Image Map Image Map
Page 3 of 11 FirstFirst 1234567 ... LastLast
Results 21 to 30 of 104

Thread: Osi c4p

  1. #21
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,811
    Blog Entries
    3

    Default

    For an experiment, I pulled out the 8T26 at U3H, and I bent out pins 12 and 14. Then I plugged back in and fired up. Now there is signal on pin 14. Nothing at all on pin 12 (neither high nor low, which makes sense since it is tied to and thus driven by pin 14?). I'm just reading up on the 8T26 but it seems like the problem must be towards that 175 somewhere.

  2. #22
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,811
    Blog Entries
    3

    Default

    Got it!!

    So basically I followed the trace from U4G pin 13. It's hard to explain, but essentially if you think of three vias arranged as points of a triangle, the trace coming from pin 13 attaches to the bottom left point, and then the trace runs under on the other side to the bottom right point, coming back up and running a short distance under U4H before going under again through another via, and a straight shot to pin 3 of J4I (the keyboard connector).

    On close inspection, I realized the metal cap that runs over all three 'points' of the triangle was really close, maybe even touching. I also found what appeared to be corrosion or maybe old solder flux (the previous owner didn't do a great cleaning job on that). Anyway, it appeared to have 'metastasized' to the point that it may have been making contact with either the metal body of the cap, or the top point of the triangle (which is not supposed to be connected to the other two points), or both. Anyway, I moved the cap as much as I could upwards, scraped away the residue, and immediately I had everything working properly!

    Dave you were invaluable as always. I think I was mostly on the trail... I just wasn't confident that KD2 necessarily had to be having some kind of activity on it.

    Anyway, now I'm going to try, without breaking anything else, to put it all back together and play with it a bit. I'm curious to see an OSI with colour!

    And then I can pack this away for a bit while I await the tapes, and try to get this adapter for the Microkit finished so we can see what the rest of the 1702 data is.

  3. #23
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,811
    Blog Entries
    3

    Default

    One thing I *am* curious about - I was really hoping to use my other, empty C4P case to plug my plain jane 500 and 440 boards into.. however I discovered that the -9V line is not connected to anything. I had wrongly assumed OSIs were always rigged up with +5, +12 and -9V. I guess not. I'm not sure how I'll deal with that, or if I will, but in the meantime I was looking the backplane of the 'full' C4P I've been working on, and I did find this large resistor attached to the -9V line. I'm not sure what that is supposed to do.. looks like it goes to pin 25 of one of the DB25 ports. Looks like there is another wire attached there too that was cut. I'm wondering if he was feeing in something slightly higher than -9V and the resistor cuts it down? Or maybe just using the -9V rail/pin for something else entirely.

    20191229_122446.jpg

  4. #24
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,811
    Blog Entries
    3

    Default

    Okay, one more potential problem.

    So far everything operates just fine, however I decided to try out the color mode. You invoke color mode by using a POKE statement, in this case, POKE 56832,5 (64 columns, no sound). However, when I do that, I get this:

    20191229_205710.jpg

    Doesn't photograph very well, but you get the idea. It throws up color blocks all over. I'm assuming this is a bug, not a feature. I'm pretty sure the color video RAM is good.. it was among the RAM I tested in the Hazeltine. Not really sure on this one. First time I've ever seen any kind of color out of an OSI product.

  5. Default

    Try writing a program to preset all the colour ram to a certain value. If it works, then the ram is ok.

    I had a computer where the colour was an extra part, and you had to initialise the ram yourself.

  6. #26
    Join Date
    Jun 2014
    Location
    Sydney, Australia
    Posts
    13

    Default

    Hi Falter, Robbbert, et al.

    Try this and let us know what you get:

    #SHOW ALL CHARACTERS
    10 FOR T = 0 TO 255
    20 POKE 57344+T,T
    30 NEXT
    40 FOR T = 0 TO 255
    50 poke 53248+T,T
    60 NEXT
    RUN

    # TURN COLOUR ON
    POKE 56832,4

    Should look something like:
    C4Pa.jpg

    Cheers,
    Red

  7. #27
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    3,448

    Default

    Good work that man!

    Conductive flux/corrosion etc. once again. Always a good place to start with a bright light, magnifying glass and some flux cleaner.

    I agree with the previous post. The colour information will require additional RAM. Either that RAM could be faulty or, as explained, it may contain garbage. If it is not initialised prior to entering colour mode, you may get random foreground and background colours. With a lot of [SPACE] characters on the screen by default, you will get random blocks of background colours (exactly what you see)...

    Dave

  8. #28
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,811
    Blog Entries
    3

    Default

    Quote Originally Posted by RedskullDC View Post
    Hi Falter, Robbbert, et al.

    Try this and let us know what you get:

    #SHOW ALL CHARACTERS
    10 FOR T = 0 TO 255
    20 POKE 57344+T,T
    30 NEXT
    40 FOR T = 0 TO 255
    50 poke 53248+T,T
    60 NEXT
    RUN

    # TURN COLOUR ON
    POKE 56832,4

    Should look something like:
    C4Pa.jpg

    Cheers,
    Red
    Hmm.. nope.. I get this:

    20191230_101008.jpg

    I can see it drawing out all the characters when I run the program, although they disappear above the visible range of the screen. But as soon as I run the color invocation, it does as you see there.

  9. #29
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,811
    Blog Entries
    3

    Default

    Tried changing the color RAM as well as the 8T26 that handles them... no change.

  10. #30
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    3,448

    Default

    So there is something not right here somewhere...

    Graphic mode is described here on page 27 http://www.osiweb.org/manuals/c4man.pdf.

    Character memory starts at 53248 whilst colour memory starts at 57344.

    Poke 56832,4 should set 32 column mode, no sound and enable colour. I see your screen is in 32 column mode, but Red’s screen appears to be in 64 column mode still.

    When your machine starts up, is it in 32 or 64 column mode and how many lines of text are there by default? Just type random garbage to find out! I see very early on that it was in 64 column mode.

    Let’s make sure the machine works in monochrome mode first. Do you get all of the correct characters displayed?

    I suspect either colour RAM is not being written to or read from. I have a simple way of checking this later.

    By the way, what type of ROMs have you got in this machine, and have you played with the machine code monitor yet?

    And welcome to the forum Red! Your posts will be moderated for a few more posts.

    Dave

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •