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hueyjones70

800XL disappearing objects

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I have an interesting problem with an 800XL. I was running Pole Position and after a collision, my car partially changed colors. The right side turned to light blue and the tires disappeared. After rebooting several times and observing the results it seems that a sharp change in direction such as running off the track and coming back on or a collision with another car or an object will cause the change. I tried switching out the 4050 chip and that had on effect. It occurs whether I am using composite video or luma/chroma. Has anyone else experienced a similar incident or does anyone have any suggestions concerning a fix.

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hmmm, did you try other copies, versions of Pole Position... if it were a hardware issue it normally would manifest in other titles and games as well

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I've seen the colours change when the power supply voltage is too low, ie 4.7V to 4.5V. (when I was using an insufficient USB power source). This also causes problems with SIDE2 reading CF cards. Have you checked your PSU voltage under load with system on?

 

I think the car and/or tires in Pole Position might be using PMG, which is generated by GTIA, not ANTIC, so maybe check if the GTIA is bad / swapping the GTIA chip with another machine

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I think the car and/or tires in Pole Position might be using PMG, which is generated by GTIA, not ANTIC, so maybe check if the GTIA is bad / swapping the GTIA chip with another machine

GTIA going flaky was my first thought too, followed by a possible power issue. But I’ve had two GTIA’s fail on me in different machines as well as a bad TIA in a 2600 (similar symptoms) so I’m primed to look for problems there.

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I have an interesting problem with an 800XL. I was running Pole Position and after a collision, my car partially changed colors. The right side turned to light blue and the tires disappeared. After rebooting several times and observing the results it seems that a sharp change in direction such as running off the track and coming back on or a collision with another car or an object will cause the change. I tried switching out the 4050 chip and that had on effect. It occurs whether I am using composite video or luma/chroma. Has anyone else experienced a similar incident or does anyone have any suggestions concerning a fix.

 

I have two GTIAs in my "defects drawer" with problems in collision detection. Both GTIAs will be detected bad by the SuperSALT diagnostic cartridge - you don´t need the external fixture for the GTIA test. One of the GTIAs is also detected bad by SysInfo utility.

 

So first test is SysInfo, then SuperSALT :)

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I have a different 800XL with a similar problem.  The computer boots, BASIC works.  Carts will not boot so I can't run supersalt.  Usually when I plug in a cart, I get nothing but a blank screen.  On a couple of occasions I got some random characters on the screen.  Star Raiders doesn't boot.

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I have reseated the ones that are socketed I am going to try and load a game from disk and if that works I may be able to eliminate a few options.

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Hmm maybe bad contact in the cart port?

 

Use a flashlight and inspect the cartridge port carefully for damaged fingers or debris. If all looks good, douse the contacts on a cartridge card edge with isopropyl alcohol, and quickly/repeatedly insert/remove it in the cartridge port to clean the connectors in the port.

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Thanks for the advice, I went one extra step and folded some emery paper and rubbed it up and down in the slot. Now everything works as it should.

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We were changing GTIA in friends 800XL, and one of the drawer GTIA we put in there did mad stuff with PMGs, so that would be my guess too.

Glad to see you solved it.

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