. I have searched the internet with lots of hit on this power supply but no answers or schematics. Evidently these units have quite a history for supply issues. It is made in China and I suspect a number of plasmas used this unit.
The supply inside is PKG-1953, Origin, CMKY-C2x. I am an electronics tech but I need a circuit to fix this baby as there is so much surface mount.

anyway thanks for your response Very much appreciated.

Regards from Rod

techchris
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Mar 24, 2009, 12:33 PM

Post #4 of 22 (21629 views)
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Re: [Rodoz6] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

the chances of getting any technical info on something made in China is zilch.it may be worth checking electrolytic capacitors in the power supply first to see if any have dried up or gone open circuit

Rodoz6
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Mar 28, 2009, 11:17 PM

Post #5 of 22 (21615 views)
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Re: [techchris] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

Thanks I am still hoping someone has a schematic as I have been through all the caps on board, impedance and capacitance checked and all are fine. To the best of my determination the fets and power devices are functional as I have metered all possible junctions. Apart from the detail I've already posted on the PCB the info tag on the heat sink tray of the supply PCB is identified as PNT-426 made by Origin Electric Co. LTD. I suspect there are schematics around but more than likely not found by western search engines. I may try to see if someone can search using a chinese search engine. I have read so many requests from techs and novices alike that have these units faulty so there must be someone out there with a schematics. If I find one I will post it for sure. Thanks for your input and please keep an eye out for a schematic for me. Regards from Rod

Rodoz6
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Jun 3, 2009, 12:18 PM

Post #6 of 22 (21369 views)
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Re: [techchris] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

Further information on the power supply. The supply is not NEC but Origin Electric Co China supply model PNT-426, pcb PKG-1953. I believe it may be used in other plasmas too. I replaced any caps that had poor ESR readings. Supply ran but the 170v rail would slowly drop from to about 136v then supply would go into standby. Picture was fine until about 145v then a bit noisy. Eventually with me turning it on and off to diagnose rails the supply failed. Now I can see B+ HV DC pre regulator. Also 5v out of 74L05 for standby but turned off by protection before leaving the board to standby switch. Choppers not running.

numan2good
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Jun 3, 2009, 3:33 PM

Post #7 of 22 (21365 views)
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Re: [Rodoz6] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

hello Rodoz6
well i guess the Chinese made TV do occur with these kind a problems.but the thing is if this problem have a solution.if the TV set is repairable or you can find the exact model spare part of it.

Bella123
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Aug 3, 2009, 11:51 PM

Post #8 of 22 (21079 views)
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Re: [Rodoz6] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

I just inherited an old NEC PX-42VP4G/S. It is a plasma monitor. It does not have any in-built tuners.
I had the same problem when I switch it on . It used to go off after 20-30 seconds. I do not have a user manual or a remote control for it. So I relied on my previous experience in operating so many different types of TVs, monitors and computer equipment.
I connected it to a separate Set top Box to Video 2 with Audio 2 using RCA cable. In the advanced OSM, I chose picture mode "THEAT 2". It works. Try this option see if it works for you.
My problem though is that the unit lost its brightness. The picture is dull. It is clear. The colours are perfect. To avoid old burning marks I had to reduce the contrast to the lowest setting.
I noticed you are an electronic engineer. Maybe you can help me in identifying this problem. I can fix things I got all the soldering materials. Measuring meters, but I am not an electronic whiz. I can replace components with guidance.
The other thing I am chasing up is a remote control for it and a user/service manual for it.
I hope you can help me.

denonjapan
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Aug 4, 2009, 4:26 AM

Post #9 of 22 (21069 views)
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Re: [Bella123] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

That's the reason being you inherit the display... the original owner had known the defect. He didn't want to tell you, into thinking "you got a bargain"..

denonjapan
made in japan

Bella123
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Aug 4, 2009, 6:31 AM

Post #10 of 22 (21067 views)
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Re: [denonjapan] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

Hi,
Now that we know, can it be fixed and how?
Has anyone in your forum got a PDF copy of the manual? be it the owner or the service one.
Regards

denonjapan
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Aug 5, 2009, 3:13 AM

Post #11 of 22 (21061 views)
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Re: [Bella123] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

To be honest with you, No IT CAN'T BE FIXED. The problem is the entire screen. that's all you ought to know. take care!

denonjapan
made in japan

Bella123
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Aug 5, 2009, 7:21 AM

Post #12 of 22 (21057 views)
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Re: [denonjapan] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

Hi,
Many thanks.

addi
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Aug 10, 2009, 10:04 PM

Post #13 of 22 (21021 views)
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Re: [Rodoz6] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

carrera2
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Aug 22, 2009, 10:40 PM

Post #14 of 22 (20950 views)
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Re: [addi] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

I was having a similar problem with an acquired broken plasma and replaced the 3 HV capacitors and the power supply now seems to run normally. Voltage is 170v without any input, then drops to around 140V with a mainly white screen, 140V to 150V with normal pictures. 60V measures around 61.1V and 5V is just 4.71V
It does suffer from image retention and what could be described as mal discharge when the scene is bright.
How does this compare to other peoples screens / measurements. Is this a residual power supply problem, or some other issue eg with the scan board ?

kdh2010
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Jun 21, 2010, 9:38 PM

Post #15 of 22 (19545 views)
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Re: [Rodoz6] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

To All:
Sorry this is late, but for anyone else who needs this info - here it is.
If your 170v is loading down when the tv is turned on, it is one or more of the current sense resistors making a poor contact.
They are .47ohm surface mount resistors. There are three of them located right by q14 & q15, near the largest capacitor on the board. Resolder them (both ends of all three of them), or replace them with a .15 ohm resistor.
Hope this helps.
Dan

carrera2
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Feb 12, 2011, 6:40 PM

Post #16 of 22 (18570 views)
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Re: [kdh2010] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

In Reply To

Dan,

You information is certainly not too late...............

Having put the screen away until I had more time, I finally dug it out again today. I re-ran the test and then re-soldered the three resistors you identified.

What can I say except:

Many thanks, grazie mille, tusen tack, muchas gracias, merci beacoup, danke sch�n, dank je wel , ta very much! Cool

(that's about the limit of my language abilities)

I have now repaired both my screens, and identified that the resistors are the problem on a third power supply I have. Wooo Hoo !

All the very best, you are a star Angelic

kdh2010
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Feb 12, 2011, 11:46 PM

Post #17 of 22 (18565 views)
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Re: [carrera2] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

I'm glad that the info was useful. Thanks for the kind words and congratulations on your repairs!
Dan

jlo970
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Aug 6, 2011, 10:36 PM

Post #18 of 22 (17662 views)
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Re: [kdh2010] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

Hello - could I get some advice please? I have the same issue with my PKG-1953 power supply but I'm not sure which resistors you're referring to by q14 and q15. Are you talking about R135, R140, and R141? Or is the teeny tiny surface mounts above those? I'm new to this whole thing so any advice would be greatly appreciated. I can send a picture of the board for markup if that would help....

Thanks,

Jim

kdh2010
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Aug 8, 2011, 4:18 PM

Post #19 of 22 (17642 views)
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Re: [jlo970] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

Hi,
I don't remember the details anymore, and don't have a board in front of me.

With that said, R135,140 & 141 sounds right. They are surface mount resistors, but are pretty big (for surface mount).

They should be labeled with a 47.

Hope that helps.

DPMS
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Jan 10, 2012, 2:05 AM

Post #20 of 22 (16065 views)
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Re: [kdh2010] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

http://s1219.photobucket.com/albums/dd425/DishProMediaServices/

these little resistors seem to have friends on the left that couldn't take the heat either. The large 200v 1500uF cap is bulged and needs to be replaced. However, there is a 8 legged chip that blew its top in the middle with great gusto as well. Is this the same value as the ones below on the board, or what part # is this item.

Looking for the fix of course...

kdh2010
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Jan 15, 2012, 11:39 PM

Post #21 of 22 (15963 views)
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Re: [DPMS] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

Hi,
Sorry I can't help much. I don't know what the value of the blown resistors are or the part number of that IC.

It's been a long time since I worked on that board.

Shop Jimmy has real good pictures, usually, and maybe we could see the part numbers. But, I checked and I don't think they have this board at this time.

So, my best advice is to search the web for a good picture and try and get the values there.

BTW, Q14 & Q15 are probably shorted, too.

Sorry that I couldn't help more.
Dan

DPMS
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Jan 16, 2012, 12:18 AM

Post #22 of 22 (15959 views)
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Re: [kdh2010] NEC PX-42VP4g plasma goes into standby [In reply to]	Can't Post

Oh, well thanks for the reply and heads up on Q14 and Q15. I would not even thought of changing these out because physically they seem to look fine. I am not familiar with "Shop Jimmy" but will Google it and try and find these part #'s.
If you find pic's post them as they would really help. At least my pic gives you a reference point to a seemingly weak link problem.
Thanks!
Russ.

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