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Aquired an SDK-85

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  • orion3311
    So I scored an Intel sdk-85 in non-working order. It seems to mostly boot to the 80 85 prompt but it randomly will bolt to garbage. I tried swapping the cpu
    Message 1 of 9 , May 11, 2014
      So I scored an Intel sdk-85 in non-working order. It seems to mostly boot to the 80 85 prompt but it randomly will bolt to garbage. I tried swapping the cpu and the ls138 above the cpu but neither helped.Unfortunately I dont have an 8085 pod for my Fluke, however theres only a few other parts on here. Short of ebay does anyone have an Intel 8155 (ram) or 8355 (rom)(blank)?I kinda doubt the keyboard controller is bad but I guess it cant hurt to ask for an 8279 as well?Willing to buy/trade, let me know. Thanks!
    • Dave McGuire
      ... The 8355 is a mask ROM; you won t find blank ones. If memory serves, the 8755 will plug in. I have several of those and can send you one if needed; ping
      Message 2 of 9 , May 11, 2014
        On 05/11/2014 11:00 PM, jeffg@... [midatlanticretro] wrote:
        > So I scored an Intel sdk-85 in non-working order. It seems to mostly
        > boot to the 80 85 prompt but it randomly will bolt to garbage. I tried
        > swapping the cpu and the ls138 above the cpu but neither helped.
        > Unfortunately I dont have an 8085 pod for my Fluke, however theres only
        > a few other parts on here. Short of ebay does anyone have an Intel 8155
        > (ram) or 8355 (rom)(blank)? I kinda doubt the keyboard controller is bad
        > but I guess it cant hurt to ask for an 8279 as well? Willing to
        > buy/trade, let me know. Thanks!

        The 8355 is a mask ROM; you won't find blank ones. If memory serves,
        the 8755 will plug in. I have several of those and can send you one if
        needed; ping me off-list with your address if so. Send me a hex file if
        you want me to program it with something first.

        8279s are pretty tough to find.

        Instead of shotgunning it, why not troubleshoot? The SDK-85 is a
        pretty simple design, and everything is easily accessible.

        First off, how's the power? Next, how does the clock look?

        -Dave

        --
        Dave McGuire, AK4HZ
        New Kensington, PA
      • orion3311
        Yeah Im hoping to do a little troubleshooting before shotgunning but I figured if the parts are around maybe I should just keep a stash of spares in the box.
        Message 3 of 9 , May 11, 2014
          Yeah Im hoping to do a little troubleshooting before shotgunning but I figured if the parts are around maybe I should just keep a stash of spares in the box. Im far from green in troubleshooting but the heavily integrated parts are throwing me off...Im used to seperate ram/rom/io.That said, power is good and clock seems good. Reset key does reset it but again it either boots to 8085 with no dash (and no keyboard responsr) or just random garbage.Now that Im playing with it a little it almost seems like the second half of the display is static...may be a clue.
        • joshbensadon
          Hi Jeff, I have an MCS-85 System Design Kit.... I think it s the same thing, (SDK=System Design Kit?) I haven t powered mine up yet, nor is it going on the
          Message 4 of 9 , May 11, 2014
            Hi Jeff,

            I have an MCS-85 System Design Kit.... I think it's the same thing, (SDK=System Design Kit?)

            I haven't powered mine up yet, nor is it going on the bench anytime soon, but a quick look shows it's using Augat Sockets.  Those sockets were known to be flakey back then...  add 35 years and I'm sure the problem is bad sockets.  I remember in the late 80's, we had a bad batch of Augat sockets, when the chips warmed up, the contacts would drop out.

            Otherwise, 6 chips on the board, what can go wrong?

            Regards,
            Josh Bensadon
          • Systems Glitch
            ... I have a SDK-85 as well, picked mine up in unknown condition. It exhibited symptoms similar to yours. Here s my writeup on fixing it:
            Message 5 of 9 , May 12, 2014
              > So I scored an Intel sdk-85 in non-working order. It seems to mostly boot to the 80 85 prompt but it randomly will bolt to garbage. I tried swapping the cpu and the ls138 above the cpu but neither helped.

              I have a SDK-85 as well, picked mine up in "unknown" condition. It exhibited symptoms similar to yours. Here's my writeup on fixing it:

              http://glitchwrks.com/2013/01/02/Intel-SDK-85/

              Not-soldered-in socket, a broken trace, and a pile of cold/missed solder joints.

              Thanks,
              Jonathan
            • orion3311
              Jonathan - I was the guy asking you a million questions about yours at VCF...and you re the reason I got this one. :-) While I haven t taken it out to the
              Message 6 of 9 , May 12, 2014
                Jonathan - I was the guy asking you a million questions about yours at VCF...and you're the reason I got this one. :-)

                While I haven't taken it out to the garage and really gave it a solid once over yet, physical inspection by dining room light looks ok. Some soldering that should be fixed up but nothing that looks game changing. The sockets are machine pin sockets, and while I don't like those either, they should be ok. Everything's pretty clean.

                Poking around with the oscope last night I can definitely see that there's still activity on the busses, the enable lines for the rom/ram seem to have activity so its doing something. Only thing I noticed was that the IRQ line on the keyboard controller (8279) went from low to high after pressing the first key, which is I believe what it's supposed to do, but I also saw that I think A0 never went high so technically its held in write mode the entire time.

                I'm really limited on time the next two weeks so I may have to shelf it until the workshop. I bought this as a learning experience so maybe I'll have to cobble up a temp rom replacement (or use my virtual rom I have somewhere) to do a ram test or something.

                Btw I have access to all the good troubleshooting toys including logic analyzer, 100mhz oscope, etc etc.

                Thanks all for your help so far!

                -- Jeff aka Bags
              • Systems Glitch
                ... Glad I could help! ... Bad RAM is a possibility -- it should be entirely within the first 8155, so you can swap that out as a quick test. From what I ve
                Message 7 of 9 , May 12, 2014
                  > Jonathan - I was the guy asking you a million questions about yours at VCF...and you're the reason I got this one. :-)

                  Glad I could help!

                  > I'm really limited on time the next two weeks so I may have to shelf it until the workshop. I bought this as a learning experience so maybe I'll have to cobble up a temp rom replacement (or use my virtual rom I have somewhere) to do a ram test or something.

                  Bad RAM is a possibility -- it should be entirely within the first 8155, so you can swap that out as a quick test. From what I've read about others' experience with bad 8355 devices, they typically are either OK or dead. With it sometimes displaying the monitor prompt, I'd bet it's something intermittent.

                  If you don't have it sorted out by the workshop, assuming I'm able to make it down, I can bring my SDK-85 and we can work through it.

                  Thanks,
                  Jonathan
                • orion3311
                  Thanks to everyone for offering to help, but after replacing the 8155 (ram), she lives!!
                  Message 8 of 9 , May 30, 2014
                    Thanks to everyone for offering to help, but after replacing the 8155 (ram), she lives!!
                  • Systems Glitch
                    ... Awesome! Thanks, Jonathan
                    Message 9 of 9 , May 30, 2014
                      > Thanks to everyone for offering to help, but after replacing the 8155 (ram), she lives!!

                      Awesome!

                      Thanks,
                      Jonathan
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