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  1. #1

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    Kraft 2.4 ghz conversion help needed

    Trying to do a Frsky comversion on a 1980 5c and a 1979 7c.where to pick up the ppm signal from the encoder board as well as the +v and -v,alot are using the trainer port on other systems which the 7c has but the 5 c does not.Anyone have any suggestions .

  2. #2

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    RE: Kraft 2.4 ghz conversion help needed

    Check http://groups.yahoo.com/group/MP8K/ and ask that question.

  3. #3

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    RE: Kraft 2.4 ghz conversion help needed

    not a member

  4. #4
    Michaelj2k's Avatar
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    RE: Kraft 2.4 ghz conversion help needed

    He's crazy Lew, he builds toy airplanes!"
    Frank Towns - Flight of the Phoenix (1965)

  5. #5

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    RE: Kraft 2.4 ghz conversion help needed

    I have done conversions on 2 Kraft radios. Please look at the info here.
    http://www.rcuniverse.com/forum/m_10...m.htm#10097051

    I found that I had to modify the signal on the PPM line. The 2 radios I did the modulation went to almost the + battery voltage and the Frsky wants to see a modulation swing of 5 volts. Also I inverted the modulation signal before feeding into the Frsky module. This is simple to do and will only take a 5 volt regulator, an NPN transistor (2N2222) and a couple of resistors.

    I don't know for sure if you will have to do this. It worked for me. As far as finding the PPM modulation point, it is easy with a scope.

    I didn't tell you what you wanted but I hope this may help.

    Pete

  6. #6

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    RE: Kraft 2.4 ghz conversion help needed

    that is what I was looking for thanks

  7. #7

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    RE: Kraft 2.4 ghz conversion help needed

    modeltronics,
    if you leave the 72mhz Kraft rf module in place and just solder the frsky hack module to the encoder board or trainer port
    won't their be rf transmision on the 72 mhz band as well as the 2.4 ghz band? I have seen the frsky hack module used on
    jr 6102 and 7202 tx with the all in one board,rf board is part of the encoderboard.doesn;t the same thing happen where the 72 mhz rf section is still live as well as the
    2.4 ghz module ?haven't seen this asked before or brought up before.

  8. #8

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    RE: Kraft 2.4 ghz conversion help needed

    Removing the crystal will stop transmission on 72MHz

  9. #9

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    RE: Kraft 2.4 ghz conversion help needed

    aerowoof,

    For both the 7C & 5C, if you look at the wires at the RF module, the red wire is +9.6 V (switched batt +), the black wire is 0 V (ground) and the yellow wire is PPM (modulation, neg pulses at or near batt voltage). You can also find these wires at the encoder on a 4 wire plug along with an orange/blk wire. To convert PPM to 5V positive pulses, connect the yellow wire through a 47K resistor to the base of a 2N2222 or 2N3904 transistor. Connect collector through 4.7K resistor to 9.6V and emitter to ground. Connect a 5V or 5.1V zener diode (1N5231 or similar) directly across emitter and collector, cathode (stripe end) to the collector. PPM output for the FrSky module is at the collector. If you need more detailed info, PM or email me - smallrc@yahoo.com. To disable the 72 MHz RF, simply remove the module. Hope this helps...
    SmallRC, the Kraft Collector

  10. #10

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    RE: Kraft 2.4 ghz conversion help needed

    Sorry. Some how I timed out on RCU and it double posted for me

  11. #11

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    RE: Kraft 2.4 ghz conversion help needed

    Sorry to take so long to get back to you. I have been away from a computer for a few days. The way smallrc talks about should work very well. I did not have a zener diode so I used a regulated 5 volts on the collector of the NPN I used and inverted the signal at the same time. If I had to do it over again I think I could do it with a 741 op-amp to invert the PPM signal and limit it to 5 volts. On the Kraft Spectrum I pulled the module out. On the '74 Kraft it did not have a module and I just removed the crystal.

    Pete

  12. #12

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    RE: Kraft 2.4 ghz conversion help needed

    trying to find parts at radio shack they don't seem to carry the recommended number but did find this,would it work?
    NTE5010A 5.1V 0.5W Zener Diode

  13. #13

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    RE: Kraft 2.4 ghz conversion help needed

    found these schematics for the 5c and 7c an posting them in order to help others
    Attached Files Attached Files

  14. #14
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    RE: Kraft 2.4 ghz conversion help needed

    ORIGINAL: aerowoof

    found these schematics for the 5c and 7c an posting them in order to help others
    Where did you post them?

    Thanks,

    Got it, Thanks again.
    Dan Thompson http://sites.google.com/site/ckffinc
    MicroPro8000 http://sites.google.com/site/mp8kinfo

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    RE: Kraft 2.4 ghz conversion help needed

    post above yours kept getting an error message finally went thru.


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