Hitachi Projection TV loss of Brightness


  #1  
Old 03-14-02, 03:57 PM
William Michael
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Unhappy Hitachi Projection TV loss of Brightness

My Hitachi 55 inch rear Projection color TV ( Model number 50UX58B) is 3 years old. It has a loss of Brightness especially in the darker portions of the image. This degradation has progressed over the past 3 months to mostlly unusable. I played the DVD a couple of weeks ago and it looked fair but not as bright as usual. This week the DVD image is darker with green skin tones. Could not get the Green out with color adjustments. DVD is connected to the component input and the cable TV is connected to the S-Video input. The skintones on cable TV are fair but now going dark like one F-stop off. The contrast from light to dark is from one extreme to the other...Whites are bright and dark colors have no detail. Any schematics with parts list posted on the net? Anyone out there with an idea on how to resolve my problem?

Thanks,
Bill
 
  #2  
Old 03-14-02, 06:12 PM
Smokey
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Good evening, William Michael:

I perceive you have a failure in the regulation of the power supply that is providing the G-2 voltages to the projection tubes. G-2, the second grid, is the element that drives the electrons to the face of the screen and developes the concept of "brightness".

You have a good situation to call for a technician to service the set. This is something that will not get better with time.


Smokey
 
  #3  
Old 03-14-02, 06:43 PM
William Michael
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Hitachi Projection TV loss of Brightness

Smokey,

The shops in Orlando Florida want to take the set to the Shop for $100 round trip plus $75 investigation fee. They said if were a module you could add another $300 to the price tag.

Is there a way to check this out myself? I have performed some minor repairs of lightning damage in some of my other TVs in the past down to the piece part level. This included a tuner shorted diode and input power supply.

Would the fix for this regulation problem be a part replacement or a module replacement?

Thanks,
Bill
 
  #4  
Old 03-14-02, 07:02 PM
Smokey
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You need a service manual so you have some idea what you are doing and what you are looking at. Best place to get the manual is at
http://www.treasurechestcorp.com/Default.htm

Once you have the manual, we can discuss on site help.


Smokey
 
  #5  
Old 03-19-02, 05:43 PM
William Michael
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Hitachi Projection TV loss of Brightness

Smokey,
I have the service manual from your suggested source...They have quick turnaround. So where do you suggest I go from here? I will have an O-scope this later this week. I have test meters but no signal generators.

Thanks,
Bill
 
  #6  
Old 03-20-02, 01:24 PM
Smokey
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Check the G-2 voltages on the board/socket on the projection tube. If it is low (and I suspect it is), then trace it back to the power source to find out why.

Smokey
 

Last edited by Smokey; 03-20-02 at 08:56 PM.
  #7  
Old 03-22-02, 06:26 AM
William Michael
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Hitachi Projection TV loss of Brightness

Smokey,
I finally decided to take a vacation day and get to work on the subject problem. When I took the back off the TV I noticed the high voltage (G2) wires were in contact with the Focus box wires and some others. Looked like they settled over time. I dusted off the high voltage section and moved all the wires contacting the High Voltage (G2) line. The end result was it fixed my problem. Without the service manual you suggested and your kind help I would never have found the problem. Thank you so very much for your help. Keep up the outstanding help on line.


Bill
 
  #8  
Old 03-22-02, 06:09 PM
Smokey
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Another plus for the guys in the white hats. I sent a copy of your post to the folks that provided your service manual. It makes them feel good, too, knowing they provided the information.

Smokey
 
 

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