BraddW Posted November 8, 2006 Share Posted November 8, 2006 Hello everyone. I just bought a "non-working" 800XL off of ebay. I got it today, and plugged it in to see if anything at all worked on it. At first all I got was a white screen and no sound. The computer would not boot up. I took it apart to see if there was any obvious signs of damage. There were none. It did look like the RF signal box was replaced though. Much to my surprise, when I tried to boot the computer without the RF shields on or keyboard attached, it worked just fine. I then installed a 100 ohm resister and wire connection for the missing chroma signal, and tried to boot again. Once again it worked fine and this time in full color. Next, I reassembled the computer and tried to boot it, and it again diplayed a white screen with no boot. I disconnected the keyboard accidentally with the power still on, and the computer then proceeded to boot just fine. I took the keyboard from my old faithful 800XL and put it into this new one, and it worked. So to finally get to my question, does anyone have any idea what might be wrong with this keyboard? I have never heard of a keyboard preventing a computer from booting before. Is it possible that this keyboard could be repaired, or do I most probably need a new one? Thanks in adavnce for any help anyone can provide. Bradd Quote Link to comment Share on other sites More sharing options...
Urchlay Posted November 8, 2006 Share Posted November 8, 2006 does anyone have any idea what might be wrong with this keyboard? All I can think of is a short, causing the keyboard to draw way too much current, starving the rest of the machine... but you could check this, you have a known good keyboard, could use an ohmmeter to see whether the bad one has a short somewhere the good one doesn't. Hm, one other possibility... doesn't the 800XL keyboard have a multiplexer or two, little ICs? Maybe those are bad, forcing the IRQ line to stay on all the time? (I have a software guy's view of the hardware, somebody who actually knows what they're talking about will surely shoot that idea down...) Quote Link to comment Share on other sites More sharing options...
Beetle Posted November 8, 2006 Share Posted November 8, 2006 No, the multeplexers are on the 800XL mainboard. you could check this, you have a known good keyboard, could use an ohmmeter to see whether the bad one has a short somewhere the good one doesn't. I'd suggest you do that, too. Regards, Beetle Quote Link to comment Share on other sites More sharing options...
BraddW Posted November 8, 2006 Author Share Posted November 8, 2006 No, the multeplexers are on the 800XL mainboard. you could check this, you have a known good keyboard, could use an ohmmeter to see whether the bad one has a short somewhere the good one doesn't. I'd suggest you do that, too. Regards, Beetle Thank you both for the suggestion. I will give that a try. Bradd Quote Link to comment Share on other sites More sharing options...
BraddW Posted November 8, 2006 Author Share Posted November 8, 2006 Hello again, I am going to attempt to find the suspected short in my 800Xl keyboard tonight. I just had an idea, and wanted to check to see if you guys feel this is a sound course of action. I was thinking that I could put small pieces of tape over the ends of the traces(one at a time) of the keyboard connector, and plug it in that way. That could possibly allow the machine to boot when the trace that is shorted is covered by tape and thus insulated. That would at least give me an idea of where to start looking to find the short. Does this sound reasonable, or am I way out in left field? Also, how is it that the keyboard can short in the first place? Do the traces on the mylar film somehow come in contact with one another? I've never had a problem like this before, so this is all quite new to me. Any help is greatly appreciated! Thanks! Bradd Quote Link to comment Share on other sites More sharing options...
tjlazer Posted November 8, 2006 Share Posted November 8, 2006 "I then installed a 100 ohm resister and wire connection for the missing chroma signal" What was the mod for the chroma on the 800XL? I thought it was just a wire that needs to be soldered. Quote Link to comment Share on other sites More sharing options...
BraddW Posted November 8, 2006 Author Share Posted November 8, 2006 "I then installed a 100 ohm resister and wire connection for the missing chroma signal" What was the mod for the chroma on the 800XL? I thought it was just a wire that needs to be soldered. Its part of the super video mod that can be done to 8bits. I never tried it, but I would assume that if you just solder in a wire you would restore the missing chroma signal. However, since I had the instructions for the entire super video mod, I followed those instructions which called for a 100 ohm resistor to be soldered in along with the wire. I would ask someone with a little more knowledge than myself why that resistor needs to or does not need to be there. I have never tried it without, but I know for sure that it works with the resistor there. I would be careful doing it without the resistor though. It could possibly allow to much current to pass through and damage something. As I said, I could be wrong here, but whenever I deal with electronics I always like to err on the side of too much resistance instead of too little. Bradd Quote Link to comment Share on other sites More sharing options...
Almost Rice Posted November 8, 2006 Share Posted November 8, 2006 "I then installed a 100 ohm resister and wire connection for the missing chroma signal" What was the mod for the chroma on the 800XL? I thought it was just a wire that needs to be soldered. Its the same. I have seen some with just the wire and some put a 100 Ohm resistor, but they both go to the same location on the board. I just did it last night with a 800xl from zektor800. Quote Link to comment Share on other sites More sharing options...
BraddW Posted November 9, 2006 Author Share Posted November 9, 2006 Good news. The problem has been fixed. I took the keyboard apart, and as I was doing so, a very small metal wire that looked like a resistor lead fell out. I am guessing that that is what was causing the short in my keyboard. I gave it a good cleaning and reassembled, and it now works perfectly. Thanks very much for the help. Bradd Quote Link to comment Share on other sites More sharing options...
Urchlay Posted November 9, 2006 Share Posted November 9, 2006 Its the same. I have seen some with just the wire and some put a 100 Ohm resistor, but they both go to the same location on the board. I just did it last night with a 800xl from zektor800. Is there a similar spot on the 1200XL board, to get a chroma signal? I've searched, but I keep finding really complex mods that involve lots of parts (Clearpic 2002 mod, for one). I'm just wondering if it's possible to get chroma by soldering one wire (or one resistor, maybe)? Quote Link to comment Share on other sites More sharing options...
Gunstar Posted November 9, 2006 Share Posted November 9, 2006 "I then installed a 100 ohm resister and wire connection for the missing chroma signal" What was the mod for the chroma on the 800XL? I thought it was just a wire that needs to be soldered. Its the same. I have seen some with just the wire and some put a 100 Ohm resistor, but they both go to the same location on the board. I just did it last night with a 800xl from zektor800. I would think the resister is just there to protect against any possible surge in the chroma line, since 100 Ohm is so small a resister anyway. It's just for protection and consistancy, but you could probably get bye without it and never have a problem. Maybe the chroma signal is a bit stronger than the lumina and the 100 Ohm resister balances them out a bit better. I'd have to test it to see. I did the full Super video mod to my XL and I'm about to just boost the chroma signal on my XE instead of doing the full mod to it, becuase the s-video output is sharp enough for me already, but the color isn't strong enough. Quote Link to comment Share on other sites More sharing options...
Almost Rice Posted November 9, 2006 Share Posted November 9, 2006 Is there a similar spot on the 1200XL board, to get a chroma signal? I just did it to my 1200xl. I put a wire from R44(does not matter which side) to Pin 5 of the monitor port. Using Q7 was too bright. The 1200xl really needs those mods. The screen is still fuzzy to me. Chroma for the 800xl I had was a lot clearer. Quote Link to comment Share on other sites More sharing options...
Gunstar Posted November 9, 2006 Share Posted November 9, 2006 I did those same mods at first myself, but was also unhappy with the fuzziness of the picture compared to my XE in S-video, so I went back and did the entire Super-video mod. Everything looks great now on my XL. Quote Link to comment Share on other sites More sharing options...
Urchlay Posted November 9, 2006 Share Posted November 9, 2006 I just did it to my 1200xl. I put a wire from R44(does not matter which side) to Pin 5 of the monitor port. Using Q7 was too bright. The 1200xl really needs those mods. The screen is still fuzzy to me. Chroma for the 800xl I had was a lot clearer. Thanks. I'll try that over the weekend, see if it helps. I've got the 1200XL, an 800, and an XEGS. In composite, the 800 has the best picture (the XEGS is also really nice). Of the three, only the 800 supports S-video, and it's stunningly beautiful to me. The 1200XL looks like it's using RF when it's using composite, and it looks like total crap when it really is using RF. I remember another trick I used to do a long time ago with an 800XL. I made a composite video cable that had the luma also connected to the composite, which (if I remember right) gave a much nicer composite picture. I'll try that with the 1200XL, too... Probably I'll end up doing the real supervideo or clearpic mod, but at my level of soldering skill (not so high), it's an all-day project with a definite chance of failure. Quote Link to comment Share on other sites More sharing options...
zektor800 Posted November 10, 2006 Share Posted November 10, 2006 I just did it to my 1200xl. I put a wire from R44(does not matter which side) to Pin 5 of the monitor port. Using Q7 was too bright. The 1200xl really needs those mods. The screen is still fuzzy to me. Chroma for the 800xl I had was a lot clearer. Thanks. I'll try that over the weekend, see if it helps. I've got the 1200XL, an 800, and an XEGS. In composite, the 800 has the best picture (the XEGS is also really nice). Of the three, only the 800 supports S-video, and it's stunningly beautiful to me. The 1200XL looks like it's using RF when it's using composite, and it looks like total crap when it really is using RF. I remember another trick I used to do a long time ago with an 800XL. I made a composite video cable that had the luma also connected to the composite, which (if I remember right) gave a much nicer composite picture. I'll try that with the 1200XL, too... Probably I'll end up doing the real supervideo or clearpic mod, but at my level of soldering skill (not so high), it's an all-day project with a definite chance of failure. Funny you shoudl bring these points up, as I just started a thread on the XEGS and 800 video out. Yes, the 800 is incredible...and the XEGS is really nice as well. My soldering skills are sub-par as well...which is why I have yet to attempt the chroma mod on the 800XL. I can do it, but the fear of failure prevents me. I have everything hooked up and running like a champ right now, would not want to destroy that. Ehh...maybe one day when I become more confident. Quote Link to comment Share on other sites More sharing options...
tjlazer Posted November 13, 2006 Share Posted November 13, 2006 (edited) Funny you shoudl bring these points up, as I just started a thread on the XEGS and 800 video out. Yes, the 800 is incredible...and the XEGS is really nice as well. My soldering skills are sub-par as well...which is why I have yet to attempt the chroma mod on the 800XL. I can do it, but the fear of failure prevents me. I have everything hooked up and running like a champ right now, would not want to destroy that. Ehh...maybe one day when I become more confident. I actually did the chroma mod to two of my 800XLs and all I did was hook a wire frm Q5 to pin 5. Works nice! Looks amazing on my C=1702. http://aland.roarvgm.com/mods/32.html Edited November 13, 2006 by tjlazer Quote Link to comment Share on other sites More sharing options...
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