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Colour Classic screen issue

A

alasdairrr

6502
Hi All,

I recently acquired a non-working Colour Classic, which after a full recap of the main board came back to life (with a working HDD, woohoo!).

Unfortunately it seems there is a dark splodge across the centre of the screen.

I’ve replaced some components on the Analogue Board that had signs of burn marks around them (DL21/DL22 Zener diodes - 1N4724A 1W 3V-100V, DP6 Schottky Rectifier - MBr1045 10A 45v, RP15 220ohm resister), but this has made no difference.

I am wondering if this is sunburn and that the screen had been left in the sun. Is this likely the case or could there be an alternative reason?

I’ve attached some photos (was quite hard to capture it with the camera)

Many thanks in advance,

Alasdair
 

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Sunlight shouldn't harm CRTs. That looks like the CRT got partially magnetized, and the internal degauss coil either isn't working or isn't strong enough to fix it (or it is strong enough but it will take multiple cold power-ups to go away). On a cold power-up does it make a typical momentary loud hum/buzz?
 
Arbee said:
Sunlight shouldn't harm CRTs. That looks like the CRT got partially magnetized, and the internal degauss coil either isn't working or isn't strong enough to fix it (or it is strong enough but it will take multiple cold power-ups to go away). On a cold power-up does it make a typical momentary loud hum/buzz?
Click to expand...
A thump (a deep, quick "doop" noise) or something similar - I'm not sure how loud it is on a 10" CRT, it's not super loud on a 9" Mac.
 
If you somehow get it fixed, please post it here. I'm in the same boat you are in:

Color Classic Screen / Dim Spot

I am the fortunate owner of a Color Classic. However, it has a screen issue. Basically, there is a big chunk of the screen that appears a bit dimmer than the rest. I've tried playing with the brightness, tweaking the (exposed) CRT settings, and even started just recapping the analog board. The...
68kmla.org 68kmla.org
 
Just a heads up, I fixed my issue (which looked exactly like what you had). Yes, it goes away with degaussing. Look at my above post for specifics.
 
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