Lines and clicking sound at low brightness -- Nanao MS8-29FA

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yosinlpet
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Lines and clicking sound at low brightness -- Nanao MS8-29FA

Post by yosinlpet »

Hi,

I had an issue with horizontal hold on my astro city.
I took it apart and figured out cap C911 of the MS8-29 chassis was dead. So i bought a set of replacement caps and recapped everything [besides C560, C561, C521 (330uF 16V instead of the referenced 33uF 16V), C446 (33uF 16V non polarized) and the huge 1000uF 180V cap]
I also resoldered some cold joints here and there.

I was rather surprised when recapping because all new caps (rubycon -55°C +105°C) showed a smaller capacitance (within tolerance) than the nominal value. On the other hand, except for C911 which was dead, each cap I took off my chassis was overshooting the nominal value (within tolerance). I took care to measure the value of every cap I soldered and i double-checked their polarity.

Even though the connexions were all sound and solid, it took several shots for the screen to turn on.
But then when it did... To my great deception, here are the results:




So i get Horizontal or Vertical white lines on top of my image;
The image is unstable and a there is a loud repeated clicking sound if the brightness of the image is too low.
I tried different pcbs and they all undergo the same problem.

To conclude on a positive note: replacing C911 solved the H-Hold issue :lolno:

Do you guys have any idea what could be responsible? Thanks for the help


EDIT: Changing caps messes up with the screen and focus adjustments on the flyback. IT WORKS NOW! Thank y'all!
Last edited by yosinlpet on October 5th, 2020, 8:59 am, edited 3 times in total.
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grantspain
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Re: Lines and clicking sound at low brightness -- Nanao MS8-29FA

Post by grantspain »

did you replace the 10uf cap on the neck card?
yosinlpet
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Re: Lines and clicking sound at low brightness -- Nanao MS8-29FA

Post by yosinlpet »

Yes and just to be sure the new cap was not defective, i put it back; same stuff. Then I re-replaced it.

I wonder if I didn't screw a transistor up when consolidating cold joints. But I have a 95W soldering station working at 340°C, I never stayed more than 5sec on the same spot.

Or is it possible by applying a little shear stress on the flyback wire when soldering, it caused leakage there and this is why we ear arcing? but then what has the brightness to do with that ? and why the visible lines? :eh:
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grantspain
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Re: Lines and clicking sound at low brightness -- Nanao MS8-29FA

Post by grantspain »

these are delicate chassis and tracks break easily, also worth checking the crt socket
check to see where that clicking is coming from- is it from the neck area of the tube or the chassis itself
yosinlpet
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Re: Lines and clicking sound at low brightness -- Nanao MS8-29FA

Post by yosinlpet »

I solved it! Everything works fine! thanks for the help :)

Just needed to adjust b+ setting :roll:
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grantspain
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Re: Lines and clicking sound at low brightness -- Nanao MS8-29FA

Post by grantspain »

should be about 92v
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