bfollowell Posted June 2, 2020 Author Share Posted June 2, 2020 As far as your question about Sync, with SysCheck unattached, no, it doesn't stay low after a few seconds. It continues to pulse like the original pictures I showed for Sync. A longer stretch at high, then drops to more or less zero, then starts pulsing. Quote Link to comment Share on other sites More sharing options...
bfollowell Posted June 3, 2020 Author Share Posted June 3, 2020 I think I may have found something amiss. I've been stepping through the troubleshooting section of the SAMS 800XL service guide and I was looking good until I hit the clock and dividers section. I don't think I'm seeing a 3.58MHz waveform at the collector of Q8. I tells what to check if you don't have it or it doesn't look good, but I'd like to see the waveform someone is getting from a known good 800XL so that I can compare it to mine. Thanks. Quote Link to comment Share on other sites More sharing options...
Faicuai Posted June 3, 2020 Share Posted June 3, 2020 15 minutes ago, bfollowell said: I think I may have found something amiss. I've been stepping through the troubleshooting section of the SAMS 800XL service guide and I was looking good until I hit the clock and dividers section. I don't think I'm seeing a 3.58MHz waveform at the collector of Q8. I tells what to check if you don't have it or it doesn't look good, but I'd like to see the waveform someone is getting from a known good 800XL so that I can compare it to mine. Thanks. Just finished looking at this nested-spaghetti of testing and sampling, and something tells me that by starting in REVERSE order (at the end of the list) may lead you home, fast-and-safe. Good luck! Quote Link to comment Share on other sites More sharing options...
bfollowell Posted June 3, 2020 Author Share Posted June 3, 2020 I agree with you, but I'd still like to see an image of the waveform from the collector of Q8 from a good 800XL for reference. Quote Link to comment Share on other sites More sharing options...
+tf_hh Posted June 3, 2020 Share Posted June 3, 2020 21 hours ago, bfollowell said: With SysCheck attached, this is what I see for Refresh MMU pin 11 That´s absolute okay. What´s up with SYNC (CPU Pin 7)? Constantly toggling or remain low after some cycles (max. 10 seconds)? Quote Link to comment Share on other sites More sharing options...
+tf_hh Posted June 3, 2020 Share Posted June 3, 2020 19 hours ago, bfollowell said: As far as your question about Sync, with SysCheck unattached, no, it doesn't stay low after a few seconds. It continues to pulse like the original pictures I showed for Sync. A longer stretch at high, then drops to more or less zero, then starts pulsing. Okay. Then I´m pretty sure the main circuitry is working mostly fine, CPU can fetch commands, access to memory is fine, memory is working. I would focus on the video circuit. Maybe just the 4050 chip is gone? Quote Link to comment Share on other sites More sharing options...
+tf_hh Posted June 3, 2020 Share Posted June 3, 2020 16 minutes ago, bfollowell said: I agree with you, but I'd still like to see an image of the waveform from the collector of Q8 from a good 800XL for reference. That´s not needed, because you already checked PHI2 and PHI0 everywhere and it´s fine. PHI0 is simply OSC (3.5xx MHz) divided by 2. When PHI0 is fine, OSC must also be fine. 1 Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted June 3, 2020 Share Posted June 3, 2020 29 minutes ago, tf_hh said: Maybe just the 4050 chip is gone? That was my thought as well this morning as I looked at schematics but then a work crisis intervened and I never actually sent my reply. Anyway, can you the LUM outputs from the 4050 or better yet, just swap it with another one? Quote Link to comment Share on other sites More sharing options...
bfollowell Posted June 3, 2020 Author Share Posted June 3, 2020 I’ll have to check. I doubt I can just swap easily because, one, I probably don’t have another lying around, and two, I’m pretty sure it isn’t socketed on my board. I’ll check when I get home and get some replacement parts and sockets ordered. Thanks! Quote Link to comment Share on other sites More sharing options...
manterola Posted June 3, 2020 Share Posted June 3, 2020 (edited) What about booting with Start pressed , or typing something, and hear the sounds out of the speaker, or trying to boot a disk, etc? I don't think it is the cd4050, otherwise you will be able to observe other signs that would tell you that the computer is alive. Just because we discussing about the delay line in other topic (probably you already check that), maybe you can measure if the delay line is working properly by measuring the actual delays produced by it Edited June 3, 2020 by manterola Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted June 3, 2020 Share Posted June 3, 2020 4050 or perhaps flaky reset circuit or both.... Quote Link to comment Share on other sites More sharing options...
bfollowell Posted June 4, 2020 Author Share Posted June 4, 2020 OK, I'm planning to just order all of the LS chips, and sockets to go with them since those aren't socketed on my board. According to the SAMs manual, I have a discrepancy. U26 & U27 are multiplexers and are listed in the SAMS guide as 74LS158. However, my board has 74LS258 chips. I've looked and can't tell that there's any major difference between the two. I bought my 800XL brand new back in the day and it's never had any work done on it, so I'm assuming the 74LS258 chips are factory and that's what I'll replace with. What do you guys think? Quote Link to comment Share on other sites More sharing options...
Mclaneinc Posted June 4, 2020 Share Posted June 4, 2020 (edited) If 258's were on the board I'd deffo replace with the same, its an 'unlikely' botch from a factory... Data sheets show them both (158 & 258) as Quad 2 input multiplexors..And from a brief look the pin outs look the same. Edited June 4, 2020 by Mclaneinc Quote Link to comment Share on other sites More sharing options...
bfollowell Posted June 4, 2020 Author Share Posted June 4, 2020 (edited) That's what I was thinking too, but a second opinion is certainly appreciated. I'm going to socket all of my non-socketed chips, which is pretty much everything except for GTIA, ANTIC, SALLY, PIA, POKEY, and memory. I'm going to replace the existing sockets with better quality sockets, precision sockets like we used on the 1088XEL in the case of the big 40-pin chips and the BASIC and OS chips. This will make it easier to troubleshoot, modify, upgrade in the future. I'm also ordering replacements for all of the 74LS and CD40 stuff. If she's not running after this, I'll know it's something more basic like an open or a short that my old eyes just aren't catching. Thanks! Edited June 4, 2020 by bfollowell typo Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted June 4, 2020 Share Posted June 4, 2020 The 258/158 thing is discussed somewhere, either in a forum post or somewhere in a field service manual tech note. Ugh. I think the use of one over the other was a due to an Atari chip shortage from their suppliers and if your machine has one type, just keep using it unless it fails. I’ll see if I can find that info after work. Quote Link to comment Share on other sites More sharing options...
cwilbar Posted June 4, 2020 Share Posted June 4, 2020 IIRC correctly, the 158 and 258 are interchangeable. Atari no doubt used whatever was cheapest that month when purchasing chips. 1 Quote Link to comment Share on other sites More sharing options...
bfollowell Posted November 1, 2020 Author Share Posted November 1, 2020 (edited) It's time to revive my old thread. It's finally cooled off here enough, and I don't have so many outdoor chores to keep me busy, so I'm going back out to my garage workshop to start troubleshooting my 800XL again. One update. Don't ask me how in the world that I've possibly missed it up to this point, especially since I've read all the threads related to the crazy, 8-bit killing ingot power supply, but mine has a crazy, 8-bit killing ingot power supply! Part number 61982. So, the first thing I'm going to do before I start troubleshooting again is to buy a new PSU and cut the DIN off my ingot and make a new, modern PSU. I see most posts saying to get at least a 1.5A PSU. I bought this one for my last Raspberry Pi build. Would 2.5A be too much? https://www.amazon.com/gp/product/B00MARDJZ4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 Also, when I check my PSU, I get nothing but good voltages out of my PSU, so I don't think it blew up and destroyed my 800XL. I'm just being cautious before moving further. I get nothing but good voltages out of it when I check it so, unless it sort of went bad once, then back to normal, and isn't completely blown yet, I don't think it was my cause. Would someone please refresh my old memory? What is the typical result when the ingot blows? Does it pass crazy high voltages on through to the 8-bit? Does the current go sky high? What are the typical components/damage to the 8-bit when the ingot goes? Thanks. Edited November 1, 2020 by bfollowell Quote Link to comment Share on other sites More sharing options...
mimo Posted November 1, 2020 Share Posted November 1, 2020 2.5 amps is fine, your Atari will only draw the current it needs Quote Link to comment Share on other sites More sharing options...
bfollowell Posted November 1, 2020 Author Share Posted November 1, 2020 21 minutes ago, mimo said: 2.5 amps is fine, your Atari will only draw the current it needs That was kind of what I was thinking, but it's nice to have confirmation. Thanks! 1 Quote Link to comment Share on other sites More sharing options...
+Peter Rabitt Posted July 5, 2021 Share Posted July 5, 2021 Wow almost 6 month or so... Did you fix the 800xl and what was the problem... The reason I ask is I have one(800xl) with the same problem and the same chip replacements. I read your thread and have done almost everything the same except I do not have the Sys-ck yet... Peter Quote Link to comment Share on other sites More sharing options...
bfollowell Posted July 6, 2021 Author Share Posted July 6, 2021 (edited) 13 hours ago, Peter Rabitt said: Wow almost 6 month or so... Did you fix the 800xl and what was the problem... The reason I ask is I have one(800xl) with the same problem and the same chip replacements. I read your thread and have done almost everything the same except I do not have the Sys-ck yet... Peter No Peter, sorry, no luck yet. My work shop is in the garage and it's just too hot to work out there once the summer heat hits. I've been spending much more time with our youngest grandson too, and it hasn't left much time for troubleshooting. It's still sitting on my workbench though, alongside a working 800XL that I bought to restore and to help with my troubleshooting efforts. Hopefully, I'll get back to it in the fall. Since SysCheck doesn't work with it at all, I suspect I have something much more basic at play, such as a blown trace or bad component such as a bad resistor or cap. I'm probably going to have to start going through, component by component, and comparing readings to my good 800XL. Edited July 6, 2021 by bfollowell Quote Link to comment Share on other sites More sharing options...
+Peter Rabitt Posted July 6, 2021 Share Posted July 6, 2021 (edited) OK I can see the problem, heat, I am glad I have My computer room and kinda workshop in the spare small bed room. Yea the temps here are in the 100's almost every day... As to the second 800xl you got, I to have gotten a other 800xl, but be leave it or not it has the same problem,Green screen with vertical "black" bars.The 1st brother HAHAHA. As I opened the 2nd on I found it Has never been opened. So it was a shame to open it but I want a working 800XL... Hope the weather cools off for you soon, does not look good here until around Sept/Oct. time frame...Still working on My 800xl's looking for something... Ordered new parts just in case the ones I have here are also bad...If I find anything I will post it so maybe I can help you also... Stay COOL!!!! Peter Edited July 6, 2021 by Peter Rabitt Quote Link to comment Share on other sites More sharing options...
+Peter Rabitt Posted July 6, 2021 Share Posted July 6, 2021 bfollowell, I just found that the Delay line chip(in the new one I just opened) does not have all its outputs, and the other 800xl delay did not help when swapped. So maybe (on order today) when I get new ones it will all work... End of the week they said...for the parts... Peter Quote Link to comment Share on other sites More sharing options...
+Peter Rabitt Posted July 7, 2021 Share Posted July 7, 2021 Hi ALL,Just found the (maybe) problem with the two 800xl I have...As I stated in the above mesg. the delay line has missing outputs.... Per the above sch. I found Pin 1 was the input..Good signal. Then going to the next output Pin 4 and was as good as Pin 1.. Pin 6 was High (about4.8v) Pin 8 was High Pin 10 was High Pin 12 was working.. Note on the other delay in the other 800xl all sig where the same except 4 It was not working correctly.. Just though I would post this as I have search the AA looking for some help. As stated above I have switch out most of the real IC and was down to thro'ing this computer in the trash. Maybe I found the answer... Somewhere, when reading, I saw someone say something that he got a black screen and it was the delay line..So reading a lot of stuff here maybe the answer was their all the time.. Will find out this week end when the new parts get here from Best Electronics.. Peter Quote Link to comment Share on other sites More sharing options...
bfollowell Posted July 8, 2021 Author Share Posted July 8, 2021 (edited) I'm fairly certain that I've swapped the delay line chips between my non-working and working 800XLs and seen no change in either, so that tells me my delay line chip is good. I should also mention that, at some point in my troubleshooting, my XL went from the green screen shown in the first posts, to a solid black screen. I haven't checked it in a while, but I'm fairly certain the monitor is receiving a signal, it's just a solid black screen, not a dead video output. I have to admit, I haven't heard of a lot of defective delay line chips, so it seems awfully coincidental that you'd wind up with two 800XLs, both with defective delay line chips, but I guess stranger things have happened. Hopefully, the delay line swap will work for you, but it didn't help me. Edited July 8, 2021 by bfollowell Quote Link to comment Share on other sites More sharing options...
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