Discoloration keeps coming back daily at bottom right corner of the screen

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keropi
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by keropi »

I have missed that suggestion, I will try it and report back. I tried asking about a replacement thermistor at a shop that carries many vintage parts BUT they carry them via replacement codes found in datasheets. Since a 8060S service manual is nowhere to be found I have no idea how to ask about it and neither the store owner knows...
I have even thought of replacing the coil and use a matching thermistor for it, would that be a good solution if it turns out to be the issue?

edit:
I have found some 9ohm thermistors: http://www.ebay.co.uk/itm/371973518762
here is the datasheet: http://www.nscn.com.cn/new_pdf/dip/remin/MZ7.pdf

Do you think I can try them? The 7ohm version isn't available ...
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Asayuki
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by Asayuki »

The one you found on ebay looks comparable technically-speaking.

With regard to changing the whole ptc + coil thing, if you can find a mechanically fitting replacement then why not? Just be careful to the usual stuff and maybe try the new one from the outside first, before you go through all the work.
My 15kHz cabinet Peplos will never power up, with any item, and I am quite proud of that.
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keropi
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by keropi »

I will have to see how I proceed with this since I also discovered some geometry issues. Good thinking on testing the coil from the outside, thanks for that :)
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keropi
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by keropi »

I gave up on this for the moment. Further investigation requires messing with the deflection coil - haven't decided if I will do it or no.

I also found what the original PTC thermistor is , it's a dual PTC Murata 22ohm one. (I measured some posistors that I know their model numbers and verified through datasheets so I was able to easily determine how to measure the original one)
I tested with another posistor+matching coil : the discoloration is still there.

Been thinking I should just reduce the viewable area and exclude the corner, it's not that bad of a compromise... :lol:
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by cools »

Disable it, manual degauss when required
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keropi
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by keropi »

but the degauss coil/posistor is not the issue cools : coil or no coil or a different coil/posistor that damned corner will always revert to being a party pooper :lol: :lol: :lol:

(the deflection coil is the conical one behind the tube, nothing to do with the degaus coil)
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by Asayuki »

Do I understand your post correctly? You just implied that the degaussing either does not work at all, or it is having no effect.
Are you sure the coil gets powered to begin with? You could check the continuity of all of the few involved traces from power input up to the coil connector... (with power disconnected of course).

edit: traces at times can get affected by micro-fractures which are not visible to the naked eye. This tends to happen expecially around soldered pads.
My 15kHz cabinet Peplos will never power up, with any item, and I am quite proud of that.
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keropi
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by keropi »

Let me break it down a bit :

- original posistor + original coil = no effect on that little corner
- matching posistor + 14ohm coil = no effect on that little corner

the only thing that gets rid of the discoloration temporary is using an external degauss coil (=stronger effect?)

I have tested the psu for cracks/etc but I did not find anything weird. I even connected an old-style light bulb instead of a coil and it does light for a sec in each power-on :awe:

I took some PSU photos just in case you can see anything weird that I missed (the posistor onboard is not the original but the one that works with the 14ohm coil)

Image Image

Image Image

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Asayuki
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by Asayuki »

Should it have been a slight misplacement or damage of the yoke or purity rings block, you wouldn't be able to fix it with the external degausser. Therefore I'm clueless. :-o
The only thing that comes to my mind at this point is a bizarre, wild and unlikely theory involving the internal metal pixel grid of the tube and electrostatic attraction induced by the electromagnetic field of the external degausser; this would imply an internal physical defect of the tube, so please ignore my overconvoluted blabbering. :shifty:
My 15kHz cabinet Peplos will never power up, with any item, and I am quite proud of that.
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keropi
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by keropi »

Yes it is quite possible the tube has the issue that's why I am not that interested to mess with the deflection coil. I'll cut my loses and just shrink the viewing area a bit :awe:
thanks for all the input Asayuki and cools , appreciate it! :)
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by PrincessPrinPrin »

Since the degaussing coil is not visible in the pic on page 1 it must be the type that goes around the faceplate, i.e. sits on the rimband. I would try and replace it with a type that sits on the funnel and see if the different coil arrangement has any effect on the corner. If not it means that the mask has been deformed so much that it can only be degaussed by a stronger external coil.
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keropi
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by keropi »

yes exactly, the original coil sits in the faceplate, around the tube. I have another 7ohm smaller coil I can test, I understand what you mean. I'll report once I do that.
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keropi
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Re: Discoloration keeps coming back daily at bottom right corner of the screen

Post by keropi »

Tried it, didn't help. I've made up my mind and put the monitor back - I'll reduce the view area and live with it :lol:
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