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130XE colors changing

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I have a 130XE that changes screen colors. This is not the color change that comes with a long period of screen idleness.  The shades of color change just a little every few seconds. The opening blue screen may take on a slight purple hue and then turn to a dark blue. I haven't timed it out but it seems to be about the same time interval on each shade. I wonder if it could be the color resistor. I have searched the forums and haven't found anywhere that anyone else has written about a similar problem.

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My 800XL does a similar thing.  It's not constant, and I haven't timed it out either, but I know what you mean.  On mine, it's everything going more green, then it snaps back to the original colors.

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The color pot may be dirty or developing cold solder joints. Touch up the contacts on the PCB with a soldering iron, then spray Deoxit or another cleaner into the pot and cycle it end to end a few times before allowing it to dry.  After that, check again. If that’s not it, there are a number of components in the circuit that might be bad or going bad that can cause voltage fluctuations and weird color effects. 

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Also: go to Atarimania and download a copy of the 130XE Sam’s Computerfacts. See p. 10 for detailed color troubleshooting information.  

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In XLs there is a circuit to produce 9.5v  or similar for the cadj circuit using what is called a charge pump with Phi1. 

Probably XEs have similar circuit. My guess is that there a capacitor of that circuit not working properly, so the circuit is producing an unstable voltage. 

Check the posted thread, and also the circuit schematics and check if the voltaje changes, and if those changes correlate with the changes in colors you see in the screen. 

 

Edited by manterola
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I have had this happen for all those reasons mentioned so far, at various times, in my experience, but I have also had this issue simply due to a damaged video cable or monitor DIN connector with cold solder points and/or tarnished pins. Bad contact through the pins or broken wires in a cable that change stuff like signal strength and resistance, can cause color issues like this, maybe from just the slight vibrations of typing on the keyboard or temperature changes, etc.

Edited by Gunstar
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13 hours ago, Gunstar said:

I have had this happen for all those reasons mentioned so far, at various times, in my experience, but I have also had this issue simply due to a damaged video cable or monitor DIN connector with cold solder points and/or tarnished pins. Bad contact through the pins or broken wires in a cable that change stuff like signal strength and resistance, can cause color issues like this, maybe from just the slight vibrations of typing on the keyboard or temperature changes, etc.

Not on my Atari, but had video issues, luckily I had a couple of ST's so had different cable, but same monitor, with the same issue

turned out to be a couple of broken solder joints where the SCART connector was soldered to the main board in the monitor., obviosly

broken due to remove/insert plug over many years

 

Just a quick re-solder and all fixed, so the same issue could be happening on the Atari socket.

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On 2/1/2020 at 10:15 AM, DrVenkman said:

The color pot may be dirty or developing cold solder joints. Touch up the contacts on the PCB with a soldering iron, then spray Deoxit or another cleaner into the pot and cycle it end to end a few times before allowing it to dry.  After that, check again. If that’s not it, there are a number of components in the circuit that might be bad or going bad that can cause voltage fluctuations and weird color effects. 

I did the Deoxit thing and the problem seems to have been eliminated, good call. Thanks.

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pesky debris in the component but well done for being tenacious!

new trimpots are v.affordable, maybe treat it to a new deluxe variant?

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