mikro Posted October 29, 2016 Share Posted October 29, 2016 Hi guys, it has been a while since I had something to do with an 8-bit Atari. However, while collecting a lot of STs I've noticed there's an XEGS thrown in. I was quite happy to realise that because having an XEGS was a secret dream of mine when I used my little Atari. Unfortunately, it doesn't work. When I switch it on, I see only this: Once I managed to see a yellow-ish screen (with keyboard unattached), I assume that was because the built-in game was about to load but I haven't been able to reproduce it. The PCB looks very good: no leaked capacitors, no suspicious places on the PCB. If I press RESET, nothing visible (on that screen anyway) happens so I think the failure occurs sometime in an early stage. The green LED is on, so the PSU should be working as well. I can't hear any audio either, so it's not an video output problem. Any hints what to check? 1 Quote Link to comment Share on other sites More sharing options...
Rybags Posted October 29, 2016 Share Posted October 29, 2016 (edited) Power on holding Select. That will reverse the game/Basic behaviour, ie without keyboard attached should attempt to start with Basic. In the game mode, you might want to press Start once it's been powered on for about 5 seconds, you should get the game audio if it's working. The most basic sign of life from an Atari though - when you power it on or press Reset, you should get the click through the audio. But these signs are only good if the machine is actually operating. What you can do next depends on what diagnosis equipment you have and whether you have the skill to desolder and solder stuff. A common failure source on XE is the RAM chips especially if they're the MT brand. Leaving it powered on a few minutes then finger test the Ram, and other major chips can sometimes pick up suspects. The Ram on the XEGS is the 2 21464 chips in the bottom left corner next to the 14187 KHz clock crystal. Edited October 29, 2016 by Rybags 1 Quote Link to comment Share on other sites More sharing options...
Paul Westphal Posted October 30, 2016 Share Posted October 30, 2016 Turn on the system for a minute. Touch the chips to see which ones are hot. That's the culprit(s). Most likely it's the ram- lower left hand bottom ( two chips ). Quote Link to comment Share on other sites More sharing options...
mikro Posted October 30, 2016 Author Share Posted October 30, 2016 Guys, that was a pretty good advice. The chips indeed are quite hot. Is the solution as simple as desolder these and replace them with new ones? Quote Link to comment Share on other sites More sharing options...
Rybags Posted October 30, 2016 Share Posted October 30, 2016 Which chips? For the Ram especially it's a good idea to put sockets in to make future replacement a lot easier. It's also a good idea to check your power supply. Preferable method would be with the computer open and turned on, it shouldn't be too far over 5 Volts. A common cause of failed internals is with power supplies that get old and start overvolting. Quote Link to comment Share on other sites More sharing options...
mikro Posted November 1, 2016 Author Share Posted November 1, 2016 OK, so I've de-soldered the memory chips and ordered new ones. While doing that, I realised that's it's maybe good idea to replace also the two resistors close to each chip, however I'm not sure how to identify / buy them? There's "cgw 224 z5j 8742" printed on each of them but I'm not sure which number use to ID. At least I hope it's a common part. Anyone knows? Quote Link to comment Share on other sites More sharing options...
Rybags Posted November 1, 2016 Share Posted November 1, 2016 C20 and C21 to the left of the Ram chips are capacitors. I'd just leave them be. With the XE some components aren't what they seem. There are capacitors in resistor packaging and I believe some components that look like clear diodes but are something else. The clue is usually in the labelling on the board, e.g. C, R for capacitors and resistors, L for inductors, U for ICs. Quote Link to comment Share on other sites More sharing options...
mikro Posted November 1, 2016 Author Share Posted November 1, 2016 (edited) Thank you Rybags, I'll report back after I'm done. And you're right, they are capacitors, 220 nF if I'm not mistaken. EDIT: Btw, I've noticed that close to the capacitors there's a couple of holes. One must be very careful not to mistake them with the holes meant for the capacitors, any idea what they are, seemingly leading nowhere? Edited November 1, 2016 by mikro Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted November 1, 2016 Share Posted November 1, 2016 I think they're just vias connecting the top and bottom ground planes. Quote Link to comment Share on other sites More sharing options...
shoestring Posted November 1, 2016 Share Posted November 1, 2016 These are decoupling capacitors, their main purpose is to filter out high frequency noise. The signal diode looking things are capacitors too, I've seen them mixed up with other types in the dram circuit . I guess they use everything they get their hands on and leave nothing to waste Quote Link to comment Share on other sites More sharing options...
mikro Posted November 17, 2016 Author Share Posted November 17, 2016 OK, memory chips received, sockets soldered and ... still doesn't work. It even feels like the chips are getting more hotter than before (maybe because they still work). Screen output is different, it looks like it's about to set the resolution and everything correctly but it doesn't: The sockets and memory seem to be OK: Any idea what to try next? Quote Link to comment Share on other sites More sharing options...
shoestring Posted November 19, 2016 Share Posted November 19, 2016 (edited) Check reset circuit first. You said nothing happens when you press reset but look & listen carefully, there should be a pop sound or some indication on the screen. You really need at least a logic probe to see that. And it should be a transition from low to high ( and it should stay high ) on the RST pin of the 555 timer or from Sally. With reset broken your CPU just sits there with its address outputs stuck high and nothing at all happens on the screen. If reset is good and CPU address outputs don't toggle then you probably have a bad CPU or clock dividers. With the latter case, it's time to check Freddie and the address decoder as well. Edited November 19, 2016 by shoestring Quote Link to comment Share on other sites More sharing options...
mikro Posted November 25, 2016 Author Share Posted November 25, 2016 (edited) I've just re-read the whole thread and I've noticed that Rybags mentioned one more important advice -- to check the PSU. And guess what, it really seems broken. When powered on, plugged into the XEGS, I can get stable voltage of ... one volt. What is rather bad as you mention it should be five. Do you think this could cause some internal damage or I just resoldered the memory chips for nothing and need only to replace the PSU? Edited November 25, 2016 by mikro Quote Link to comment Share on other sites More sharing options...
Matej Posted November 25, 2016 Share Posted November 25, 2016 (edited) Use heatsink: http://eu.mouser.com/Thermal-Management/Heat-Sinks/_/N-5gg0 + Use this PC tuning GLUE (buy EPOXY not thermal paste): http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm NEW PSU replace (tip from RASTER): http://www.conrad.com/ce/en/product/514406/Dehner-Elektronik----SYS-1308-1505-W2E-EURO-BlisterSocket-Adapter- But that is normal EURO socket adapter search similar for AU... BTW when you will be at home (BA) I will give you extra XEGS keyboard!!! Edited November 25, 2016 by Matej Quote Link to comment Share on other sites More sharing options...
re-atari Posted November 25, 2016 Share Posted November 25, 2016 (edited) I've just re-read the whole thread and I've noticed that Rybags mentioned one more important advice -- to check the PSU. And guess what, it really seems broken. When powered on, plugged into the XEGS, I can get stable voltage of ... one volt. What is rather bad as you mention it should be five. Do you think this could cause some internal damage or I just resoldered the memory chips for nothing and need only to replace the PSU? Before you put the PSU in the dumpster, check if it outputs the nominal 5 Volts when it's not connected to the console. If there's a short somewhere on the mainboard, it will draw down the voltage the PSU can deliver. There is a PSU type known for failing, that when doing so, delivers a way too high voltage, killing several IC's (like the DRAM's and Freddie) in the process. This PSU is known as 'Ingot'. There are already a few threads on AtariAge on the subject of PSU's, you should be able to find them using the search function. If the PSU turns out to be toast and you're handy with electronics and a soldering iron, you could turn an old USB phone charger into a PSU for testing. Just use the cable with A8 Din-connector from the old PSU. Do make sure the charger delivers 1 Amp and 5 Volts. re-atari Edited November 25, 2016 by re-atari Quote Link to comment Share on other sites More sharing options...
mikro Posted November 28, 2016 Author Share Posted November 28, 2016 Guys, today I was born again. Firstly, let me show you how dumb I am. It all started with the black screen. Following your advice, I ordered the memory chips. Four, as well as four sockets, since my soldering skills are very questionable at best. So I got the sockets and chips, managed to desolder and solder everything, incl. the capacitors, just to be on the safe side. Power on -- same result, even hotter chips. As you know, my "diagnosis" was too weak PSU. As it turned out, it was the PSU, right, but -- I was measuring wrong voltage, AC instead of DC. As soon as I realised that -- 11V! Holy s..t! So I was pumping 11V to the poor XEGS all the time!!! Took out the memory chips (thank you sockets!), put the last two in (oh my, how happy I was to realise I still have two more!), bought a new 5V/2A PSU, resoldered the wires (and made damn sure I got the polarity right) and ... ... boom! Couldn't believe my eyes. Funny thing is that I wanted to give this little guy just a quick brush up, test it and sell it as my 8-bit times are well over (Falcon coder speaking here...). But after all this, I've become emotionally attached to it. I even got few cartridges! Anyway, thank you all for valuable hints, as you can see, they did help me a lot. 3 Quote Link to comment Share on other sites More sharing options...
Andromeda Stardust Posted November 28, 2016 Share Posted November 28, 2016 11v! Geeze... Quote Link to comment Share on other sites More sharing options...
Matej Posted November 28, 2016 Share Posted November 28, 2016 (edited) Dont sell it XEGS are rare stuff! More rare than A130XE... Also there is PC keyboard interface: http://ataribits.weebly.com/transkey-ii.html Or http://ataribits.weebly.com/tk-ii-stereo.html Also Raster Ramcart http://raster.infos.cz/atari/hw/ramcart/ramcart.htm So you will be able to play XEGS games+RAMdisk... Edited November 28, 2016 by Matej Quote Link to comment Share on other sites More sharing options...
Kyle22 Posted December 1, 2016 Share Posted December 1, 2016 Put a U1Meg in it and get an SIDE2 cart. Enjoy your hard drive and SpartaDOS-X. The ATR Loader is AWESOME! To finish it off, get the Ultimate SD MultiCart. I have a WiFi SD card in mine. You can have 99.9% of the entire Atari library at your fingertips. 1 Quote Link to comment Share on other sites More sharing options...
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