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Jx Canal

Atari 800XL dies after UAV mod

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Good day all

this is my first post and hopefully it’s not redundant. So I Had my faithful 800xl running smooth but was in dire need of decent graphics. This site was a great source of info and I found/ordered the UAV. I did the install. Not too tricky. However, since then I have not been able to get her to boot. Using this gorum

i did some testing with differing results. RAM hasn’t changed, tried no bios/bios, cart boot etc... I’ve seen a blue screen, a screen with vertical lines. Sadly though I have yet to hear the warm

bleeps of the xl booting/loading floppy. What am i misding?

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do you have a star raiders cartridge you can try? it bypasses the OS ROM so if the game boots, the OS ROM is defective

also, if your chips are socketed, try removing and re-inserting them in case of a bad contact

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So details of your installation including photos would help. If the 800XL was fully socketed (some are) you remove the 4050 hex buffer chip in the video circuit and put the UAV into place, solder the Color signal wire and the wires to the video DIN jack and you're done. Nothing in this procedure should prevent the machine from booting, and if you remove the UAV and re-install the UAV, you should get stock composite video back.  If your 800XL has the 4050 soldered, you typically would desolder the 4050, install a socket, install the UAV into that and proceed as the above. 

 

None of that SHOULD affect the general functionality of the machine - you can boot an Atari with no video or audio output connected at all and it will happily run forever. So photos of what you did and what you're seeing on-screen are really necessary to offer more help.

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Thank you for the replies people! I will try star raiders first. One thing with UAV is it kills the RF. I didn’t use/have a connector for the 5 pin until I got the UAV. Since I was soldering to the output port where the composite would be, I worry that’s where I could’ve erred. The RF being disabled I have no 100% working go to.  Will take photos. The UAV was socketed on install. Since the mod, as noted I get no red light or drive action. Novice here! Could the metal shield not being used ground the board out? Also, could Hair line scratches on the top side of the board from soldering cause issues? Thanks in advance 

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Photos of your installation might help diagnose any issues. 

 

As I said above, there's nothing in the UAV installation process that should prevent the machine from booting up. The computer should run even if you don't get video out. So if you're not getting the red power LED, then something else is going on. Don't worry about the RF shielding - it's not necessary for the machine at all. Many folks remove it entirely for A/V modded computers and consoles, and certainly when we have the naked boards on our workbenches for testing or modifications, we don't use the RF shield.

 

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14 hours ago, Jx Canal said:

One thing with UAV is it kills the RF ... The RF being disabled I have no 100% working go.

 

I was able to keep RF functional as well as the UAV by soldering a socket on top of the 4050 (which was also originally socketed), and plugging the UAV into that. It made for a pretty high stack, but it works... (definitely does not fit inside the shield, unless you cut a hole) It might be compromising the video quality a bit, but it's still better than 130XE S-Video.

 

@Jx Canal you mentioned you saw no difference in behaviour with the OS ROM removed? Do you by chance have another 600XL or 800XL that you could test by swapping IC's to? It's possible a static discharge has damaged an IC. What type of power supply are you using? One type the "ingot" is known to fail with voltage high enough to damage components. If you were soldering, make sure any flux residue is cleaned up. 

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This is an interesting thread.  I also just installed the UAV and finally got it working properly on my Rev D 800XL (Display quality looks amazing now)...  However, I am having intermittent booting on the Atari now.  Sometimes it boots up fine and into Basic.  Other times it mostly just crashes on boot up and the screen freezes or goes black or displays junk.  Cartridges all work fine.

Could this be a problem with the ROMS (ROM check says they OK), or an issue the UAV is causing?  I'm starting to wonder what I fried on my motherboard during my UAV install.  Anybody else had this issue?  

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Photos of peoples’ work would help. Again, for at least the third time, the UAV should have zero impact on the general functioning of the computer. The system can operate completely fine with no video output, and the UAV picks up all its signals from “downstream” of the IC’s that cause the computer to run and operate. It uses LUM, SYNC and COL signals from the GTIA and merely intercepts them before they run through the stock Atari video components.

 

If your system doesn’t work after you’ve installed the UAV, you’ve shorted something or damaged the motherboard in some way.

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