97.4PL not supported by Kenwood TS-811/TS-711?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by AD8BU, Oct 10, 2019.

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  1. AD8BU

    AD8BU Ham Member QRZ Page

  2. KD8TUT

    KD8TUT Platinum Subscriber Platinum Subscriber QRZ Page

    AD8BU likes this.
  3. AD8BU

    AD8BU Ham Member QRZ Page

    I took a closer look, and the ROM is burned right in to the main CPU. Its an NEC μPD7802G series micro controller. I'm not sure if its feasible to work with that or not.

    https://www.radiomuseum.org/tubes/tube_pd7802g.html

    Closest data sheet I could find: https://pdf1.alldatasheet.com/datasheet-pdf/view/127320/NEC/D780232.html

    The IO chip appears to be standardized, though:

    https://pdf1.alldatasheet.com/datasheet-pdf/view/66105/INTEL/D8255A-5.html
     
  4. K8JD

    K8JD Ham Member QRZ Page

    Before I retired I knew all the tones commonly used by the two way radio industry. Knew most of the Digital tone squelch codes too.
    Now I have been retired about 7 years I did not recognize the 97.4 as being a standard tone !!! :eek:
     
  5. AD8BU

    AD8BU Ham Member QRZ Page

    Wikipedia has a note about this specific tone that hints at it being added later, as a gap-filler due to it not being harmonically related to the other tones.



    After I got home from work, I cracked open my TS-811A to see what variant of the MX315 it had in it, and wouldn't ya know it, its got a Piexx board, not an original Kenwood. Cracked open my TS-711A and found another Piexx board. I'm sure batting a thousand with this project! :mad:

    I went ahead and tried the mod on the Piexx board just for kicks and its a no-go with it. Both of my boards have the numbers on the chip sanded off, so I can't get the specific datasheet to try to adapt the mod to it. I guess that repeater will be RX only on my rig, unless I can find an original TU-5 board to try the mod on it. Only other thing would be if MiARC lets the club change the PL, and the club is willing to do so.

    Bummer. :(

    At least I didn't fry anything when I attempted the mod.
     
  6. K7JEM

    K7JEM Ham Member QRZ Page

    Do you have some details about the chip? Like which pins have voltage and ground attached to them, how many pins total, where the inputs from the Kenwood go, etc. Maybe we can figure out if it's an off the shelf chip, or some special thing made for only them.
     
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    You may be able to use a UV flash light to read the number. Looks like it has a binary input. Is it 20 pins ? What is the crystal frequency ?

    There are boards for about $25 that will work.

    If you only want to add 1 tone, You can use a LM567. Even a 555 will work with a shaping network to make the square a sin wave.

    Are you using a frequency counter to look at the frequency ?

    Have Fun.
     
    Last edited: Oct 11, 2019
  8. AD8BU

    AD8BU Ham Member QRZ Page

    I will see if I get a chance to go all Big Clive on it and reverse engineer the schematic sometime this weekend. There's a lot more passives on the Piexx board than the original Kenwood boards.

    The main IC is a 20-pin surface mount chip. There is a smaller TI surface mount chip on the bottom.

    [​IMG] [​IMG]
     
  9. K7JEM

    K7JEM Ham Member QRZ Page

    The 2341I is an op-amp, maybe used to amp the output level:

    https://www.ti.com/lit/ds/symlink/tlv2341.pdf
     
  10. AD8BU

    AD8BU Ham Member QRZ Page

    I was finally able to make some time to trace out the Piexx tone board, or, at least the pins to the mystery IC. There are a few that I wasn't able to determine and may be NC.

    IC:
    1 - GND
    2 - ?
    3 - ?
    4 - Xtal
    5 - Xtal
    6 - NC
    7 - R6
    8 - R5
    9 - R2
    10 - GND
    11 - ?
    12 - ?
    13 - J1-8
    14 - J1-6
    15 - J1-5
    16 - J1-4
    17 - J1-3
    18 - J1-2
    19 - J1-1
    20 - J1-7

    J1:
    1 - IC-19
    2 - IC-18
    3 - IC-17
    4 - IC-16
    5 - IC-15
    6 - IC-14
    7 - IC-20
    8 - IC-13
    9 - Through some resistors and capacitors to Pin 6 pf the Op Amp
    10 - GND
     
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