blacka013 Posted May 18, 2014 Share Posted May 18, 2014 Hi all, I recently purchased an Atari 800xe from ebay which is heavily modded. I came to use it this morning and would not boot up, the only life showing was the power led. It is modded with the following:- 1. 512K Memory Expansion2. A second Pokey chip enables real stereo sound3. Error Free GTIA Graphics controller4. Serial(Com) SIO2PC Interface connection5. Operating System switch6. Memory Select switch I have checked all the external connections and then substituted my old 800xl which worked. I have been back to the seller, suggested checking the connections, then asked if I knew anybody who was good with computers. Can anyone give me some advice fixing it please? Regards Quote Link to comment Share on other sites More sharing options...
blacka013 Posted May 19, 2014 Author Share Posted May 19, 2014 I have checked all the socketed chips are seated correctly, looked for any obvious signs but can't see any. The memory chips are MT 4067-12. The screen when powered up remains black with a no signal present showing on the TV, input selected correctly. I would have included a photo of the motherboard, but not sure how to insert it into the text. Regards Quote Link to comment Share on other sites More sharing options...
Rybags Posted May 19, 2014 Share Posted May 19, 2014 MT Ram is the bad stuff. But in this case I would guess probably something among those addons has come loose during shipping. I'd be checking the OS and memory mods first up. 1 Quote Link to comment Share on other sites More sharing options...
Keatah Posted May 20, 2014 Share Posted May 20, 2014 Agree! Push, poke, wiggle, and reseat all the add-on stuff. Examine solder joints for add-on stuff. Then we'll consider doing other stuff. Quote Link to comment Share on other sites More sharing options...
blacka013 Posted May 21, 2014 Author Share Posted May 21, 2014 Hi Rybags and Keatah, have followed your advice, still no joy. I then remembered my multimeter has a frequency selection, I tried this on my 800xl and the crystals are showing just under 4 MHz. I unplugged the upgrades from the 800xe motherboard and then tried this and I only get 23 KHz at best, so there is something definitely wrong in this area. Any suggestions on what to check next? Oh, can you explain how to upload images to the forum so you can see the board as I still can't get this to work? Regards Quote Link to comment Share on other sites More sharing options...
Keatah Posted May 21, 2014 Share Posted May 21, 2014 It is important to check your multimeter specification and be sure it is rated to handle the frequency of the crystal. If not, you'll get some arbitrarily low reading. Don't want to bark up the wrong tree. Quote Link to comment Share on other sites More sharing options...
blacka013 Posted May 21, 2014 Author Share Posted May 21, 2014 Th multimeter frequency will measure up to 15 MHz, the two crystal are 14.187578 and 4.433618 MHz. regards Quote Link to comment Share on other sites More sharing options...
blacka013 Posted May 23, 2014 Author Share Posted May 23, 2014 Ok, have completely de-modded the 800 xe and the fault remains, next stop ram change. Quote Link to comment Share on other sites More sharing options...
blacka013 Posted May 27, 2014 Author Share Posted May 27, 2014 I have removed the ram and decided to check the output from the crystal, still as before, so there must be something on the board still dragging them down. Does anyone have any suggestions. Thanks in anticipation Quote Link to comment Share on other sites More sharing options...
zylon Posted May 27, 2014 Share Posted May 27, 2014 (edited) Check your CO61618 IC. It's the 20-pin one just below the cart port. I just fixed one with a similar issue. It also had the MT ram. All 8 had to be replaced as they ran too hot to touch. That IC had me stumped until I used substitution with IC's from one of my 600xls Edited May 27, 2014 by zylon Quote Link to comment Share on other sites More sharing options...
blacka013 Posted June 8, 2014 Author Share Posted June 8, 2014 Finally, The problem was the Freddie chip, I substituted this from a dead 65xe I am also working on and it all works. Thanks for the help, it has been much appreciated. Now a dead 65 xe to resurrect. Quote Link to comment Share on other sites More sharing options...
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