bushnrvn Posted February 4 Share Posted February 4 (edited) Hoping the community can help point me in the right direction. First, the machine displays non-text garbage almost like a psychedelic oscilloscope when the keyboard is plugged in. When the keyboard is unplugged from the main board, the machine boots to BASIC and loads carts. Second, the RF signal is extremely noisy. I expect some noise, I grew up with RF, but this is pretty bad. Odder still, it seems that moving the machine, putting a small amount of pressure on the RF out connector at the computer, and pressing slightly on the RF shield all seem to very marginally improve the RF signal. I'm thinking there’s a short somewhere in the way to the RF modulator and maybe the gunk on the mylar keyboard cable are causing issues. Thoughts? Edited February 4 by bushnrvn Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted February 4 Share Posted February 4 (edited) I'd try the Atari RF cable with the taroid coils and make sure the shields were on and the select different channels on the Atari RF mod and display a few times, it the tuner has frequency control you could try dialing it in. more things to do but I'd start there. Then we move on to transistors, 4050, and work our way down. add in the monitor jack components and the socket etc and see what they produce. If you have a scope et al grab the FSM, SAMS, etc and dig in. Edited February 4 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
bushnrvn Posted February 4 Author Share Posted February 4 Yeah this is the path. Good advice. I was hoping for bit of hive knowledge along the lines of "oh yeah this is a known issue" but c'est la vie 🙂 Quote Link to comment Share on other sites More sharing options...
TZJB Posted February 4 Share Posted February 4 9 hours ago, bushnrvn said: Hoping the community can help point me in the right direction. First, the machine displays non-text garbage almost like a psychedelic oscilloscope when the keyboard is plugged in. When the keyboard is unplugged from the main board, the machine boots to BASIC and loads carts. Second, the RF signal is extremely noisy. I expect some noise, I grew up with RF, but this is pretty bad. Odder still, it seems that moving the machine, putting a small amount of pressure on the RF out connector at the computer, and pressing slightly on the RF shield all seem to very marginally improve the RF signal. I'm thinking there’s a short somewhere in the way to the RF modulator and maybe the gunk on the mylar keyboard cable are causing issues. Thoughts? You are not giving much away here. I presume this to be a NTSC 600XL as you have a channel switch? There is obviously lots of noise in the picture. Has the TV picture been proven reliable with another device? What power supply are you using as there may be noise from the 5 Volt PSU? Is this voltage within range? When you attach the keyboard, the chassis of the keyboard should be tied to the 600XL ground as it would be if the screening were attached. The problem may be due to the modulator itself so definitely do what @_The Doctor__ suggested and switch to composite or Svideo output by supplying the monitor out components, which would always be the way forward. Incidentally if the device has socketed chips, check that oxidisation to the pins has not occured. Best of luck. Quote Link to comment Share on other sites More sharing options...
reifsnyderb Posted February 4 Share Posted February 4 The two issues I've seen that can cause this have been the channel select switch and/or the TV/Computer switch box that goes from the computer to the TV. 1 Quote Link to comment Share on other sites More sharing options...
bushnrvn Posted February 4 Author Share Posted February 4 3 hours ago, TZJB said: You are not giving much away here. I presume this to be a NTSC 600XL as you have a channel switch? There is obviously lots of noise in the picture. Has the TV picture been proven reliable with another device? What power supply are you using as there may be noise from the 5 Volt PSU? Is this voltage within range? When you attach the keyboard, the chassis of the keyboard should be tied to the 600XL ground as it would be if the screening were attached. The problem may be due to the modulator itself so definitely do what @_The Doctor__ suggested and switch to composite or Svideo output by supplying the monitor out components, which would always be the way forward. Incidentally if the device has socketed chips, check that oxidisation to the pins has not occured. Best of luck. NTSC 600XL TV works great with everything else. PSU is the big white (yellow these days) brick, but I have ordered a replacement from TBA. Keyboard is tied to ground, but I noticed the solder blob that connects the main board ground to the keyboard is split right down the middle. The wire is still soldered securely, but I'll redo this just in case. I do suspect this is a grounding issue - pressing the metal shield into contact with the RF modulator (not even firmly, just enough to contact) improves picture quality considerably. Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted February 4 Share Posted February 4 The white brick is easily re-build-able and is one of my favorite supplies. Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted February 4 Share Posted February 4 (edited) can of tuner cleaner if it's the channel switch or antennae switch box. Share all the details and connections. Edited February 4 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
bushnrvn Posted February 6 Author Share Posted February 6 Update. I disassembled the keyboard and it is apparent that at some point in the past four decades, someone spilled something all over the keyboard. The mylar matrix is toast, covered in a crystalline brown gunk. With the mylar matrix removed from the keyboard assembly, I gave it a good scrubbing in the hopes that cleaning some of the gunk off the traces would resolve the weird power\crash issue. This did the trick - the machine now boots with the keyboard plugged in, but of course, several of the keys are dead due to corroded or broken traces on the mylar. I know there are replacements out there, and that is what I will have to do, but would appreciate a recommendation as the only sources I've found are in Australia or the UK. I am in the US. Overall, looking pretty good for this little machine so far. 1 Quote Link to comment Share on other sites More sharing options...
+scorpio_ny Posted February 6 Share Posted February 6 16 minutes ago, bushnrvn said: I know there are replacements out there, and that is what I will have to do, but would appreciate a recommendation as the only sources I've found are in Australia or the UK. I am in the US. 8Bitclassics sells them and are located in the US. Here is a link the keyboard mylar: https://www.8bitclassics.com/product/retronics-atari-600xl-800xl-keyboard-mylar-replacement/ 1 Quote Link to comment Share on other sites More sharing options...
bushnrvn Posted February 8 Author Share Posted February 8 On 2/6/2024 at 12:04 AM, scorpio_ny said: 8Bitclassics sells them and are located in the US. Here is a link the keyboard mylar: https://www.8bitclassics.com/product/retronics-atari-600xl-800xl-keyboard-mylar-replacement/ Ordered. Thank you! Quote Link to comment Share on other sites More sharing options...
+scorpio_ny Posted February 9 Share Posted February 9 6 hours ago, bushnrvn said: Ordered. Thank you! Great! Glad to help out! 1 Quote Link to comment Share on other sites More sharing options...
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