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Author Topic: MS8-26SU with dim/noisy image  (Read 514 times)

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MS8-26SU with dim/noisy image
« on: November 14, 2017, 12:39:36 pm »
Edit - I was able to mostly solve this brightness issue by replacing C332 on the neckboard per recommendation, finding a couple more questionable solder points, cleaning the RGB gain and bias pots, and adjusting accordingly. I still have some slight image noise and breathing effect so maybe a whole kit would help.

I have a MS8-26SU that I am a bit stumped on.

After getting everything setup I'm getting an extremely dim image that has a lot of wavy noise in the background.

As far as I know through testing my signal source is clean. The brightness pot needs to be at about 80/90% before a reasonably bright image appears and is pretty much blank in the lower 70%.

I measure perfect B+ with 92V on the test points, I have a good syncing source, there are no obviously leaking capacitors, no excessive 15khz noise, and no obvious deflection or geometry issues, so I am unfortunately a bit stumped.

There were a few bad/dry solder joints but nothing too crazy, and I didn't fix anything by re-flowing the bad joints. The chassis does have the classic Nanao heat damage near the center, but there doesn't appear to be any lifted pads and all large resistors seem to test OK! (I haven't measured all of the tiny ones)

In the mean time I have some capacitors on the way and will do a little more digging into the neck board. I've read on NG forums that the electrolytic on the neck board can be the culprit for dark image, but I will believe it when I see it.

If anyone has any ideas let me know! The convergence and geometry adjustments I can handle. I just hope I don't have a bum tube.
« Last Edit: November 14, 2017, 10:51:29 pm by furntree »


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