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Crumbtrail TV Forums: TV Equipment: Plasma TV Forum:
NEC PX-42VP4g plasma goes into standby

 
 


Rodoz6
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Mar 8, 2009, 10:31 PM

Post #1 of 15 (2379 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
Veteran

Mar 9, 2009, 12:30 AM

Post #2 of 15 (2371 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
New User

Mar 25, 2009, 8:08 AM

Post #3 of 15 (2351 views)
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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
Veteran

Mar 25, 2009, 8:33 AM

Post #4 of 15 (2349 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
New User

Mar 29, 2009, 7:17 PM

Post #5 of 15 (2335 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
New User

Jun 4, 2009, 8:18 AM

Post #6 of 15 (2089 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
New User

Jun 4, 2009, 11:33 AM

Post #7 of 15 (2085 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
New User

Aug 4, 2009, 7:51 PM

Post #8 of 15 (1799 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
Veteran

Aug 5, 2009, 12:26 AM

Post #9 of 15 (1789 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
New User

Aug 5, 2009, 2:31 AM

Post #10 of 15 (1787 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
Veteran

Aug 5, 2009, 11:13 PM

Post #11 of 15 (1781 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
New User

Aug 6, 2009, 3:21 AM

Post #12 of 15 (1777 views)
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Re: [denonjapan] NEC PX-42VP4g plasma goes into standby [In reply to] Can't Post
Hi,
Many thanks.


addi
New User

Aug 11, 2009, 6:04 PM

Post #13 of 15 (1741 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

For more http://www.telekomx.mobi/lp2/iwaay


carrera2
New User

Aug 23, 2009, 6:40 PM

Post #14 of 15 (1670 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
New User

Jun 22, 2010, 5:38 PM

Post #15 of 15 (265 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

 
 
 


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