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Yamaha DX7 2FD Battery problem ?

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  • Yamaha DX7 2FD Battery problem ?


    Someone gave me this keyboard with a floppy issue that wouldn't stop.
    On the motherboard I found a completely empty CR2032 battery.
    I replaced it by a new one but found that it drained quickly.
    I think there is a problem with the system reset.

    Any idea ?

    Thank you

    PST518 = PST518 B-2 (IG116200)
    Click image for larger version  Name:	Yamaha DX-7_SystemReset.jpg Views:	0 Size:	22.6 KB ID:	780484

  • #2
    Have you checked C42 for short?


    • #3
      Of course, I checked c42 tantalum capacitor = OK
      I also tested the transistors = OK
      Now I check the voltage.
      At rest (Pwr Off) VBat = 3V1 VR53 = 2V9 on both sides.
      Tomorrow I power up !


      • #4
        I took the measurements under power On.
        The 2 transistors are saturated so that the voltage on the capacitor rises nearly 5V, then the diode is blocked and the battery is isolated from the whole.
        Everything indicates that the reset circuit is in good health.

        I go back to the original problem : The diag program does not start. It stops at the first instruction.

        I think when the battery go down, the ram which should contain the tests become erased and the system freeze halted on the first line.
        To reload I need the ROM cartridge N ° 3 which of course has disappeared.
        Aïe Aïe Aïe !



        • Drawbar Dave
          Drawbar Dave commented
          Editing a comment
          Use DX manager. You can send these ROMs as Sysex files over midi if you have a midi interface and a computer.

      • #5
        Thank's DD I will try this and report.


        • #6
          Originally posted by Jyvoipabo View Post
          Thank's DD I will try this and report.
          All those ROMs are available on line as Syx files :-)
          B3, XB3, XB5, M102 Factory Split x2, TTR-100, L162
          145 x3, 251, 760 x2, Farfisa Compact Duo, Compact Deluxe, Lowrey Berkshire, Heritage


          • Sweet Pete
            Sweet Pete commented
            Editing a comment
            Thanks Dave! This 1984 Yamaha TX7 is living on borrowed time.Got a fresh 2032 battery in there no worries.
            Battery replacement time for many older devices these days.
            Still have the original cassette tape ROM's and sys-ex: too funny! And the adapter cable,user manuals etc.
            Way easier to use USB these days though.

        • #7
          WOW!! I did not expect to find this thread here! How perfect as I just did the removable battery mod on a IIFD That also has an E! Card installed and I will be bringing it all back up in the next few days.

          As an aside a while back I came across an older keyboard player that had a DX to which he had gaffer taped a few small fx boxes. It was well worn and obviously loved. This guy had managed to eel out the best Hammond emulation that I had ever heard at that time. My old broadcast theory says that ANY signal can be replicated with a suitable number of sine waves which seems to make fm a good candidate for Hammond emulation especially with the added E! Capabilities. Thanks!


          • #8

            CR2032 backup battery replaced.
            46 Tactile switch replaced including key 16 (Disk) which was blocked.
            Now, floppy drive = OK format and all the switch works.
            Tried to connect to a Win10 computer using a cheap midi-USB interface and 'MIDI connections' software : OK

            Syx Files : Does a (free and simple to use) windows software exist ?



            • #9
              Some observations:

              -The Yamaha DX7 and the DX7-II are quite different machines. The procedures of one do not necessarily apply to the other. But the cartridges are the same.
              -In Europe the cartridge that allows to restore the system is #1.
              -Before writing in the internal ram you have to set the write protection to OFF. It automatically returns to ON each time the power is turned on.
              -Chinese low cost USB-midi cables are easy to install. Really ?
              -.Syx files are easily found on the web.
              -'Bome Send Sx ' is a small, free windows software. Easy to use for sending .Syx to the DX7.

              Ultimately I will be unable to explain how I did it and I'm not really sure of the result, but I managed to restore this DX7-IIFD

              Last tip: If you need to replace the battery of a DX7, try to keep the RAM powered. This is normally not a problem as long as the battery is not completely dry and C42 not discharged.