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  1. Thread: Wtb: Sgi o2

    by dhoelzer
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    4
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    234

    Sorry, I haven;t forgotten you, I'm just out of...

    Sorry, I haven;t forgotten you, I'm just out of town until October 2. :(
  2. It appears to read as 470 ohms, which is correct.

    It appears to read as 470 ohms, which is correct.
  3. That's what comes of 30 years marinating in mouse...

    That's what comes of 30 years marinating in mouse urine. It's clearly not good for electronics. :)

    That said, it appears that the waveform matches pin 3 on UC3, but has a difference in magnitude....
  4. Nope, I've looked at that super carefully. The...

    Nope, I've looked at that super carefully. The 555 side of the inverter looks perfect. I'll break out the USB microscope soon to look over the traces.
  5. Ok. I have a "Leak Tester" that I've never had...

    Ok. I have a "Leak Tester" that I've never had success with. Maybe this is the job for it. I'll take a close look later today after I'm all packed up.

    Did you mean that to be "UD15"? This is a...
  6. That looked ok. +5 on one side, 200khz signal on...

    That looked ok. +5 on one side, 200khz signal on the other. :)
  7. Ok, it's definitely not coming from the ~RES pin...

    Ok, it's definitely not coming from the ~RES pin on the processor, but it is still only present when the processor is inserted. I put a CPU into a socket and bent pin 40 out to the side. Tying that...
  8. Ok... Well.. One last question before I check...

    Ok... Well.. One last question before I check out. I started dabbling this morning and found two things...

    First, leg 13 on the 7407 hex buffer seemed to have separated from the body of the chip,...
  9. Just a note that this thread will be on hiatus...

    Just a note that this thread will be on hiatus until October (unfortunately). I have three weeks of work across the US, so I'll be traveling and out of my lab. I plan to resume my exploration of...
  10. Thanks! Will-do. I'll go read up on them.

    Thanks! Will-do. I'll go read up on them.
  11. My 2114 testing rig has proven very useful and...

    My 2114 testing rig has proven very useful and definitely shows that I have a bunch of marginal chips.

    Tests performed:

    Iterative Write/Read Testing:
    Iteratively writing incremental nibbles...
  12. Sigh. That might have been a wild goose chase. ...

    Sigh. That might have been a wild goose chase. I think it was the Arduino failing to properly drive the pins. Well, two more chips socketed. I think I'm at least halfway through the logic chips...
  13. Strike that... I'm actually seeing that pins 13...

    Strike that... I'm actually seeing that pins 13 and 14 in socket UF7 seem to have something fighting to drive them. When the Arduino tries to pull them to ground they actually float at 1.4...
  14. In other news..

    As a result of the below, I've managed to determine that the video circuitry is all just fine, though I did have a couple of bad 2114s. This narrows things down in two ways: It appears that the...
  15. I don't hate them... I'm just scratching my head...

    I don't hate them... I'm just scratching my head to figure out what the heck is going on. First it looks like a problem in the DRAM, then I get crazy video artifacts, then it sort of works, then the...
  16. Yes, I do get a checkerboard. :) That's one of...

    Yes, I do get a checkerboard. :) That's one of the first things I confirmed when I started working on this beast.

    I have another very interesting idea I'm going to explore in the AM.. I'll post...
  17. Progress and squirrel-chasing

    I have become slight distracted from my DRAM/ROM testing project by the SRAM video troubles. Yes, I know I'm easily distracted... It's because the video RAM problem seems infinitely simpler by...
  18. After much progress, I'm again in a lull. The...

    After much progress, I'm again in a lull. The PET diag ran for hours, but screen artifacts began to develop, especially after me inadvertently inserting that KERNAL ROM incorrectly! I've now been...
  19. To answer my own question, I've just probed pin...

    To answer my own question, I've just probed pin 20 on every eprom socket... While PETDIAG is running, only 0xF000 is active, so that's good news.

    In the meantime, I think I just killed my original...
  20. (As you read this, have this question in mind:...

    (As you read this, have this question in mind: "Even as I type this, though, I'm forced to wonder if the actual problem might be a failing 4 to 16 decoder that is incorrectly turning on the chip...
  21. Just an update. I spent a great deal of time...

    Just an update. I spent a great deal of time thinking, studying the schematics, and reading. One or two of you folks have pointed toward something being active on the bus, and my suspicions are...
  22. I have verified good contact across the address...

    I have verified good contact across the address and data lines all the way down to UD3, but I'll try it out again to be sure. I'm checking from the shoulder of an eprom down to the UD3 socket.
  23. Thanks Frank. Yes, 4116 and 8116 are equivalent....

    Thanks Frank. Yes, 4116 and 8116 are equivalent. Was just clarifying, sorry if it sounded otherwise. :)

    I'm pausing to regroup until tomorrow afternoon when the other power supply arrives. It...
  24. This is all 8116 DRAM. Teeth marks are...

    This is all 8116 DRAM.

    Teeth marks are definitely a possibility. Remember, this PET was a mouse clan's home in some guy's garage for a couple of decades. I've finally gotten the last of the...
  25. Thanks Dave; the thing is that the system isn't...

    Thanks Dave; the thing is that the system isn't even starting well enough now to run your tests! (which it was two days ago)

    I replaced all of the .1 uF caps on the DRAM last night. I'll pull out...
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