CVP-509 Dim/Flashing screen repair

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Andromeda
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Joined: Thu Jun 22, 2017 10:53 am
Palestine

CVP-509 Dim/Flashing screen repair

Unread post by Andromeda » Fri Jun 23, 2017 3:21 pm

Hi All,

I bought my wife this piano in 2013, but she forgot to register for the extended warranty ((i)) , FFS! Luckily for her I've been dismantling things since I was a boy, so have now racked up a lot of experience over the last 30 years :) .

She turned it on the other day to find that the screen was lighting up, then going dim and off. She immediately s#!+ herself and turned it off again!
I took a look, and decided it was a power supply/invertor/lcd display issue. After taking it apart, and believe me that was the hardest part after spending so much money on it, I began to investigate the fault. Using a service manual from Yamaha, it made the disassembly a breeze.

I tested all of the capacitors and semiconductors on the power supply circuit supplying the invertor and found that they were all good. The invertor circuit had a blown capacitor, and a blown high speed transistor, which were replaced. But there must have been a reason for this.

I tested the backlight in the LCD panel itself with a standalone circuit, and whilst it lit, it was flickering slightly so I'd found the culprit! I had also previously shone a torch at the screen whilst the piano was on, and when the screen went dim, the picture still remained.

A quick scour around the web and netted poor results in finding a replacement 7.5" lcd screen, the results I did find pointed towards spending in excess of £120, for a screen that was an equivalent - not a direct replacement.

I opted for the more complicated option of finding and buying a new CCFL(miniature fluorescent tube) from ebay @ £9.90. This requires further disassembly of the actual LCD panel that I removed from the piano, using either a small craft knife and/or a guitar plectrum to gently prise the metal and plastic clips holding the lcd unit together. Be sure to take care here as any dust can ruin the overall look of the output picture on the screen. I carefully separated the 5 or so layers of plastic sheets within starting with the very fragile plate glass on top (this is what produces the picture) to get to the final acrylic sheet which has a metal clip on top. Inside the clip is the very very thin(2-3mm) fluorescent tube which needs removing, then carefully replaced with the new one and re-assembled.

After a fair bit of sweating, I am pleased to pronounce the piano back in service:-)!

If you have a questions, give me a shout.

This operation, and believe me it was, is not for the faint hearted. Some technical and soldering skills are required, and as always when working on electronics, unplug it from the mains first!

Thanks for reading.

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Buzzard
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Re: CVP-509 Dim/Flashing screen repair

Unread post by Buzzard » Thu Jun 29, 2017 5:02 pm

Welcome to the Yamaha Forums. :)

Good job, Finding the problem and solution in the same topic rocks. ((i))

Best Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea:

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