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mozartpc27

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Everything posted by mozartpc27

  1. Attended this show today. A good time, with many exhibits different from last year. Was surprised to see very little Atari stuff - saw one 800XL and one ST (which was cool, I think the only other time I've seen an ST in action is at last year's show). No Coleco ADAM stuff. Lots of Commodore, lots of Apple (including an Apple I in a hand-crafted, original WOODEN case - not nailed to wooden boards, an actual wooden case!), one of the coolest exhibit was of 80s French computers (France was not an easy market to enter for non-French companies in the 1980s; as a result, there are lots of French-only computers). Had a lot of fun. Left thinking I should become an exhibitor. I have a pretty wide-ranging and eclectic variety of stuff - Coleco ADAM, Commodore 128 (which I have pretty well tricked out - has a wifi modem), a Commodore 64C, Commodore Plus/4 WITH 1551, Tandy Color Computer 2 (didn't see any of that line at the show), a TI-99 4/A (didn't see any TI-99 stuff being exhibited either, though there was a complete TI-99 set for sale with a Peripheral expansion box that I wanted, too rich for my blood however), and I have an Atari 800XL coming in the mail on Monday. Anyway, it's a great show that is also at a very worthwhile venue - the InfoAge Science Center has a great vintage computer museum and a great museum dedicated to old radio and television and other electronic equipment. Great stuff.
  2. I'll be there today with my wife and son. If anyone is around, say hello!
  3. Well, I replaced the RAM. And still - nothing. Is there any source out there for replacement Atari chips?
  4. Checked temps of all chips when the computer is operating - none overheating.
  5. Not sure what chip or chips are failing at this point. Took a stab at it with the Star Raiders cartridge. sloppy, just to be clear, the way I understand this is if you plug in a Star Raiders cartridge and the cartridge is able to work on start up, this would eliminate the CPU, ANTIC, and GTIA chips as the cause of the problem. Of course, nothing happened when I fired up the computer with the cartridge inserted. Your response confused me a little, because it seemed to be saying that getting a black screen on start up with the Star Raiders cartridge plugged in indicates that the CPU, ANTIC, and GTIA chips are good, not bad. So what I am asking is: which is it? Does a black screen on start up with the Star Raiders cartridge inserted indicate that that the CPU, ANTIC, and GTIA chips are likely good, or likely bad? Sorry for my confusion.
  6. I have an Atari 800XL I picked up that is non-working currently. I've been through testing of the PSUs that came with it (there were two), at least one is outputting just a shade over 5V, then I tested all chips on the board, also all receiving 5V. So I found this thread and did this - picked up a copy of Star Raiders. Plugged it in, the computer still not working. My question: does this then ISOLATE the problem with the computer to the CPU, Antic, or GTIA chips, or could it be anything on the board?
  7. A big part of me would like to go to this, but fmaily commitments make it unlikely, sad to say.
  8. Yeah, that may be where I have to go with this eventually. Of course, the point was to acquire 1 working system. So buying one to test another... I should just toss the non-working one haha.
  9. I do not have the capability to test the EPROM myself. Feel like this is the likely culprit, but that is admittedly more of a guess than anything scientific.
  10. Cool, thanks. I have a Commodore monitor with a chroma / composite hook up. Can't get the Atari to output to that either - I assume this eliminates an issue strictly with the RF output itself (and perhaps with the CTIA chip?). Based on another thread, I ordered a copy of Star Raiders - apparently this cart has a diagnostic component to it and, if it boots, will eliminate certain chips as the cause (CPU/ANTIC/GTIA). See this thread - http://atariage.com/forums/topic/177258-atari-800xl-nothing-on-screen/ Otherwise, looks like I might need a "parts" 800XL. Not sure when I will be able to pick one up for that.
  11. OK, I have now also correctly identified the ground and +5 pinouts on the four chips along the bottom (and their functions), and, using the correct pins to measure, they all measure out at 5V. And yet, no display, no sound. So what next?
  12. Well, on the one hand, the 28 pin OS ROM is the one that appears to be a "custom" replacement. It is the "Omniview" XL/XE by David Young, and looking at the chip more closely, it has the following information on it: N JAPAN 8505 00009SS0 HN4827128G-25. On the other hand, the ROM chip is among the chips I measured receiving 5V. I guess I still need to re-measure after looking at the schematic, but still. A refresher of what I have looked at in terms of the three chips above the right most chip along the bottom row (the picture is on the previous page):
  13. Don't have a closeup for you right now, but I did locate the sticker which I believe was on the chip that fell off. it says: A stylized logo that appears to make the letters cdy (it's the "c" at the beginning I am not 100% on - it's definitely a "d" and a "y") "Omniview" XL/XE by David Young And I just realized that... duh... "dy" must stand for "David Young." Not sure if the thing around the dy is supposed to be a "c" or not. From another thread on the board, looks like that was a replacement OS: Is this the likely culprit? How would I go about getting a replacement for this chip... not necessarily another of these custom chips, but whatever chip was originally supposed to be there?
  14. This is the chip that had a sticker on it with the manufacturing information. The sticker became detached long ago - it fell out when I opened up the computer. At that time I didn't realize what it was and I've misplaced it... so I can't tell you much about it. Which one is the OS ROM and which the BASIC?
  15. Nothing discernible. Slightly longer hang on a full orange screen (probably less than a full second, but plainly visible), then to black.
  16. OK, so here we go: I understand the bank of 8 smaller chips all the way on the left of the picture to be RAM - they all read at or near 5V (I am using an analog multimeter)with my other PSU, which reads at 5V at the DIN when it is not plugged into the computer. Additionally, all of the "smaller" chips - so the three that are nearest the bank of RAM on the left, the 7 grouped in the middle, and the two little guys to the right with the green wire running over them, will produce a reading of 5V with some orientation of the test leads (I am not always sure what is the ground and what the "positive" pin to use on these, but ultimately I was able to read 5V coming from all of them). The question I have is now about the four across the bottom, and the three running lengthwise above them on the right. I have included all the information from the labels of the chips in this list. They are listed across from left to right (the first 4), then in ascending order up from above the last in the line of horizontally oriented chips at the bottom (the last three): Bottom Across, left to right: OKI Japan © 1979 Atari, M3983 C014805-22: Ground test lead positioned bottom right, positive test lead positioned top left: 4V IMP 8324 LGA C021697-31 © 1983 Atari: Ground test lead positioned bottom left, positive test lead positioned top right: 5V (if I do this one with the ground test lead positioned bottom right and positive test lead positioned top left, it reads around 1.5V) 8311 C-014806-03? (last digit(s) too faded to read): Ground test lead positioned bottom right, positive test lead positioned top left: 4V C014795-12 R6520-26 8324: Ground test lead positioned bottom left, positive test lead positioned top right: 4V Moving upward one at a time from the last chip in that bottom row (C014795-12): AMI 8328BLE C0122948-01 C03051 Korea: Ground test lead positioned bottom left, positive test lead positioned top right: 5V Label fell off, lost it (it was inside the computer when I opened it up, saw it, don't know where it got to): Ground test lead positioned bottom right, positive test lead positioned top left: 5V NCR2364-30 F807612 N8326 C060302A-29 © 1979 Atari: Ground test lead positioned bottom right, positive test lead positioned top left: 5V
  17. I should have tested and posted this yesterday, but I have a second PSU that, when used to fire up the 800XL, produces only a *black* screen. There might be a flicker of orange for a second, but then black. The voltage out on this PSU is right around 5V, and that's what I get at all of the 8 RAM chips. However, at the longer chips across the "bottom" (if I am looking at the computer in its normal, ready-for-use position, but opened up), I get readings of 4V or less in some cases. I don't know what all the chips are so I haven't been able to find pinouts so I am testing correctly. I guess I should post a picture. I'll work on that. One is copyright 1979 Atari, another 1983.
  18. Yeah, it is an ingot. OK, I can replace it. What other of my components will be fried? RAM, presumably, from what I've read.
  19. Every chip I've measured seems to be getting between 4-4.5 volts. When I just test the PSU, its outputting closer to 6. The red light comes on. I have yet to hear anything coming from the system. I've tried hooking it up to my tube TV via both RF and Composite, and to a Commodore monitor I have through composite. Nothing. I just sat with the computer on for a few minutes - nothing seemed to be overheating. I have re-socketed some, but not all, of the chips. 5 of the 8 RAM chips are sort of a bitch to get out - I don't want to damage them trying to re-socket them!
  20. Thanks... I need to get back to working on this, but haven't had a lot of spare time lately. The computer is sitting here and pulled apart.
  21. I see. In either circumstance, the multimeter appears to tell me the power supplies are good... so my question is what should I try next in terms of trouble shooting, or is it even worth it?
  22. I mean calibrating the multimeter. I watched an internet video about how to use an analog meter, here: He explains how to make sure the meter reads zero resistance (i.e., needle is over 0) when there is in fact zero resistance.
  23. Aha. Well in that case, one of the two power supplies seems to be outputting slightly more than the promised 5V (the one that gives visual feedback on the screen), and the other is right at the number (could be a calibration issue - when I "zero out" the unit the needle moves ALL the way to the right - off the printed scale). so it would seem at least one of these PSU is outputting the correct voltage. What ought I to try next? The RAM?
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