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Kraft 2.4 ghz conversion help needed

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Old 01-23-2012, 02:53 PM
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aerowoof
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Default 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 .
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Old 01-23-2012, 05:23 PM
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Default RE: Kraft 2.4 ghz conversion help needed

Check http://groups.yahoo.com/group/MP8K/ and ask that question.
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Old 01-23-2012, 05:32 PM
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Default RE: Kraft 2.4 ghz conversion help needed

not a member
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Old 01-25-2012, 08:31 AM
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Default RE: Kraft 2.4 ghz conversion help needed

Search in here. http://www.rcgroups.com/radios-135/
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Old 01-25-2012, 10:39 AM
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Default 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.

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Old 01-28-2012, 06:11 PM
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Default RE: Kraft 2.4 ghz conversion help needed

that is what I was looking for thanks
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Old 01-28-2012, 07:51 PM
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Default 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.
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Old 01-29-2012, 03:07 AM
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Default RE: Kraft 2.4 ghz conversion help needed

Removing the crystal will stop transmission on 72MHz
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Old 01-30-2012, 09:56 AM
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Default 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...
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Old 01-31-2012, 05:24 PM
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Default RE: Kraft 2.4 ghz conversion help needed

Sorry. Some how I timed out on RCU and it double posted for me
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Old 01-31-2012, 05:26 PM
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Default 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
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Old 02-01-2012, 06:18 PM
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Default 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
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Old 02-20-2012, 11:11 AM
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Default 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
File Type: pdf
Zx70178.pdf (83.6 KB, 123 views)
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Old 02-20-2012, 11:18 AM
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Default RE: Kraft 2.4 ghz conversion help needed

Quote:
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.
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Old 02-20-2012, 11:25 AM
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Default RE: Kraft 2.4 ghz conversion help needed

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