K7901 C4/5/6 cap orientation

ieure

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I'm in the middle of recapping this K7901 and I'm stuck on the C4/5/6 caps. The old ones have no +/- markings, there's nothing printed on the PCB, and nothing in the PCB map in the manual. Looking at the schematic, it seems that the positive side should connect up with R10:

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Which would mean that this is the positive side:
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Does this seem correct?
 

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Aha. I see that these are non-polarized caps, so orientation doesn't matter.
 
Yup… Fired it up and it plays fine. I'm still seeing some blurriness in the center of the screen that I'm not sure about, though. I'll read up and see what I can figure out.
 
let it warm up for a minimum of 15min and adjust the focus control on the flyback.

if you look at the fly and it has wite knobs i would replace it. as they get cracks in them causing the focus to drift.
the black nob fly's have had bad crackes in them as well. you may need to clean it off with a rag to see them.

and if you have not cleaned the face of the tube do that as well. you would be surprised on how dirty they can get.

Peace
Buffett
 
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let it warm up for a minimum of 15min and adjust the focus control on the flyback.
I'll do that.

if you look at the fly and it has wite knobs i would replace it. as they get cracks in them causing the focus to drift.
the black nob fly's have had bad crackes in them as well. you may need to clean it off with a rag to see them.
It does, unfortunately. The thing is that the edges are crisp, it's only the center that isn't. I was hoping I wouldn't have to do the fly, but it looks like I might. I'll fiddle with the adjustments before I go down that road, though.

and if you have not cleaned the face of the tube do that as well. you would be surprised on how dirty they can get.
For sure. I did that when I did the caps. My Asteroids Deluxe was previously in a smoker's house, and the monitor and plexi were caked with a thick layer of dust and tar. Really, really nasty stuff. I had to use Goof Off to get it off the monitor — plain glass cleaner was ineffective.
 
yea it sucks that stuff cant last a 100 years or more but you know how it is.

i would change it as a precaution. as it will take more things with it if it blows. the focus is directly controled by the fly and if it wont adjust out then a new fly is what it will need.

good luck with it.

Peace
Buffett
 
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