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Motorcycle Repair/87 Yamaha Venture Royal computer monitor display issues.

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Question
QUESTION: Lazaros,

Iím working on this 87 Yamaha Venture Royal.  The computer monitor display was working fine.  The other day, while riding, for some reason the computer monitor display screen dimmed and has not come back to its normal brightness.  I can see when it goes through its start up test and all the symbols light up, and then after it completes the test, the screen is dim.  I can see the fuel level if I look close enough, but somethingís is not right.  What might I check to see why the screen has dimmed?  I did pull the computer monitor out and looked it the solder joints and checked the connections.  All looked good.

Illumination control knob
Illumination control k  
ANSWER: Hello Robert,

Most probably, the illumination control potentiometer is malfunctioning due to moisture or dust.

Try turning the knob fully clockwise and then anti-clockwise several times. If it doesn't get better, you must take the panel apart and clean the potentiometer with contact cleaner spray.

Keep me posted.

Best Regards,
Lazaros.

---------- FOLLOW-UP ----------

QUESTION: I should have added that the lights for all the gauges all work and change from brighter to dimmer and vice versa with the illumination knob.  It's only the computer monitor screen that is dim.  Does the illumination knob control the brightness of the computer monitor screen as well as the brightness of the other dash lights?

ANSWER: Hi Robert,

In that case, the backlight must be blown, or, has bad connection.

I'm not sure if the backlight is a common bulb with a reflector, or, LED on the printed circuit of the computer monitor.

You have to take the meter panel apart and check it out.

You can take pictures and send them to me, if you can't figure out the illumination pattern.

Best Regards,
Lazaros.

---------- FOLLOW-UP ----------

Back view
Back view  

Inner
Inner  
QUESTION: Lazaros.
Hi again.  After our last messages back and forth, you were unavailable.  Since your back and I still cannot get my message center to be readable, I took it apart and snapped several photos.  Here is what I got.  I hope you can tell me what to cheek or fix to get the, what I believe is a led to be brighter.  It will only let me upload two.  I have several more. Thank you.

Answer
Hello Robert,

I was recovering from a rather nasty accident, good to be back.

As I saw in the pictures, there is a Lexan or Plexiglass piece (clear-like-glass) that (I guess) goes under the LCD. Looks like a backlight reflector. The round-cut protrusion of it, looks like a bulb reception.

What I need you to do is, upload a photo of the front side (screen) and one of the rear cover where the bulbs are.
In any case, the bulb that's next to the LCD assembly should be the backlight of it.

At this point, I apologise for not being more precise, and the reason is that this model never came in Greece, and all I'm doing is guessing, based on general knowledge on Yamaha's electrics/electronics.

Best Regards and a Happy New Year,
Lazaros.

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Lazaros Ampatzidis

Expertise

I can help you on EVERY issue involving POST-1980 Japanese Motorcycles plus KTM and Husaberg. My field of expertise includes Engine, Transmission, Fuel system (carburation & EFI),Electrics and Electronics. Maintenance, repair and tuning. Road and off-road suspension tuning. Please don't ask me about non-Japanese Motorcycle, especially American built on which I have low to zero experience.

Experience

I'm a rider and hobbyist since childhood. 25 years motorcycle workshop mechanic.15 years motorcycle racing mechanic. In order of experience high to low:Kawasaki,Suzuki,Honda,Yamaha,KTM,Husaberg.

Education/Credentials
Hellenic (Greek) Technical School.Internal Combustion Engines Engineer. Automotive Electronics.

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