Author Topic: 8590 series CRT slant  (Read 495 times)

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Offline veedub565

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8590 series CRT slant
« on: June 19, 2021, 08:13:09 pm »
I have a HP 8590 series SA with a decent display, but it's slanted and I don't see any adjustment for that. Any idea what needs tweaking here ?
 

Offline MarkL

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Re: 8590 series CRT slant
« Reply #1 on: June 20, 2021, 12:39:28 am »
It doesn't look too bad, but if it bothers you...

You need to open the CRT case and slightly twist the magnetic deflection assembly (aka "yoke") that sits on the neck of the CRT.  I haven't opened the CRT on the 859x series specifically, but there should be a compression clamp on the yoke that you will have to loosen first.  Even after loosening the clamp the yolk may be stuck after being on there for many years.  Be gentle.

Safety notes:

- There is high voltage in this area and in other areas inside the CRT case, even when off.

- When done, don't over tighten the clamp because too much pressure can cause the CRT neck to crack or shatter.

There are some youtube videos on CRT yoke adjustment if you search for them.
 

Offline veedub565

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Re: 8590 series CRT slant
« Reply #2 on: June 24, 2021, 07:50:05 am »
I think rotating the yoke would rotate the whole image. The horizontals are fine it's the verticals which are a bit skewed, especially towards the right hand side. I've been having a read, and wondering now if it's a problem with the S correction. I've had a couple of these CRT's where the capacitors have changed value with age and it's killed the drive. Maybe a similar thing has happened here. I'm going to try a ew capacitor in the deflection circuit and see if that helps. 
 

Offline MarkL

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Re: 8590 series CRT slant
« Reply #3 on: June 25, 2021, 03:38:05 am »
Yes, rotating the yoke would indeed rotate the whole image.  I wasn't completely sure what distortion you were referring to.

Take a look at this manual for the Panasonic TR-60S1A monitor:

  https://elektrotanya.com/panasonic_tr-60s1a_chassis_y21_sm.pdf/download.html

If you have this monitor or something similar, the manual describes some additional tweaking magnets that may help the distortion.

It doesn't seem to me like a capacitor problem, but I'm interested if you don't mind posting the fix when you figure it out.
 

Offline veedub565

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Re: 8590 series CRT slant
« Reply #4 on: July 06, 2021, 05:08:04 pm »
Thanks Mark, I've decided to leave it alone. Tweaking the yoke and/or magnets might or might not sort it. Or it might make things worse by me messing with it. I did replace some of the caps in the deflection coil circuit just in case there was an s correction problem. didn't make any difference.

 


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