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Author Topic: Dark picture on U5000  (Read 2109 times)

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SirPeale

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Dark picture on U5000
« on: November 17, 2006, 09:33:32 pm »
Pulled out a Cruis'n game to shop out yesterday.  Picture was awfully dark.  The screen control is turned all the way up, and so are the contrast and the brightness.

Pulled the chassis, tried it on a known good tube, still dark.

Capped the entire chassis.  No change.

B+ is 120V.

The brightness control does practically nothing from one end of the pot to the other.  The contrast, OTOH, if you turn it all the way down you get a black/white picture.  Turn it up, it goes dark, then you start seeing a picture. 

Guessing a resistor somewhere has gone out of spec, but which one?

And yes, I've tried other (known good) neckboards.

Ken Layton

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Re: Dark picture on U5000
« Reply #1 on: November 18, 2006, 12:16:31 am »
Picture tube needs to either be rejuvenated or replaced. Probably has one of those crappy Zenith tubes in it that Wells was famous for using.

grantspain

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Re: Dark picture on U5000
« Reply #2 on: November 18, 2006, 12:27:37 am »
i know its not any help but i really hate the u5000 chassis

Ken Layton

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Re: Dark picture on U5000
« Reply #3 on: November 18, 2006, 01:39:41 am »
Ah yes, the U-5000.  ::) Another one of those "what was Wells thinking?" monitors. :laugh2:

grantspain

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Re: Dark picture on U5000
« Reply #4 on: November 18, 2006, 01:42:55 am »
was it not this chassis that if you left the remote board disconnected it  blew the living poo out of the psu circuit

SirPeale

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Re: Dark picture on U5000
« Reply #5 on: November 18, 2006, 06:55:50 am »
Picture tube needs to either be rejuvenated or replaced. Probably has one of those crappy Zenith tubes in it that Wells was famous for using.

Nope...you didn't you see above..."known good tube".  Other chassis work fine on these tubes.

Ken Layton

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Re: Dark picture on U5000
« Reply #6 on: November 18, 2006, 10:56:28 am »
Does this have an LM1203N chip on the neckboard? Is there a 12 volt zener diode (or any other voltage zener) on the neckboard? If so, check the 12 volts going to the LM1203N.

The LM1203N is a high failure chip.

grantspain

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Re: Dark picture on U5000
« Reply #7 on: November 18, 2006, 04:39:22 pm »
please don't shoot me but have you checked the monitor with a colour bar generator just in case its some strange voltage/signal problem on the cab

SirPeale

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Re: Dark picture on U5000
« Reply #8 on: November 18, 2006, 09:49:31 pm »
please don't shoot me but have you checked the monitor with a colour bar generator just in case its some strange voltage/signal problem on the cab

I've ran this chassis on both the original cabinet and in our test bench.  Good suggestion, but that's not the key here.

Does this have an LM1203N chip on the neckboard? Is there a 12 volt zener diode (or any other voltage zener) on the neckboard? If so, check the 12 volts going to the LM1203N.

The LM1203N is a high failure chip.

I've tried multiple neckboards as well.  With definitely known good neckboards.  I will check the voltage when I go back to work on Monday.  But my guess is it's somewhere on the main chassis.  Resistor out of spec or something.

worm

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Re: Dark picture on U5000
« Reply #9 on: November 18, 2006, 10:42:04 pm »
There is a IC chip on the chassis I think LA7851 that help control that.
I am alway willing to learn, so please share the knowledge.

SirPeale

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Re: Dark picture on U5000
« Reply #10 on: November 28, 2006, 06:37:08 pm »
This problem is now fixed.

I contacted the monitor repair tech from East Coast Amusements.  They're who we send 99.9% of our monitor chassis to when we either don't have time to fix them ourselves or if we can't figure out what's wrong.

I was told to check resistor R811.  It often goes open on these, and causes this exact symptom.

R811 is a 100K resistor (brown black yellow) and I'm guessing it's 1/4 watt.  Managed to find *one* brand new one in the parts drawer.  Pulled the old one...yep...open.  Popped the new one in...success!  Bright, vibrant picture!

Had a second chassis with a similar issue.  Pulled the resistor...open.  Pulled one off a parts chassis.  Back in business!

Looks like we'll have to get a few of these for the parts drawer.

Just wanted to post in case someone else has this problem!

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Re: Dark picture on U5000
« Reply #11 on: February 26, 2018, 05:34:32 pm »
Thank you for your follow up on this. U5000 eating me alive lately and this saved me a LOT of searching. Thank you!

Ken Layton

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Re: Dark picture on U5000
« Reply #12 on: March 06, 2018, 10:42:23 am »
Yes, resistor R811 going bad will cause a dark or black and white picture.

  
 

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