Help - MTC9000 Width/Brightness issue (fixed)

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Georgian2

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Hello,

I have this MTC9000 Chassis with this wierd issue. After ~5 minutes it slowly starts to get brighter from the inside out, not from the middle. Flipping the picture maked the same issue but on the lower side. Right after power on, if I chage the width with H. Amp the spot gets brighter and bigger as seen in this video. While the spot gets brighter, +24V on TP13 gets lower to 23V.

Any experts here who could help me? I did change to Flyback and all caps seems to be good.

Thanks a lot guys.,


Georgian22023-02-04 17:44:04
 
G

Georgian2

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Yes, it did. The chassis came with an burned isolation between hot and heatsink. Replaced both and now this issue. There was no proper short but a tiny gap tht made noises and tiny sparks.

Older flyback works fine on another chassis. every single resistor I test with one pin lifted up test good and capacitors soldered in tests also good...
smiley19.gif


I did notice that on realy cold starts there is some sync issue for about 10 seconds. No rolling but pixels messed up horizontaly on a few lines. didn't bother to take a picture. Could this be related?
 
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gunblade

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c36 3n9 1600v

c40 6n8 1600v

does sub brightness pot function correctly?

and when you say caps are good do you mean you removed each one and read them with a capacitance meter or are you just guessing as they look ok?
 
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Georgian2

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I tested them in circuit with capacitance meter. Most of them are replaced(electrolytic ones) . Will swap the C36 and C40 so see if any change. Preset brightness works too. 220k Potentiometer is new too.
 
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Georgian2

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Did change the two and no much of improvemand.

I did notice that if the H.Amp is turned al the way anti clockwais(wide picture) then all the way clockwise (narrow picture) the picture stays narrow for 2-3 seconds than starts to widen up itself and to get brighter. Again h amp all the way to the left (wide and bright image)than quick to the right (narrow and no bright spot) than it start to widen up itself...

Hope you underdstand what I mean.

Georgian22023-02-02 23:15:20
 
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Georgian2

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B+ is 130,3...5 stable.

Id did try it with 2 Hantarex tubes, both known working (14" and 16") and same issue. I don't have the origal tube and the chassis dosen't have any modifications on it. Any chance that it is for 20"+ tubes or something? and the ones I'm using are to small?

12V is stable, 26V is 24V and then 21 after R6 33Ohm.
 
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gunblade

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unstable vertical hold is normally one of the transistors in the sync circuit but that does not explain your horizontal size and the brightness issue
 
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