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RTC for 4D

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  • RTC for 4D

    Going through a Model 4D motherboard that appears to have suffered some damage through exposure to the elements I found a few "features" that at first I didn't recognize:

    First, there are a number of "jumper" or "bodge" wires running here and there. I'm no expert but even the early NGA boards didn't have this array of "extra" wiring. And at U4 there is a strange piggyback apparatus where the system ROM should be. Prying things apart (carefully, due to rust on the legs of the ICs and in the sockets) I found a small circuit board with a Dallas DS1216 inside the carrier.

    Apparently the DS1216 is still available from Maxim, but I'm wondering if anyone knows who made this modification and whether any of the extra wiring is in support of this modification.



    Mobo.jpg RTC.jpg

  • #2


    • #3

      I believe you're right, thanks. Not sure the chip can be replaced and battery is most likely dead, but interesting idea. Maybe dissect for reproduction...



      • #4
        Found this too:


        • #5
          Indeed. This is getting more interesting; thanks again for pointing this out.



          • #6
            The type of foam you have the chips stuck in generates static which isn't good for the chips. You should put some Aluminum foil on the foam before putting the chips in it.



            • #7
              Thanks for the tip. The foam was sold as anti-static; I'll have to verify that. But I never would have thought of tinfoil.



              • #8
                Anti-static, but not conductive, according to the supplier. Also the supplier, McMaster-Carr, notes that the anti-static properties diminish over time.

                Bottom line is that next time I'm in McMaster-Carr I'll pick up some of the conductive foam. Meanwhile I'll use tinfoil. Thanks for the heads-up.




                • #9

                  Can you confirm where the two wires route to?


                  • #10
                    I am in the process of mapping the DS1216 to its carrier; not all DS pins are carried out. The carrier is 28 pin and U4 is 24 pin so the carrier "hung over" U4 and the ROM, which sat on top, was aligned toward the bottom of the board, not filling all of the pins of the carrier. Accordingly some jumpering was added to accommodate for the smaller size of U4. See the pic below. Pin 28 Vcc tied to pin 26, VccB, and pin 20, Chip Enable (active low) tied to ground, it appears to me from the datasheet.

                    Meanwhile, I found this at Electronic Surplus:

                    Apparently still available through MAXIM.


                    Last edited by clh333; February 17, 2021, 04:02 PM.


                    • #11
                      I did upgrade to this board about 1989.

                      It is smartwatch upgrade published in Misosys quarterly.



                      • #12
                        Now that I looked at pic I cannot believe I did that soldering, maybe one of my employees.